In my experience IF is better thought of as a way to break bad eating habits, not as a direct way to lose weight. Merely eating the same amount of food but in a certain time frame (which is what a lot of people end up doing) doesn’t accomplish much in terms of weight loss.
But I have found it successful in breaking bad habits, which results in weight loss indirectly.
For example, I had a bad habit of eating a large breakfast 1-2 hours within waking up. I was never really that hungry, but it was just something I did out of habit. Doing an IF routine made me realize that I’m not actually that hungry in the morning and can get by until 10-11am on just a coffee with milk.
somenameforme · 5h ago
I'd agree and generalize that intermittent fasting is a great way to remind yourself that that feeling in your stomach when you get hungry doesn't mean you need to eat now. In fact, there's no real rush whatsoever. The first time I did a 24 hour fast, it was brutal and I treated myself to a feast at the end which I rapidly gobbled down.
After doing intermittent fasting for a few years, I have accidentally fasted for 24+ hours multiple times. And after you do it for a while, it makes it clear that this whole modern thing of 3 meals a day, let alone with snacking, is really just weird.
calmbonsai · 3h ago
I'd go further and say adopting any sort of diet regimen is useful for identifying and correcting bad eating habits. Even if the diet ends up being a temporary discipline.
Having any high duty-cycle behavior go from un-tracked to tracked and from (largely) unconscious habitual practice to conscious practice can be a real eye opener.
throwaway290 · 5h ago
Coffee with milk is not breaking IF?
keiferski · 5h ago
I didn’t elaborate enough in my comment. Basically I mean that I stopped eating breakfast with IF and then gradually realized a coffee with milk was enough to serve as a replacement.
The point being that rigidly sticking to IF rules is less useful than just using it as a way to reset your eating habits. (At least in my experience.)
paulpauper · 2h ago
calories= breaking the fast
wenc · 8h ago
I've been doing intermittent fasting (16:8) since 2016 (9 years).
I have a belly and am what you would call "a little chubby". I don't exercise that much (once a week). I drink one black coffee in the morning.
After all these years of IF, net-net I haven't lost any weight, but I find if I stop IF (i.e. I start eating 3 meals a day), I feel sluggish. So in the absence of doing anything else, at least IF keeps my mind sharp.
p.s. the only times I've lost weight is when I've fasted once a week, cut out 50% of all carbs from diet, and starting lifting weights. I lost water weight at first, then plateaued because I gained muscle, then after that muscles did the work of burning excess calories.
I was that way for at least 3 years. Then I decided I loved food too much and added certain carbs back into my diet. These days I just do IF and nothing else, and my weight is stable.
emrahcom · 7h ago
The results are a bit different on my side. I've been doing intermittent fasting (23:1) since 2019 (~6 years). During this period, I did IF (46:2) for a year (one meal every two days).
I have never been overweight in my life but I lost ~10 kg in the first year and my weight has remained stable since then. I haven't measured it, but my body fat percentage is probably around 15%.
By the way I do moderate exercise every days. Walking at very slow speed for 3-4 hours or swimming for an hour. My muscle mass is always increasing, albeit slowly.
HDThoreaun · 7h ago
I do 23:1 and even I think eating every other day is absolutely nuts. Theres no way you are productive the hour before that meal
alexey-salmin · 8h ago
You can try long-distance running. 100km a week allows you to indulge extra 5000-8000k calories.
I also enjoy food and always ate a lot (like 2 meals at lunch), and I was thin all the way up to 30 thanks to fast metabolism I guess. If I didn't start running 5 years ago my choice would be between severe cuts to my diet or obesity.
maccard · 7h ago
I fundamentally think pushing people who want to lose weight into cardio is a mistake. It’s definitely good for you but unless you know how to eat you are going to find yourself over eating very quickly
BigGreenJorts · 6h ago
Been upping my cardio recently for non weight reasons (just want to improve overall endurance for certain sports and heart health) man have I been feeling this. It's crazy how much just a little bit of extra cardio revs up my appetite. It's been about a week and I'm still figuring out how to manage it.
rkomorn · 6h ago
100km/week isn't just "cardio", though. It's a whole lot of it.
I agree that "a little cardio" (eg 30-45 minutes 2-3 times a week) can definitely be counterproductive.
I have to mix in a lot of weight lifting to actually lose weight and offset the appetite creep.
alexey-salmin · 6h ago
I don't know, it's not an easy path but it works more often than fasting for people around me.
Or you're suggesting exercise but of different kind?
maccard · 6h ago
It’s way easier to avoid eating the calories than it is to exercise them off in practice. For most people exercise will cause them to feel hungry, and to eat. I’d you don’t know how much to eat you’ll end up having the wrong effect and gaining weight.
It’s also way easier to just not eat the calories in the first place. A bag of potato chips or a tbsp of nut butter on a rice cake is roughly the equivalent of 15 minutes of running.
Everyone should exercise and move but if it’s for weight loss diet is the way
alexey-salmin · 6h ago
This may be true for real obesity and overeating, but for normal people who just want to lose 5-10 kilos I never saw a diet alone work. They don't eat chips or rice cakes in the first place, their body is in a reasonably healthy equilibrium.
But when you eat less, you just burn less. In the end you're constantly hungry and irritable, you go through all this crap to lose weight and lose none, which doesn't help with the mood either.
At least sport makes you feel good. Dieting without exercise seems to me more like a shortcut into nuthouse.
