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I’ve been doing IF with some interruptions for about 10 years. It’s absolutely changed my life because before that I was steadily gaining about 5-20lbs per year and it had really added up over my 20s. Now I’m 39 in the best shape of my life.

So I’m invested in this technique, but I really believe the primary and possibly exclusive benefit is simply calorie restriction.

In a typical “diet” you attempt to restrict calories by remove foods from your diet. The problem is, cravings are real, abstinence doesn’t work, and there are always new foods and new temptations.

On an IF regimen, you restrict calories by removing eating hours from your day. You don’t have to abstain from anything. Temptation is managed by just having a little patience until your next meal.

Possibly there is a deeper truth to why this lifestyle works but I personally like the simplicity of it.

It’s like a rate limiter, for daily food intake.

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I used to be way overweight. A few years ago I lost a lot of weight by basically walking a lot and doing intemittent fasting.

Then I stopped it and started to slowly gain more weight. Now I'm on an IF regiment again.

Now, I really doubt it's the calorie restriction that's at work here.

The human body is not a simple physical machine. It's a complex system.

A simple machine would be some like like a car that has a set amount of energy needed and simple mechanism to switch energy source when one of them is almost depleted.

A complex machine is one that responds to the environment and changes its internal behavior. For example, it can decide to activate or shutdown internal systems that use energy in order to conserve energy. It can decide to let go of conserving energy and just make sure the body has a lot of energy for performing the current activity.

Common wisdom says that the body goes in hunger mode if you restrict calories. But I don't think that's what's going on. Because you also restrict calories on IF. Instead I think that when you consistently eat low calorie meals, it activates some mechanism in your body that's meant to conserve energy when you are living through some sort of a famine, or something like that. (another possibility: instead of a famine, it thinks you became a low status individual within your tribe). But when you do IF you typically eat normal size, filling meals, so this mechanism never gets triggered. Further more, there's probably no mechanism in your brain that thinks that going for many hours without food is a bad thing. Quite the opposite: it's just the normal expected thing.

So if you do some exercise while in a fasted state, even though you are technically low on calories, your brain probably thinks you might be hunting for food so it will make sure you can utilize all the energy you need and some more.

> The problem is, cravings are real, abstinence doesn’t work,

I'm not sure what you mean here? Surely fasting is abstinence, is it not?

You can at any time decide to open the fridge and eat something. You can decide at any time to go to the nearby convenience store and buy something to eat.

There are studies on this and, from what I can remember, meal frequency didn't seem to have an impact on weight loss or muscle gain.

You don't need to eat 6 meals or 1 per day to lose weight, just do whatever makes it easy for you to consume the amount of calories you want.

I agree that doing 1-2 big meal makes it easier to eat little calories because you can stuff yourself up to a point.

> There are studies on this

Studies on this are generally poor quality, and you can easily tell by looking at the study content.

Remember when early 2020 all the official organizations (WHO, CDC) were telling people to NOT wear masks because studies showed they didn't work? Yea. Turned out all the studies were really bad quality.

"Scientific" publishing is broken and you simply can't rely on it for useful information. Many studies don't even replicate, but they still get published and cited.

For another example, see: https://twitter.com/cmuratori/status/1459275924059217920

Basically, whenever I hear "studies have shown ..." I just don't care. Let the studies show whatever they want. I will go with my own experience and with personal anecdotes I hear from people. They are way more consistent and reliable.

> "Scientific" publishing is broken and you simply can't rely on it for useful information. Many studies don't even replicate, but they still get published and cited.

I may take issue with some of your other statements but fully agree with this observation.

A critical thinker needs to be highly skeptical of the appeal to authority used by invoking the phrases “the science says”, or “studies have shown”.

Maybe not but low blood sugar has a high impact on hunger and can cause a slowdown of the metabolism. If you eat a normal diet but less often you get way more hungry and burn less calories. If your 1-2 meals are high on carbs you will quickly either get extreme hunger or go into starvation mode. The dreaded yo-yo effect.

Yes I agree with you. Body does not go into starvation mode during IF. One meal a day is ideal.

