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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.

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.

> 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.

> 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.

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.

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.
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.
> 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.

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.

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?
That...isn't what the study says, I think. In fact, it says that the level of hsCRP--a marker of inflammation--actually increased in the subjects who undertook intermittent fasting, though the difference from the control group (1.02 ± 2.73 vs. −0.25 ± 5.66) was far from statistically significant (p = 0.23, see Table 3). That's the only part of the study that even mentions inflammation.
Can somebody comment the effects size of improvements

HOMA-IR (−0.75 ± 0.79 vs. −0.10 ± 1.06; P = 0.004) and

MSS (−0.34 ± 4.72 vs. 0.31 ± 1.98, P = 0.006).

Without knowing the normal range it's impossible to say how big change 0.75 (HOMA-IR) or -0.34 (MSS) are. The article says significant, but how much that is.

Also worth noting that the sample (as a whole) was 96% white, 91% non-Hispanic, and 33% male.

Granted, the study was performed in SLC, but these numbers suggest that this is not even a particularly representative sample of SLC, much less of the nation as a whole.

Also, this isn't IF as popularly understood. IF usually means uninterrupted water-only fast for a certain part of the day, e.g. 18:00-10:00.

The paper is about "low frequency" IF, which in this case means a 24h water only fast, twice a week for a full month, then only once a week for the rest of the trial.

Odd title. Study doesn't mention any anti-inflammatory response. The change in hsCRP in Table 3 actually seems to show a (non-significant) pro-inflammatory measure.
I came here to say the same thing. The improvements are to insulin resistance and metabolism. Are those factors well-known to be related to inflammation?
It was a very weird transition, as a well-off American, from going to never, ever actually feeling _real hunger_ at any point in any of my normal days (our workplaces, transit hubs, homes, lifestyles, and app landscape are all designed to deliver/provide high caloric density food, in extreme abundance, at all times and places, from snacks to full meals), to regularly/often being actually hungry for some/all of most days.

It's done wonders for my well-being - anecdotally, of course.

It turns out we don't actually need to never be hungry; our society just pushes us to assume that even the tiniest pang of hunger is a negative health issue that is to be instantly eradicated. It's actually fine as long as you're not skinny or otherwise malnourished.

It's ok to fast, and to hear your body demanding sustenance and just say "no, maybe tomorrow" - doubly so if you're 10kg+ overweight like I have been (in my case, 20-40kg) my entire adult life.

> society just pushes us to assume that even the tiniest pang of hunger is a negative health issue

This is the mistake. In fact, the hunger pangs and light headedness, nausea, etc. are the result of low blood sugar. This can be a dangerous condition, but our body is equipped to deal with that situation - it can create sufficient energy from stored energy (fat and glycogen) - and will do so if we let it. But most people have conditioned their bodies for a steady supply of easy energy, and this makes the body increasingly less willing to go to the stores for energy (we are at a hormonal imbalance with excessive insulin prevalence which works to lock up fat stores and crave quick increases in blood sugar).

This condition can be gradually fixed with intermittent fasting, which gives the body time to burn off the blood sugar spike, and concomitant insulin, and allow the process of fat burning to pick up, before you start feeding again.

The effect of the fasting can be enhanced by eating fewer carbohydrates (which are the main trigger for blood sugar and insulin), which is the principle behind the keto diet.

> It turns out we don't actually need to never be hungry; our society just pushes us to assume that even the tiniest pang of hunger is a negative health issue that is to be instantly eradicated.

Huh, is that really something you feel like your society teaches you? In my upbringing (UK), snacking was very much discouraged (you won't eat your dinner) and although eating meals was encouraged, going without one was never seen as a health issue and would be seen as preferable to giving me other food if I didn't like what had been cooked for me.

You may be onto something here. I never thought about this effect of IF. The self-control aspect of overcoming hunger, or not just eating when you needn't to.
How do you deal with distracting hunger? I try ignoring it and then find myself subconciously going to the fridge every 10 minutes. And I'm not doing somewhat abnormal things like not eating for 20+ hours.
I am a big IF fan. Specifically, I try to do it 3-4x a week. I skip dinner and start at 5pm and hold it until 9am. I tried skipping breakfast before, that didn’t work well for me.

Two things have been difficult for me lately:

A) sudden extreme cravings before I start at 5pm

B) a sore throat starting at around 9-10pm. I have no clue why it happens.

Do you guys experience something similar and how do you deal with it?

EDIT: Sorry for the confusion. I meant heartburn.

I've been doing time-restricted eating for maybe 5 years, only eating between 12 and 7-ish. It's not what this experiment studied but is supposed to have similar effects. One thing I can say is you get used to it quickly and no longer feel hunger in the same urgent way as before. Hunger is more of a vague "yeah, I could eat now" feeling in the back of the mind, which can be easily ignored for several hours. Mood never changes, either.

On the few occasions I've gone 24 hours+, the hunger feeling is a little stronger, but still pretty easy to ignore. For one example, there is no difficulty going to sleep.