YZF · 6h ago
I think he's saying you'll compensate by eating more.
Walking might be a better choice but no matter what you do you still need to control the intake of calories.
AstroBen · 7h ago
Getting into cycling actually has me about to stop intermittent fasting. I go out and can burn 1200 calories in a few hours and that's hard to make up with an 8-hour eating window unless I want to start eating a bunch of junk food. Not trying to lose any more weight
rkomorn · 6h ago
Cycling 10-12 hours a week (and going pretty hard at it thanks to the many hills in the Bay Area) let me eat just about everything I wanted while still losing weight.
If you have the time and enjoy it, there's no better way to be able to stuff yourself silly.
zihotki · 5h ago
You can't outrun a bad diet
peterldowns · 7h ago
"Try running 50+ miles a week in order to eat more" is an insane suggestion.
alexey-salmin · 6h ago
Why? Not that it's universally applicable, but if it works for you then why not.
taeric · 8h ago
Did you keep up the weight lifting?
testing22321 · 6h ago
What are you eating?
Soda? Chocolate? Sugar? Ice cream?
You must be eating something extremely calorie dense to be maintaining weight.
Almondsetat · 8h ago
What all these diets are desperately trying to do is psychologically manipulate you into eating less by playing with your sense of fullness. For weight loss, thermodynamics cannot be beaten: eating at different times and in a different order does not matter.
svnt · 8h ago
This is trivially shown to be false.
Imagine a system with a background/quiescent energy consumption of 1000kCal/day.
Imagine that same system can buffer up to 500kCal for up to 24 hours store excess energy in circulation.
Imagine it converts excess energy to stored energy at an efficiency of 50%.
Assume activity correlates with marginal energy consumption but also increases in the presence of excess energy.
A system such as the one described would have very different behaviors during alternate day fasting (0kCal for 24hrs, 5000kCal for 24hrs) than consuming 2500kCal daily.
The human body is more complex than the system I just described, but it is a useful model to consider for this context.
greysphere · 7h ago
Real world efficiency factors are in the 90s and basal rates aren't constant. The model you're proposing is too artificial to draw conclusions about fasting over a short timeframe.
red_trumpet · 7h ago
So, the excess energy in your model is just excreted? Does that also happen in the human body?
wouldbecouldbe · 7h ago
Yes. On the other spectrum, the body becomes more efficient when moving a lot.
rolisz · 8h ago
Unfortunately calories out is a function of calories in.
You eat less calories, your body might start consuming less calories.
Also, there are two different pathways for using glucose in the body: aerobic and anaerobic. The aerobic one produces 15x more ATP (cellular level energy) than the anaerobic one. The anaerobic one wastes more as heat. So if for some reason you're in the second one, even though you ingest the same amount of calories, the amount of energy you have usable is much less.
So yeah, calories in calories out is true, but it's not really helpful.
rkomorn · 7h ago
> So if for some reason you're in the second one, even though you ingest the same amount of calories, the amount of energy you have usable is much less.
This is technically true but not particularly relevant.
It's quite difficult to be in only anaerobic effort, though (and I'd say pretty ill advised since that basically means stuff like all out sprinting without warmup or cooldown).
Higher intensity effort burns more calories than lower intensity (eg [1]). It's just harder to sustain.
Calories in / Calories out might be broadly accurate, but reality is a lot more complicated than that. People are really bad at tracking how many calories they take in. Its impossible to measure how many calories you're actually exerting with exercise. Its even more impossible to measure how many calories you pee, poop, perspire, breathe, and radiate out. Microvariations across your current body state, body temperature, and even the time of day can influence how efficient your gut is at absorbing incoming energy.
Some people operate with a goal of a caloric deficit of even something as small as e.g. 200kcal. But because all these things are impossible to measure accurately, a difference of just 10% beyond a daily BMR of 2000kcal isn't just a possibility; its the norm. You run for an hour; what if that burns an extra 50kcal that your Apple Watch did not account for? You eat a slice of bread which advertises it contains 80kcal; but it actually contains 100kcal [1]? You sleep poorly, which causes some mild systemic inflammation the next day, which raises your body temperature?
The really cool part is you don’t have to accurately track how many calories go in and out. The proof is in the pudding.
If you had a car with a broken gas gauge you would just pump until it overflowed… same idea here.
Over a month or so if your weight is stable then you are putting in as many calories as you burn. If you’re gaining weight, you’re consuming more, and if you’re losing weight, you’re consuming less.
Adjust accordingly.
827a · 6h ago
Sure, but no one can actually do that accurately, for the aforementioned reasons. "I'm gaining weight; I should eat less": How do you structure that in a way that's actually actionable and drive results? Just a general sense that "eh I should eat less"? No one eats consistently enough, or exerts energy consistently enough, to actually make vibe-structuring cal-in/cal-out possible. You might think "I should work out more, that's more calories out" -> but ask literally any runner about how running affects their appetite and you'll realize quickly how wrong that is.
Hence: Why diets exist. That is the structure. There are good ones and bad ones.
Keto, for example, can work for weight loss not because there's anything particularly interesting about the way your body absorbs carbs versus protein and fat (there are differences, but its not the biggest reason why it can work). It can work for some people because typical protein and fat food sources are less calorically dense (by volume and weight) than carb sources. You may feel full faster; so you may naturally eat fewer calories.
Similarly: IF can work for some people because most people cannot physically eat enough to consume massive calorie counts if they time-restrict the hours they're allowed to eat. It also seems to come with some well-studied metabolic effects.