My eating window is around 4-8pm most days the last 6 months. Usually just one meal of literally anything I want and Im still finding I have to eat more to stop losing weight.

I'll never understand OMAD from a minimum calorie requirement standpoint. I watched a lean muscular YouTuber prepare his one meal which was mostly cauliflower mash and totaled 600 calories, in which case I call BS since he probably needs about 3500cal/day given his size.

For those of us that aren't burning off excess fat and are active what would a 2700-ish calorie meal look like. Can you learn to eat 2 lbs of steak in one sitting for example and do that every day ? Because it is unlikely there is room in a typical stomach for 20lbs of cauliflower mash or 4.5lbs of pasta eaten all at once.

Also from a time management standpoint spiking your serotonin levels with that massive meal seems counterproductive. Are you really saving time if you are a drowsy for an hour or two after that massive meal ? I realize the parent poster was just contemplating, but if someone has actual experience I would be grateful for a helpful link or comment.

Presumably most people doing it have losing weight as a goal, not maintaining?

Anyway, fat heavy foods make cramming calories pretty easy. You can hide a lot of butter in mashed potatoes or a pasta sauce.

It is the best I have felt in some time in fact.

The body gets used to it over time. I am not strict with it but most days I find it easy to do.

Lots of water throughout the day helps with the empty stomach and not feeling dehydrated.

I skip breakfast and lunch. But can eat heavily within my time window.

The science is off here from my experience.

The metric to watch is time between meals. If you can go 16-20 hours before your next meal, sleep can be included, then you will find your gains staggering.

I think he is saying you can have ice cream or pizza or whatever. Just not right now. So you get the benefits of calorie deficit now and can satisfy the craving later

>Common wisdom says that the body goes in hunger mode if you restrict calories.

Is it common wisdom though? As far as I know common wisdom says that if you restrict calories then the blood sugar drops and that cause the body to go into hunger mode. The difference being that you can eat, say, 1000 calories of your normal diet and go into hunger mode or you can eat a diet that causes the blood sugar to be stable and not go into hunger mode. This is one of the two main reasons LCHF work so well (the other being that you are way less hungry after 1000 calories of a high fat diet than after 1000 calories of high sugar).

I'm very skeptical of the claims about Insulin being a cause of weight gain or preventing weight loss.

All insulin is, is a signal to cells to absorb sugar from the blood. Think of it this way: if you consume dietery fat, your body will obviously not ignore this fat in your blood and start pulling fat out of your fat storage. It will wait for the fat flowing through your blood to be all used up first. Why would sugar be any different? You have to believe that the design of the calorie input management system is so broken that it reacts so badly to carbs but doesn't react in any negative way to fats.

There's another "theory" of diebetes too: that excess fat int he cells blocks insulin reception. So if you consume high fat, you better not consume any carbs with it or else your body won't know what to do with it.

Now, think about it from an evolutionary point of view. Our ancestors have been sustaining themselves on farming carbs for thousands of years (potato, rice, grains, etc). We should all be very well adapted to a diet that is a mix of carbs and fats and proteins. What is different in the modern age is not an excess of carbs; it's the lack of movement. Athletic people consume upwards of 3000 calories per day with no problems.

I totally agree. Since I started IF, my gut seems healthier which is probably interconnected with how I process energy.

> You don’t have to abstain from anything.

I mean, you _do_ abstain from eating. But I always found it easier to abstain from something entirely rather than to do it in moderation.

> But I always found it easier to abstain from something entirely rather than to do it in moderation.

Not a knock or being troll-y but that sound like a religion. As in, funny how patterns established in religion are just as effective outside that context.

I hope I am not oversharing but I definitely need my patterns to cope, I have ADHD so perhaps it is related to that. Maybe something along the lines of lessening the impact my poor impulse control has on my life by avoiding situations in which I could act impulsively. For example, I do not buy sweets and pretty much never have any at home because ignoring them in the store is easier than ignoring them at home. For me, it is an Herculean task to start a bag of sweets _without_ also finishing it in one sitting… but buying no sweets in the store? That is easy peasy lemon squeezy.