You don't have to accurately track inflows and outflows, but vibe-structuring your consumption and exertion habits based on outcomes is a privilege that, sure, some people have, but is not a panacea for every body and mind. Broadly, the people who need to make change who do this will not see the change they wanted.
testing22321 · 4h ago
> No one eats consistently enough, or exerts energy consistently enough, to actually make vibe-structuring cal-in/cal-out possible
Of course we do!
You’re thinking of this the wrong way. The goal isn’t “eat less” as you said, it’s “consume less calories (energy)”
On any given month if you gain weight or maintain when you want to lose, then you need to consume less energy next month. For 99% of people, that means reduce sofa, reduce sugar, reduce fat (all the energy dense stuff)
Feeling hungry? Drink massive glasses of water and eat literally all the vegetables you physically can get in. I have whole carrots for snacks most days. Cauliflower too. Cucumber is great. Frozen peas on a hot day. All of it, as much as you can eat.
827a · 3h ago
You can feel that if you want, but the data is clear: 73% of Americans are overweight. Its not easy to lose weight. Managing caloric intake is hard. Eating the right things is hard. Activity is hard. Suggesting that structured systems, backed by science, which help achieve these goals are unnecessary conveniently ignores both the reality of America's weight issue, and the myriad of success stories many individuals have had leveraging these structured systems to meet their goals.
testing22321 · 31m ago
At no point did I say it’s easy. I said it simple. They are not the same.
Also note Americans are more obese than the rest of the world. Like gun violence, police deaths, healthcare and so much more - the rest of the world can fix it. Why not America.
somenameforme · 5h ago
You're overestimating the difficulty here. You don't really need to wait a month either. There's plenty of variance on a day by day basis, but you can still generally see whether the number is trending up or down. And most people tend to cycle through the same foods, so portion control isn't particularly hard.
For instance this is something every single person who's into body building does, because you want to be in a slight caloric surplus when bulking, and then you want to get back into a slight calorific deficit when cutting.
calmbonsai · 3h ago
Oh my NO! Just...no.
It turns out the body processes different calories very differently depending on a variety of factors including: baseline genetics, time of day, menstrual cycle, prior fasting, current mineral excess/debt, gut flora/fauna biome, and the composition of previously consumed food still remaining the digestive track.
flyinglizard · 8h ago
You’re assuming the body is a constant machine that metabolizes at a fixed rate but that can’t be true.
tekla · 8h ago
Until the human body becomes capable of creating energy out of nothing, this is irrelevant
alexey-salmin · 8h ago
It's not. Human body can't create energy out of nothing, but it can vary the consumption of energy in a wide range which is very similar in terms of externally observable effects.
It's a common story when people start to eat 20% less, continue the same lifestyle and lose exactly zero weight as the result. Their body didn't create 20% of energy out of nothing but it just started to waste less energy as body heat.
maccard · 6h ago
20%? That’s 4-500 calories a day less. Have you hit any links to this as it’s a pretty wild claim
tekla · 7h ago
Irrelevant, energy out > energy in, you lose weight
iteria · 6h ago
They have literally done studies showing that this is a naive take. You might lose weight, but the literal moment you consume more calories your body stores every stray calorie it can and it battles you about loses weight every moment. Your body will save calories to the point of discomfort and ill health. The impacts of extreme calorie deficits last for extremely long times and bias your body towards weight gain.
The body is more like a thermostat system. Environmental effects can convince your body to move the temperature/weight up or down, but for both weight gain and weight loss is a battle. Your body tries to maintain it's understood ideal weight. Your body if given a chance and you haven't convinced it to change the thermostat setting, will immediately do all it can to gain/loose weight. This is why crash diets never work. It takes sustained effort to convince your body that it's wrong about your initial weight.
tekla · 6h ago
They have literally done studies that show people who claim they can't lose weight are vastly underestimating the amount of calories they eat.
These are excuses, in the fitness community, the response to "I can't lose weight" is "eat fewer calories", and its incredibly effective
827a · 6h ago
How are you measuring energy out, such that it can directly influence decisions on how much energy you should be deciding to take in? I promise you: Your methodology is inaccurate.
alexey-salmin · 7h ago
The latter is true, the former is not.
Anything that can influence "energy out" is by your own definition "relevant".
californical · 8h ago
It can use different amounts of energy depending on different stimulus. Things like fidgeting and body temperature can make a pretty decent difference
anon84873628 · 7h ago
Just to add some color for folks, this is referred to as NEAT in the literature: Non-Exercise Activity and Thermogenesis.
When caloric intake is reduced, the body can decrease this type of expenditure without the person even realizing it.
objektif · 8h ago
Very bad take. What if our bodies adjusts the burn rate based on when we eat when we exercise? if that is true you can potentially eat more and lose more weight.
tekla · 7h ago
Irrelevant, energy out > energy in, you lose weight
IncreasePosts · 5h ago
Okay, and energy in affects energy out. What you are saying is true and useless.
HDThoreaun · 7h ago
energy out changes though. By focusing only on energy in you miss half the equation
tekla · 6h ago
Last time I checked, I don't control my metabolism with a dial. I do control what enters my body through my mouth
IncreasePosts · 6h ago
This is an entirely useless thing to say. Your body can make choices, based on what and when and how you eat, that you can't control with your psychology.
Your body can raise or lower its temperature. It can put energy towards cell repair or cell reproduction. It can store energy as fat, or signal to burn fat, or build muscle or catabolize muscle.