Ok I am not a philosopher but is it really “abstinence” if you only have to wait 8 hours?

For a lot of people, waiting 8 hours to eat is a long time. If you’ve ever been around snackers, you know what I mean.

Yeah but this can extremely plastic. Snacking is something you do, not who you are :)

I ate 5 or 6 times a day for 15-20 years. I would eat 3 meals, a snack in the afternoon, and then something before bed. And probably more than that to be honest. I was as much of a snacker as anybody.

In April I switched to eating 2 meals a day. I was very hungry for literally 1 or 2 days, and then I just got used to it, and started to like it!

Before that I was on a pretty strict diet for ~4 years. But I relaxed the diet after changing the schedule, and lost about 5 lbs. So the heuristic of just eating twice a day turns out to be easier to maintain than a diet.

Go figure! It was kinda shocking. I do think "3 meals a day" is a relatively recent thing. Millions of people lived for thousands of years without eating 3 meals a day.

Some downsides: I eat bigger meals, and I notice a bigger "tired" crash after dinner. But I think that's better than feely slightly groggy multiple times a day. I definitely am more aware of the fact that eating "slows you down". I do think there is something to the "alert, fasted" state, and I would call that pleasant.

Also I might have slowly gained back the 5 pounds but I'm still under my target weight ("normal" BMI which is like 20th percentile). I think after 6 months your body probably gets used to it, and maybe I relaxed the diet a bit too much. I'll continue to tweak it in the future.

An upside not to be discounted is that I spend less time and money on food, and traveling is a lot easier as a result!

Reminds me of the joke about celibacy. Most people are celibate 99.99% of their total hours lived. But if you intentionally add 0.01% to that, people lose their mind.

Just for fun I did the math. An 80 year lifespan is 700,800 hours. 0.01% of that is only 70 hours. I think most people have sex for more than 70 hours in the course of a life time!

The point still stands though.

Differences in efficiency.

I think with IF it exploits the fact that your stomach can only take so much food at a time. If you restrict your eating to a small window, you can't eat a whole day of calories in that window just because your stomach can't take that much food. It's like exploiting the fact that your stomach is a buffer and you fill it only at certain times of the day.

IME, most people find it rather easy to take in a days worth of calories in a single sitting, with the right (wrong?) kinds of food.

Like... a largish portion of very cheesy mac 'n' cheese will do it.

> cravings are real, abstinence doesn’t work, and there are always new foods and new temptations

If IF worked for you that's great, but you shouldn't imply every other diet doesn't work. In my case all I did was track calories of everything I ate (Lose It app, highly recommended) while maintaining a normal eating schedule. Down 105lbs so far. For me I feel like if I just ate whatever I wanted in specific timeframes it'd still be too easy to eat 3000-4000 calories.

I was like that too but eventually after doing one meal a day Ive been feeling full on anywhere from 1200-2200 calories. Really depends on the food where I'm at and what's around. But you're absolutely right, there's not one BEST method for everyone. I personally cannot stand the minutiae of calorie counting and measuring portions so it's not good for me. I will measure portions to learn to eyeball things but yeah, can't do it every time I put food on a plate.

For me it feels uncomfortable eating something I can't track accurately, like it's going to actually have 5 times the calories I think it would, since that's the story for so much food. Like once I was hungry after a dinner and there was stuffing left, so I had some assuming it was a lighter food, then I looked it up and it's actually extremely calorie dense.

I think what the OP meant is that IF has all the benefits in one, simple to use format.

You do not need any apps, you do not need to count calories and you do not need remove food you love from the menu.

And while it may sound that you would try to overcompensate for not eating during specific timeframes, what happens in reality is that your body responds by wanting less food, not more.

That’s fair, in my head I was singling out food-restrictive options like no-carb fad diets. Navigating this world of abundance with our ancient brains is hard so however you do it, congratulations

I think what the comment you are replying to is saying, and which I agree with after trying IF, is that IF works simply by making it easier to restrict calories for the average person, not that other methods are impossible or can't work.

I mean, just take your example. Counting calories for everything you eat is a significant amount of work, and it's really easy to cheat if you're feeling hungry ("Oh, look, my app says that an 'average' blueberry muffin is only 250 cals, so that's what I'll put in, despite this muffin being the size of my head").

With IF, all you have to think about is whether you're in your feeding window. You can still cheat, but there is no ambiguity about it, so for many people (or, fine, at least for me) it's easier to keep with it. I found myself getting super hungry during my fasting period, but I knew I just had to wait until my feeding period, and I actually found it difficult to overeat during my feeding period because I would just eat until I was full and then would "run out of time" to overeat.

It doesn't feel like work to me after I'm used to it, just a part of life. I'd only be cheating myself if I cheated on it, so I always err on overestimating.

I also track protein to make sure I get at least 170g, so that's an additional benefit.

170g of protein?? Are you also doing a carnivore diet or keto?

"gram of protein per pound of bodyweight" is a fairly standard macro ratio in the fitness community.

170g of protein is only 680 cals, so plenty of room left over for carbs and fat.

Right, and in my case I was only going for .8 grams per pound. It's hard to do without going over on calories without a lot of meals being skinless chicken breast.

I think the formula is .8g per kg of bodyweight, not per pound. That’s a significant difference.

That's for the average person, but for someone who's trying to gain muscle, a minimum of .8 per lb is recommended.

I agree with your sentiment but would add I think counting calories is a better strategy than most people think. For many they lack a very high level idea of how many calories they are eating, particularly for sugary drinks. By learning to ballpark better I’ve seen people have success. And for that it’s only tricky for a couple weeks, then you just get good at estimating and it becomes more automatic. Ultimately whatever works is best but I wish more people would give counting an honest shot, especially after seeing how well a few folks I know did once they started doing jt.

Agreeing.

I personally find it psychologically much easier to not eat at all for now (knowing I'll feast in a while) than to exert the effort of eating less when I'm eating now.

Last time I IFed I found hunger to become a more varied signal and something much more under conscious control.

Some hungers turn out not to be that urgent.

There's a different hunger for an empty stomach and for a suddenly drop in blood sugar, etc.

I mean different body signals tell you that you are hungry and you learn to introspect them a bit.

I had quite a bit of fun trying to get to biochemical/physiological/phycological understanding of the triggers/sensations.

The one I could never quite crack is a craving to chew when I could tell my stomach was full and I was satiated otherwise.

> Lose It app, highly recommended

It has become such an annoying nag though. If they offered a reasonable one-time payment -- not even for premium features, just to make it stop nagging -- I'd pay it. But no, they want me to subscribe. No thanks.

my folks lost a ton of weight using Noom. I'd try that if Lose It annoys you.

I'll take a look at that. I have occasionally considered writing my own simple logger that fit my needs (I don't need a really fancy database of nutrients, my diet is somewhat repetitive, so the basic FDA stuff would be fine) and then releasing it for free. That's a lot more work than just paying Lose It, but I really don't care much for software subscriptions for every little app.

I used to use lose it but swapped to fat secret. Its database isn't as good as lose it but it's getting better and it doesn't nag. I found Noom infuriatingly naggy and when I went to cancel there were multiple guilt trip prompts I had to OK through before they would cancel my free trial which turned me 100% against them.

I have same reaction to payment plans. I fully understand the business goal of recurring revenue, but several times in last few months I’ve opted for workarounds/alternates rather than paying a subscription for a product where I would have just paid a flat fee if available.

Temptation is managed by just having a little patience until your next meal.

My hypothesis is this is the key.

I do something similar to IF. I’ll eat two meals before 10am then won’t eat until 7pm or so.

It’s not that I don’t get hungry it’s that I kind of don’t care? It’s not a big deal and I can wait until the next meal.

Overcoming the psychological “need” to eat is a big part of it.

I like this approach. My understanding of my metabolism (and I suspect most others') is that if I eat a fair amount all morning, my body is fueled up and can therefore spend energy without worry of conservation to survive starvation.

If I skip breakfast, my body and especially my mind seem slower and weaker for the entire day. I feel like I have to drag myself through the day rather than be pushed. And, when I do get hungry later in the day it's very difficult to ignore. I suspect this is because my body is worried about food.