BennyH26 · 8h ago
In our medical practice, we would use intermittent fasting as part of a comprehensive medical plan to increase longevity. There are studies which demonstrate this is beneficial, at least in Macaque monkeys. Weight loss was just a nice side effect.
anon84873628 · 7h ago
As Mike Israetel puts it, you don't want your body swimming in nutrients all day every day.
Whether it's IF, deficit cycles, periodic deep fast -- they all seem to have the same effect, which is just to give the body a break for a bit.
surfsvammel · 7h ago
I diet, on and off. Keeping fat free weight as the highest priority (I don’t want to loose hard earned muscle)!
I’ve tried all types of diets. For me, the most important for me is to save the biggest meal for late in the day. I can easily go hungry a couple of hours during the day if I know there is a filling meal coming.
I suspect IF works in a similar way.
strken · 8h ago
I'm not sure that a reduction in body weight tells us all the relevant information. One of the possible downsides of fasting is loss of lean body mass, generally meaning muscle. This is a problem for older people in particular because it's harder to keep muscle as you age and because muscle protects from falls, frailty, etc.
testing22321 · 8h ago
If a person is obese or morbidly obese, losing weight is the number one priority to increase overall health, lifespan, quality of life, etc etc.
Losing a bit of lean muscle mass along the way is not important compared to the huge health gains of losing the weight.
AstroBen · 8h ago
I don't think this is specific to fasting?
You need to be getting enough protein + strength training to maintain muscle in a caloric deficit
Someone1234 · 8h ago
Weight loss is linked with some loss of lean body mass, regardless of the method used. Intermittent fasting has been shown to match any other calorie deficit in terms of lean body mass loss, rather than more as you're implying.
Regardless of how you lose weight the advice is and remains:
> Eat a minimum of 0.36 grams of protein per day, per pound of LEAN* body weight. Increasing to 0.5-0.7 grams of protein per day, per pound of LEAN* body weight for older adults or when undergoing weight loss.
*LEAN is a vital detail for overweight people, they commonly miscalculate protein requirements due to this. The easiest way for overweight people to determine their requirement, is just find an "ideal body weight calculator" online, enter height and gender, and then multiply THAT figure by 0.5-0.7.
For example a man who is 6' tall and 400 lbs should eat 62 grams of protein per day MINIMUM, but during weight loss 86-120 grams of protein per day. It is common, unfortunately, to read online people in this situation miscalculate this to 280(!) grams of protein per day which is incorrect and harms their weight-loss goals.
funcDropShadow · 7h ago
Do you have source for this? Because as you write I've always read to derive protein intake from the overall weight. That would indeed be a very important distance.
Someone1234 · 1h ago
Yep, it is often repeated bad advice that was originally aimed at healthy weight adults and athletes and then misunderstood by people attempting to lose body fat. It is incorrectly repeated on hundreds of exercise sites and articles. Cite:
> Protein intake should range between 1.0-1.5 grams/kg of adjusted body weight. To calculate adjusted body weight, first calculate excess weight: Excess weight = current weight — ideal body weight (IBW). Adjusted body weight = IBW + 0.25 of excess body weight. This amount generally accounts for 20% to 30% of total caloric intake.
So a slightly more complex way of calculating roughly the same thing. I'd argue that for most people getting your ideal weight is a good enough approximation, and that using your overweight/obese body fat in your protein calculation is wrong by a lot no matter which calculation you use.
I did intermittent fasting. I think this conditioned me to being in the hunger state and to ignore hunger. Along with exercise and portion control, I did lose 20 pounds. I could have gone further but I became lacking in certain nutrients and a doctor told me to stop.
mrbonner · 7h ago
I’m curious whether taking the oral form of Ozempic at a lower dose could have effects similar to intermittent fasting, given that it may lead to skipping a meal as well.
kaycebasques · 7h ago
Microdosing ozempic
gorfian_robot · 6h ago
Diet Coke now with GLPs?
garrickvanburen · 7h ago
After briefly looking into it, my assumption is intermittent fasting works great for people that are eating throughout the entirety of the day.
abracadaniel · 7h ago
I’ve often wondered about this. If you have a sugary drink, would it be better to drink it in one sitting or sip it throughout the day.
bonvoiay · 6h ago
It surprises me how often the basic physiology still gets overlooked.
Hunger is driven by hormonal signals designed to defend a set point. Even if you consciously fast for most of the day, your brain will push you to make up the difference once you start eating. When it comes to fat loss, it still boils down to maintaining a caloric deficit — timing alone won’t keep your appetite in check for long. We’ve known this for years.
IF may have other potential benefits — better insulin sensitivity, longevity, or improved adherence for some people (since avoiding food most of the day can be psychologically easier) — but none of that is “new” anymore.
lkrubner · 7h ago
I have read that before the Industrial Revolution, most people faced famine for about 10% of their lives. And while, historically, that would have probably been concentrated into a few bad years during their lifetime (months of starvation, during a few bad years), if we were to generalize that and make it a rule, it would work out to 3 days a month.
There is some evidence that there are health benefits that are specific to the fasting mode. This has mostly been studied in the context of chemotherapy, where fasting can protect against some of the side-effects of chemotherapy:
Most of this has only been studied in animals, not humans, but in animals the results were clear:
"Fasting before chemotherapy (CT) was shown to protect healthy cells from treatment toxicity by reducing the expression of some oncogenes, such as RAS and the AKT signaling pathway [2]. This reduction is mediated by the decrease of circulating insulin-like growth factor 1 (IGF-1) and glucose. In addition, starvation and calorie restriction activate other oncogenes in cancer cells, induce autophagy, and decrease cellular growth rates while increasing sensitivity to antimitotic drugs [2]."
If we assume that we have been shaped by millions of years of frequent famine, then our evolution has been shaped by famine. It is possible that our immune system simply makes the assumption that we will soon face famine, and therefore some important tasks, such as extreme autophagy, are normally postponed till the famine arrives. However, in the modern era the famine never arrives, and so we may have to induce it by artificial means.
I have experimented with very long fasts. My longest fast ever was in September of 2015 when I managed to go 12 straight days on nothing but water.
Obviously, any health benefits from that incident might have been psychosomatic, since I was expecting health benefits. But all the same, I did find some of the health benefits to be shocking and completely unexpected. Since at least 1995, and possibly 1990, I had a mole on my skin on my left arm. I wasn't worried about it, so I simply ignored it. I had it on my arm at least 20 years, maybe 25 years. I recall one morning in November of 2015 when I was in my kitchen, making breakfast, and I reached over to pour myself some coffee, and of course my arm was in my field of vision, and after a moment of thinking something was different, it occurred to me that the mole was gone. It had been there at least 20 years, and then it disappeared, at some point during the weeks after I had done the 12 day fast. I don't know when it disappeared, it just slowly faded away at some point between September and November. There was no remaining sign of it on my arm.
Again, that might have been purely psychosomatic, but it was interesting.
ellen364 · 6h ago
Admittedly a minor point of interest, but the last famine in England happened in 1623 and was local to an area called Westmorland [0]. That was 150 years before the Industrial Revolution, so the 10% figure might not be very reliable.
England was the first nation to escape from famine. A national market began to take shape shortly after the civil war, and the national market transformed traditional famine into a question of high prices. Jethro Tull began his experiments in 1701, and Charles Townsend began taking notes about fertilizer shortly afterwards, and when the public became aware of their work, the Agricultural Revolution began, and then, shortly afterwards, the Industrial Revolution. But obviously, most of the world continued to experience famine into the 1900s.
alchemist1e9 · 7h ago
Are you religious or spiritual in any way and if so was there a connection to that and your twelve days water fast?
1024core · 8h ago
Every study ends with something along the lines of:
Longer duration trials are needed to further substantiate these findings.
pdxandi · 7h ago
I read that as needing funding. Somebody has to pay for the research. In order to get it funded, you have to show your research has a basis. My interpretation anyway.
mrandish · 5h ago
N=1 but in 2017 I lost over 100 pounds in 8 months by changing to a keto + IF diet and I've kept it off. I lost 10 pounds in 10 days and 20 pounds the first month. At around six weeks I became 'fat-adapted', a long-term metabolic transition to primarily burning fat instead of carbs (glucose) for energy. I didn't start with IF but at around that point I sort of fell into intermittent fasting because it just felt right. I'd heard about IF but never had it as a goal because it seemed impossible since I'd been hungry my whole life. But limiting carbs with keto controlled my blood sugar to the extent I was almost never hungry which made IF trivially easy. So if you're trying IF and struggling with hunger pangs, try managing blood sugar by reducing carb intake.
The combination of Keto+IF worked so well for me, for a while my calorie tracking switched from the usual preventing eating too many calories to ensuring I was getting enough, which was certainly never on my bingo card. After a lifetime of being a slave to hunger it was liberating to suddenly feel effortlessly in control of diet and my relationship with food changed completely. Then at around 90 days my palate shifted, meaning I even lost my taste for carbie foods. If I tried a small bite of something carb-laden that I'd loved my whole life, it didn't even taste particularly good to me anymore. I also became hyper-sensitive to sugar. Sugar-soaked foods just taste poisonously over-sweetened (which they kind of are). A slice of apple now tastes as sweet as I'd ever want, like a dessert that has extra sugar-added.
In the 8th month I reached below my ideal 'dream' weight and even saw abs appear for the first time in my life! I transitioned to maintenance mode but stayed keto because being in a blood sugar controlled state felt so amazing and not just physically but also mentally and emotionally. At around a year I went from strict keto to low carb for life which I still am 8 years later. When I started that was unimaginable. I saw keto as an onerous regimen that I'd endure if it worked and stop the second I wasn't overweight. But during the journey my metabolism, palate and food preferences changed so dramatically, I was basically a different person when I arrived. Those first few months when I was rigorously tracking every calorie in an app and managing intake with measuring cups and a kitchen scale felt like a burden but were actually invaluable skill-building. After a few months all that process became automatic so I didn't need to constantly track and by six months I got to the point where I don't even think about it consciously. That early rigor helped me get so in sync with my body and able to sense where my metabolism is in its natural cycles that now I just eat when necessary and convenient for my schedule. This often ends up being IF but it's not intentional on my part, which makes me think maybe IF patterns evolved in the hunter/gatherer era as part of our natural biological rhythms. Due to habit and carb-laden factory foods I'd never been able to access those rhythms until I made the conscious effort to break the patterns I'd been raised in.
porridgeraisin · 6h ago
Practical advice for people who do normal 80/20 healthy/unhealthy stuff and don't wanna think:
Now and then like twice a month, skip 2/3 meals in the day. If hard, have light juices/even fruits. Think of it as giving your digestive system "rest". Don't do it when otherwise sick.