Is metabolic economics a thing?

There is unexplained difference regarding body energy usage if one eats most calories before noon or in the evening. With the former body spends like 100-200 more calories than with the latter. This is independent of sleeping patterns, what one eats and what one is doing. Even if one works night shifts, the same pattern persists. And it is not clear where exactly the extra energy is spent.

Wait, so about that night shift.. you mean “before noon” isn’t a relative reference to a period of time after waking, it’s an absolute reference to time of day regardless of when sleep takes place? That’s interesting.. irrespective of latitude (sunlight hours)?

Yes, this is in reference to absolute time as measured by highest point of Sun. The effect is so puzzling that there were plans to see if it exists in polar regions during winter time the last time I read about it.

I do the opposite. I do not eat breakfast and I'm completely fine. Dinner is around 6 p.m. so I go about 18 hours without food every day.

I only have coffee in the morning and the only calories in that come from a bit of milk I take in it.

I don't necessarily feel hungry at lunch time either. If there's something going on at work (prod issue, in the zone) I might find myself at 2 p.m. without having eaten.

Sometimes on the weekends I will have a leftover pancake w/ jam for breakfast. What I noticed is that if I've had that, I usually crave food again at noon.

If I've fasted since an early evening meal and I skip breakfast (and I've done it for a week or two) I'm razor sharp until I eat.

My mind feels significantly keener.

In fact I used to dread eating something, anticipating what felt like a loss of 15 IQ points

What meal do you skip? My problem is that I can’t skip breakfast or I get lightheaded (I’ve passed out working out before breakfast multiple times). And I feel like during the work day I need glucose for my brain to function.

If you're gonna work out early in the AM it does make sense to have some kind of fruit or light snack right before. Or you can drink BCAAs during the workout to keep you energized. Just don't let that turn into eating a proper breakfast at like 6am otherwise you're going to end up eating an extra 500+ calories a day.

I find breakfast the easiest meal to skip, and putting sleep in there and skipping late nate snacks makes a 16 hr fast fairly easy.

My wife is like you though, so obviously it depends on the person.

I had the same problem, but it gets easier if you train it.

I recently started cycling for 1h in the morning without having breakfast, and after a few days it became quite easy. Just don't try to convince yourself that it is somehow a bad thing to skip breakfast. Breakfast only makes you hungry for the rest of the day.

I'm doing 16h/8h intermittent fasting, and I only feel slightly hungry on some days in the last 1h before my feeding window.

I skip breakfast aside from one cup of unsweetened coffee and on the other end I brush my teeth for the night with my daughter when she goes to bed at 8pm.

At some point your body starts making modest amounts of ketones overnight/until you eat, so you can still be productive without eating.

The problem I noticed with IF or other "diets" which don't track calories in some way, is that people may tend to eat a lot more once they start doing physical activity, negating the weight loss benefit or gaining too much fat.

The method I recommend nowadays is to keep your diet as constant as possible, then replace meals or snacks with protein rich, lower calories alternatives until you're satisfied with your protein intake (depending on your weight) and you hit a maintenance diet and , as in your weight doesn't change averaged over two weeks, while doing your normal training regimen (which should include some incremental resistance training for muscle gaining or preservation and some cardio for heart health).

Then you have the choice of adding a 200 calories protein rich snack if you're trying to build muscle, removing a snack for 200 calories (if you can manage that) or adding some daily cardio consuming an extra 200 calories (like a 20m cardio class, 2x20 minutes walk, a martial arts class, gymnastic skill-work). You should always weight your self to keep track of things. Eventually you'll weight will stabilise to a new low or a new high and you can go through the process again.

In this way, you don't really count calories, you just roughly know that you'll have a few eggs for breakfast, some pasta for lunch, meat or fish for dinner.

I agree with everything you wrote, and kudos for finding something that works for you.

I'll point out that IF didn't work for me, at least after an initial small drop of bodyweight (2-3kg IIRC). As you said, the reason IF works is the same reason any diet works - it helps restrict calories. But in my case, there were a few problems:

1. I was soon adjusting to the "eating window" and was eating extra portions, cramming in dessert before the window closed, etc. This meant I wasn't eating less calories.