It will make you generally healthier, no drastic changes. Those require drastic measures which differ person to person.
bargainbin · 8h ago
The takeaway here is that if you do “alternate day fasting”, that is you eat normally on one day then do not eat all the next, you will lose weight.
I can’t believe that losing 3.5 days of caloric intake would result in weight loss. In other news, water is wet.
m4r71n · 8h ago
Alternate day fasting normally means you eat up to 500 calories on your fasting day, but then eat more than usual on normal days. So on average if you eat 500 one day and 2500 another, that is no different than eating a restricted diet of 1500 every day. The finding here is that the former results in slightly more weight loss than the latter. That restrictions in calorie intake will result in weight loss is a given.
scns · 8h ago
> eating a restricted diet of 1500
Keeping this up is hard, many fail. Alternating normal eating with IF days is easier to do.
layer8 · 6h ago
No, the takeaway is that it results in more weight loss than intermittent fasting and whole-day fasting.
fred_is_fred · 8h ago
Or if you just ate 50% less calories 7 days a week perhaps.
treetalker · 8h ago
My understanding is that, yes, the weight loss results end up being similar — but that the story is not so simple (or linear) because "true" fasting activates certain metabolic pathways (e.g., mTOR) that mere calorie reduction does not, and that those pathways have different effects, such as autophagy and others that increase lifespan in different ways.
But I have found it successful in breaking bad habits, which results in weight loss indirectly.
For example, I had a bad habit of eating a large breakfast 1-2 hours within waking up. I was never really that hungry, but it was just something I did out of habit. Doing an IF routine made me realize that I’m not actually that hungry in the morning and can get by until 10-11am on just a coffee with milk.
After doing intermittent fasting for a few years, I have accidentally fasted for 24+ hours multiple times. And after you do it for a while, it makes it clear that this whole modern thing of 3 meals a day, let alone with snacking, is really just weird.
Having any high duty-cycle behavior go from un-tracked to tracked and from (largely) unconscious habitual practice to conscious practice can be a real eye opener.
The point being that rigidly sticking to IF rules is less useful than just using it as a way to reset your eating habits. (At least in my experience.)
I have a belly and am what you would call "a little chubby". I don't exercise that much (once a week). I drink one black coffee in the morning.
After all these years of IF, net-net I haven't lost any weight, but I find if I stop IF (i.e. I start eating 3 meals a day), I feel sluggish. So in the absence of doing anything else, at least IF keeps my mind sharp.
p.s. the only times I've lost weight is when I've fasted once a week, cut out 50% of all carbs from diet, and starting lifting weights. I lost water weight at first, then plateaued because I gained muscle, then after that muscles did the work of burning excess calories.
I was that way for at least 3 years. Then I decided I loved food too much and added certain carbs back into my diet. These days I just do IF and nothing else, and my weight is stable.
I have never been overweight in my life but I lost ~10 kg in the first year and my weight has remained stable since then. I haven't measured it, but my body fat percentage is probably around 15%.
By the way I do moderate exercise every days. Walking at very slow speed for 3-4 hours or swimming for an hour. My muscle mass is always increasing, albeit slowly.
I also enjoy food and always ate a lot (like 2 meals at lunch), and I was thin all the way up to 30 thanks to fast metabolism I guess. If I didn't start running 5 years ago my choice would be between severe cuts to my diet or obesity.
I agree that "a little cardio" (eg 30-45 minutes 2-3 times a week) can definitely be counterproductive.
I have to mix in a lot of weight lifting to actually lose weight and offset the appetite creep.
Or you're suggesting exercise but of different kind?
It’s also way easier to just not eat the calories in the first place. A bag of potato chips or a tbsp of nut butter on a rice cake is roughly the equivalent of 15 minutes of running.
Everyone should exercise and move but if it’s for weight loss diet is the way
But when you eat less, you just burn less. In the end you're constantly hungry and irritable, you go through all this crap to lose weight and lose none, which doesn't help with the mood either.
At least sport makes you feel good. Dieting without exercise seems to me more like a shortcut into nuthouse.
Walking might be a better choice but no matter what you do you still need to control the intake of calories.
If you have the time and enjoy it, there's no better way to be able to stuff yourself silly.
Soda? Chocolate? Sugar? Ice cream?
You must be eating something extremely calorie dense to be maintaining weight.
Imagine a system with a background/quiescent energy consumption of 1000kCal/day.
Imagine that same system can buffer up to 500kCal for up to 24 hours store excess energy in circulation.
Imagine it converts excess energy to stored energy at an efficiency of 50%.
Assume activity correlates with marginal energy consumption but also increases in the presence of excess energy.
A system such as the one described would have very different behaviors during alternate day fasting (0kCal for 24hrs, 5000kCal for 24hrs) than consuming 2500kCal daily.
The human body is more complex than the system I just described, but it is a useful model to consider for this context.
You eat less calories, your body might start consuming less calories.
Also, there are two different pathways for using glucose in the body: aerobic and anaerobic. The aerobic one produces 15x more ATP (cellular level energy) than the anaerobic one. The anaerobic one wastes more as heat. So if for some reason you're in the second one, even though you ingest the same amount of calories, the amount of energy you have usable is much less.
So yeah, calories in calories out is true, but it's not really helpful.
This is technically true but not particularly relevant.
It's quite difficult to be in only anaerobic effort, though (and I'd say pretty ill advised since that basically means stuff like all out sprinting without warmup or cooldown).
Higher intensity effort burns more calories than lower intensity (eg [1]). It's just harder to sustain.
1- https://www.webmd.com/fitness-exercise/what-to-know-heart-ra... )
Food — not lack of exercise — fuels obesity, study finds
https://www.npr.org/2025/07/24/nx-s1-5477662/diet-exercise-o...
Some people operate with a goal of a caloric deficit of even something as small as e.g. 200kcal. But because all these things are impossible to measure accurately, a difference of just 10% beyond a daily BMR of 2000kcal isn't just a possibility; its the norm. You run for an hour; what if that burns an extra 50kcal that your Apple Watch did not account for? You eat a slice of bread which advertises it contains 80kcal; but it actually contains 100kcal [1]? You sleep poorly, which causes some mild systemic inflammation the next day, which raises your body temperature?
[1] https://health.clevelandclinic.org/are-calorie-counts-accura...
If you had a car with a broken gas gauge you would just pump until it overflowed… same idea here.
Over a month or so if your weight is stable then you are putting in as many calories as you burn. If you’re gaining weight, you’re consuming more, and if you’re losing weight, you’re consuming less.
Adjust accordingly.
Hence: Why diets exist. That is the structure. There are good ones and bad ones.
Keto, for example, can work for weight loss not because there's anything particularly interesting about the way your body absorbs carbs versus protein and fat (there are differences, but its not the biggest reason why it can work). It can work for some people because typical protein and fat food sources are less calorically dense (by volume and weight) than carb sources. You may feel full faster; so you may naturally eat fewer calories.
Similarly: IF can work for some people because most people cannot physically eat enough to consume massive calorie counts if they time-restrict the hours they're allowed to eat. It also seems to come with some well-studied metabolic effects.
You don't have to accurately track inflows and outflows, but vibe-structuring your consumption and exertion habits based on outcomes is a privilege that, sure, some people have, but is not a panacea for every body and mind. Broadly, the people who need to make change who do this will not see the change they wanted.
Of course we do!
You’re thinking of this the wrong way. The goal isn’t “eat less” as you said, it’s “consume less calories (energy)”
On any given month if you gain weight or maintain when you want to lose, then you need to consume less energy next month. For 99% of people, that means reduce sofa, reduce sugar, reduce fat (all the energy dense stuff)
Feeling hungry? Drink massive glasses of water and eat literally all the vegetables you physically can get in. I have whole carrots for snacks most days. Cauliflower too. Cucumber is great. Frozen peas on a hot day. All of it, as much as you can eat.
Also note Americans are more obese than the rest of the world. Like gun violence, police deaths, healthcare and so much more - the rest of the world can fix it. Why not America.
For instance this is something every single person who's into body building does, because you want to be in a slight caloric surplus when bulking, and then you want to get back into a slight calorific deficit when cutting.
It turns out the body processes different calories very differently depending on a variety of factors including: baseline genetics, time of day, menstrual cycle, prior fasting, current mineral excess/debt, gut flora/fauna biome, and the composition of previously consumed food still remaining the digestive track.
It's a common story when people start to eat 20% less, continue the same lifestyle and lose exactly zero weight as the result. Their body didn't create 20% of energy out of nothing but it just started to waste less energy as body heat.
The body is more like a thermostat system. Environmental effects can convince your body to move the temperature/weight up or down, but for both weight gain and weight loss is a battle. Your body tries to maintain it's understood ideal weight. Your body if given a chance and you haven't convinced it to change the thermostat setting, will immediately do all it can to gain/loose weight. This is why crash diets never work. It takes sustained effort to convince your body that it's wrong about your initial weight.
These are excuses, in the fitness community, the response to "I can't lose weight" is "eat fewer calories", and its incredibly effective
Anything that can influence "energy out" is by your own definition "relevant".
When caloric intake is reduced, the body can decrease this type of expenditure without the person even realizing it.
Your body can raise or lower its temperature. It can put energy towards cell repair or cell reproduction. It can store energy as fat, or signal to burn fat, or build muscle or catabolize muscle.
Whether it's IF, deficit cycles, periodic deep fast -- they all seem to have the same effect, which is just to give the body a break for a bit.
I’ve tried all types of diets. For me, the most important for me is to save the biggest meal for late in the day. I can easily go hungry a couple of hours during the day if I know there is a filling meal coming.
I suspect IF works in a similar way.
Losing a bit of lean muscle mass along the way is not important compared to the huge health gains of losing the weight.
You need to be getting enough protein + strength training to maintain muscle in a caloric deficit
Regardless of how you lose weight the advice is and remains:
> Eat a minimum of 0.36 grams of protein per day, per pound of LEAN* body weight. Increasing to 0.5-0.7 grams of protein per day, per pound of LEAN* body weight for older adults or when undergoing weight loss.
*LEAN is a vital detail for overweight people, they commonly miscalculate protein requirements due to this. The easiest way for overweight people to determine their requirement, is just find an "ideal body weight calculator" online, enter height and gender, and then multiply THAT figure by 0.5-0.7.
For example a man who is 6' tall and 400 lbs should eat 62 grams of protein per day MINIMUM, but during weight loss 86-120 grams of protein per day. It is common, unfortunately, to read online people in this situation miscalculate this to 280(!) grams of protein per day which is incorrect and harms their weight-loss goals.