2. I found it very inconvenient to stick to - family dinners, going out to nice restaurants for celebrations, etc caused issues.

A different approach worked much better for me, namely tracking calories using MyFitnessPal, and learning to eat more satiating foods (low calorie density foods as some call them). And especially "anabolic" recipes as they are known around YouTube (basically, low calorie high protein foods).

This gave me way more flexibility, for one thing, but also a much better understanding of how food and energy work - what kind of substitutions are "free" from a food-enjoyment perspective, but super helpful to lose weight.

But like you said - whatever diet is sustainable for you and causes you to eat less calories is a diet that will work.

Didn’t work in my case. I could fast 16 - 18 hours a day without difficulty. But I made up for it in what I ate in the remaining. Always felt hungry and ate more than I should when not fasting. Still gained weight. Tried IF for months without losing weight, and actually gained a little.

Same. I toughed it out for almost 6 months because your body is supposed to adjust but mine never did. I was doing 12-8 and some days I was so hungry I would start getting blurry vision by 11am. Didn't lose an ounce either.

It’s fascinating how different peoples’ bodies are. Maybe try a slight variation? My father in law has been restricting his food intake to 600 calories per day a few days a week for years, and it’s done wonders for him. The exact numbers might not matter; 700 calories twice a week may be better for you, for example. I’m just thinking this might be good for you if you need some constant (but low) calorie intake.

36 hours was the key for me because you can’t make up for that the next day (eat at night and then nothing the next day until the following morning). If I stick to that once a week, I am good. Otherwise, not.

> abstinence doesn’t work

Well, it does. I don't like to feed the myth believed by overweight people that they won't lose weight if they simply started eating 2000 kCal/day. It's psychologically hard, sure (for some) but it would work.

However, it's often easier to eat "nothing" than a little -- especially of high-carb products. It's easier to eat no tortilla chips than to have "just one".

And getting used to a np-food period of the day similarly helps to stop the cravings.

People have been banging that drum for decades, meanwhile the developed world is becoming increasingly obese. It's quite clear that telling people they should just eat less doesn't work.

Thanks for sharing. Does that mean if I do IF I can still consume the same calories I consume right now, just in a shorter period?

BTW what does your IF plan look like? I'm thinking about between 4pm (needs a coffee around 2 or 3) and 8am but not sure if it actually is IF.

The idea is you can eat whatever, but when you come to it there's a natural limit for most people then you feel full and don't want to eat more.

If you imagine it to extremes, if you put all your food for the day on a plate and gave yourself 1 hour how much could you eat if you weren't trying to make yourself sick?

For most people of you only eat between noon-8pm, say (”18-6”) then you'll reduce your calorie intake naturally. Couple it with appropriate exercise and you'll lose weight (doesn't mean you'll be healthier necessarily though!).

> I'm thinking about between 4pm (needs a coffee around 2 or 3) and 8am

This is (called 16-8, 16hr fast and 8hr eating window) is actually a recommended way to start IF. I've been on it for ~4 months and can second the effectiveness of weight loss.

About the calorie intake; a funny side effect is that I'm now naturally less hungry even during the 8hr window so the calorie intake has automatically reduced.

I was wondering why would that be and then learned about insulin resistance and things began to fall in place.

Now I'm doing 16-8 IF and close to zero added sugar diet (which is painfully difficult in Indian cuisine, more so during this festival season :-|).

I’ve lost 20 lbs on IF and this is spot on. It’s just a lot easier (for me) to eat way less. I just only eat after 5pm every day. Much much less for me to think about vs any other diet. Its tough at first but mind and body adapted after a few weeks.

Your intuition is pretty close to the science: https://www.youtube.com/watch?v=BaDmSEVPZiM

You still have to abide by Calories In, Calories Out though. If you're eating 3000+ kcals but doing IF, you're still going to gain weight.

I've been meaning to get into IF forever. Do you mind sharing what system/method in particular has worked for you?

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