> Protein intake should range between 1.0-1.5 grams/kg of adjusted body weight. To calculate adjusted body weight, first calculate excess weight: Excess weight = current weight — ideal body weight (IBW). Adjusted body weight = IBW + 0.25 of excess body weight. This amount generally accounts for 20% to 30% of total caloric intake.
So a slightly more complex way of calculating roughly the same thing. I'd argue that for most people getting your ideal weight is a good enough approximation, and that using your overweight/obese body fat in your protein calculation is wrong by a lot no matter which calculation you use.
https://www.ajmc.com/view/chapter-2-clinical-nutrition-guide...
Hunger is driven by hormonal signals designed to defend a set point. Even if you consciously fast for most of the day, your brain will push you to make up the difference once you start eating. When it comes to fat loss, it still boils down to maintaining a caloric deficit — timing alone won’t keep your appetite in check for long. We’ve known this for years.
IF may have other potential benefits — better insulin sensitivity, longevity, or improved adherence for some people (since avoiding food most of the day can be psychologically easier) — but none of that is “new” anymore.
There is some evidence that there are health benefits that are specific to the fasting mode. This has mostly been studied in the context of chemotherapy, where fasting can protect against some of the side-effects of chemotherapy:
https://pmc.ncbi.nlm.nih.gov/articles/PMC5870384/
Most of this has only been studied in animals, not humans, but in animals the results were clear:
"Fasting before chemotherapy (CT) was shown to protect healthy cells from treatment toxicity by reducing the expression of some oncogenes, such as RAS and the AKT signaling pathway [2]. This reduction is mediated by the decrease of circulating insulin-like growth factor 1 (IGF-1) and glucose. In addition, starvation and calorie restriction activate other oncogenes in cancer cells, induce autophagy, and decrease cellular growth rates while increasing sensitivity to antimitotic drugs [2]."
If we assume that we have been shaped by millions of years of frequent famine, then our evolution has been shaped by famine. It is possible that our immune system simply makes the assumption that we will soon face famine, and therefore some important tasks, such as extreme autophagy, are normally postponed till the famine arrives. However, in the modern era the famine never arrives, and so we may have to induce it by artificial means.
I have experimented with very long fasts. My longest fast ever was in September of 2015 when I managed to go 12 straight days on nothing but water.
Obviously, any health benefits from that incident might have been psychosomatic, since I was expecting health benefits. But all the same, I did find some of the health benefits to be shocking and completely unexpected. Since at least 1995, and possibly 1990, I had a mole on my skin on my left arm. I wasn't worried about it, so I simply ignored it. I had it on my arm at least 20 years, maybe 25 years. I recall one morning in November of 2015 when I was in my kitchen, making breakfast, and I reached over to pour myself some coffee, and of course my arm was in my field of vision, and after a moment of thinking something was different, it occurred to me that the mole was gone. It had been there at least 20 years, and then it disappeared, at some point during the weeks after I had done the 12 day fast. I don't know when it disappeared, it just slowly faded away at some point between September and November. There was no remaining sign of it on my arm.
Again, that might have been purely psychosomatic, but it was interesting.
[0] https://bahs.org.uk/AGHR/ARTICLES/59_23_Healey.pdf
Longer duration trials are needed to further substantiate these findings.
The combination of Keto+IF worked so well for me, for a while my calorie tracking switched from the usual preventing eating too many calories to ensuring I was getting enough, which was certainly never on my bingo card. After a lifetime of being a slave to hunger it was liberating to suddenly feel effortlessly in control of diet and my relationship with food changed completely. Then at around 90 days my palate shifted, meaning I even lost my taste for carbie foods. If I tried a small bite of something carb-laden that I'd loved my whole life, it didn't even taste particularly good to me anymore. I also became hyper-sensitive to sugar. Sugar-soaked foods just taste poisonously over-sweetened (which they kind of are). A slice of apple now tastes as sweet as I'd ever want, like a dessert that has extra sugar-added.
In the 8th month I reached below my ideal 'dream' weight and even saw abs appear for the first time in my life! I transitioned to maintenance mode but stayed keto because being in a blood sugar controlled state felt so amazing and not just physically but also mentally and emotionally. At around a year I went from strict keto to low carb for life which I still am 8 years later. When I started that was unimaginable. I saw keto as an onerous regimen that I'd endure if it worked and stop the second I wasn't overweight. But during the journey my metabolism, palate and food preferences changed so dramatically, I was basically a different person when I arrived. Those first few months when I was rigorously tracking every calorie in an app and managing intake with measuring cups and a kitchen scale felt like a burden but were actually invaluable skill-building. After a few months all that process became automatic so I didn't need to constantly track and by six months I got to the point where I don't even think about it consciously. That early rigor helped me get so in sync with my body and able to sense where my metabolism is in its natural cycles that now I just eat when necessary and convenient for my schedule. This often ends up being IF but it's not intentional on my part, which makes me think maybe IF patterns evolved in the hunter/gatherer era as part of our natural biological rhythms. Due to habit and carb-laden factory foods I'd never been able to access those rhythms until I made the conscious effort to break the patterns I'd been raised in.
Now and then like twice a month, skip 2/3 meals in the day. If hard, have light juices/even fruits. Think of it as giving your digestive system "rest". Don't do it when otherwise sick.
It will make you generally healthier, no drastic changes. Those require drastic measures which differ person to person.
I can’t believe that losing 3.5 days of caloric intake would result in weight loss. In other news, water is wet.
Keeping this up is hard, many fail. Alternating normal eating with IF days is easier to do.