None of this applies when you are first starting out though :-)

I’ve long considered my Sunday runs (26km usually) as a form of sped up intermittent fasting. There’s something fascinating about burning a day’s worth of calories in 2 hours.

Took a few years of practice to get my metabolism to the point where it can burn ~2000 calories in 2 hours and munge through enough food to feel fully operational the same day. I wonder if the overall effects are similar to intermittent fasting.

Anecdotally I’ve noticed that training for long distance running has made me a lot less sensitive to energy-from-food fluctuations. If you can run for 2+ hours while eating 100cal of running gels, what’s a little missed lunch while sitting at a desk?

For those who are upbeat about IF: some simple questions:

1. Does coffee/tea count as a "meal"? I can't get through the day without a couple of cups of coffee and tea.

2. This study mentioned a 24-hour water-only fast, not the IF that most commenters are talking about in this post. Thoughts on that?

3. I've been thinking of going on the "Phil Mickelson" diet: https://golf.com/instruction/fitness/phil-mickelson-age-defy... Any thoughts on that?

For a personal anecdote, IF was the most impactful change I did nutrition wise, and I am currently midway testing diets from carnivore to vegan.
Wondering if anyone is in a situation similar to mine (probably not but it's worth a try):

Earlier this year I developed about 30 food allergies (IgE-mediated; I'm using the term "allergy" accurately, not in the fuzzy way we colloquially use it to refer to intolerances, etc, which are entirely different, mechanism- and prognosis-wise). This has absolutely decimated my ability to eat out at restaurants (I literally can't eat anything I don't prepare myself). Logistically it just sucks. It'll be evening after work and someone on the other side of town says "come hang out." I'd love to, but I'll have to drive home one direction, eat, then drive twice as far the other direction. With traffic it'll be 9pm before I can leave, so...yeah, not happening. It's destroyed my social life. My allergies have also affected things that are "quick" or "travel" foods, so basically I always need to heat stuff up. God it sucks.

Naturally, I've arrived at the thought of training myself to "officially" work IF into my life. Unofficially, I do it all the time by way of just...having to go somewhere unexpectedly or staying somewhere longer than I thought, and I don't have any food. About 50% of the time I feel fine and can power through, the other 50% I feel faint and hangry. Can't figure out why.

The other side of this coin, though, is that I'm trying to build muscle mass. Nuff said.

Anyone find a way to satisfy all these competing interests successfully?

Ooh, interesting. This particular study is with full-day fasts 1-2 times per week. I see that insulin resistance improvement was also seen with eTRF (early time-restricted feeding, where one doesn't eat after, say, 2 pm). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627766/
The worst thing I ever did was start eating breakfast. Turns out I was doing IF for over 20 years, because only after I started eating (even a healthy) breakfast did I start to gain weight.
This study seems a little weird (crap) in that they started with a hardcore twice a week fast for a month then dialed it back to once a week. Unless I missed it, I don't see an explanation of why this approach was taken in the paper.

Given the subjects were high cholesterol and/or diabetic, it makes me think their life styles sucked already. I couldn't imagine living like then suddenly being told to stop eating for entire days. I would not be shocked if people didn't really adhere to the guidelines. It seems a food diary was the only thing keeping them "honest". Also a staggering 40% of all participants refused to answer how much alcohol they consumed on average.

If you are going crazy with food or lack of exercise for 6 out of 7 days, I don't think taking a break for one day a week is going to make much of a difference.

I accidentally started IF after being annoyed at my lack of mental alertness after lunch and breakfast.

I found that one coffee for breakfast, lots of water/herbal tea throughout the day, and then eating a huge dinner and whatever I want between 5-9 works for me. It seems I can consume over 2k calories in those 4 hours.

IF is great. IF + low(ish) carb is even better. IF + low(ish) carb + eating calorie amounts matching your healthy weight is amazing.

There is more than one way to lose weight just like there is for gaining weight. Minimize as many of the offending behaviors as possible. Consistency is key. Don't pick something you cannot consistently repeat unless that limited time run is all you're after.

Of the different IF schedules people pick -OMAD, 20:4, 16:8, 5:2, etc-, start with anything that you can do initially without getting frustrated and giving up. You will be able to increase the fasting window over time. It just really works.

Don't get discouraged by words from people that tried and failed (or gave up too quickly), or not even tried but talk out of prejudice. Listen to the encouragement from so many that successfully do it.

Best of luck!!

I'm a big fan of Intermittent Feasting.

Joking aside, I've tried intermittent fasting and had more balance / homeostasis as a result. They say `the first element of discipline starts with your diet`. Control diet, and you control many other things.

If you want to have an "anti-inflammatory" response, then try to maximize your fiber intake from a wide variety of plants.

This will increase the quality of your microbiome -- which in turn, will produce substances that are anti-inflammatory.

So does nutritional ketosis... which is probably why this result was found... because when you fast, you go into slight keto

if you don't like CR or fasting (or being hungry), consider keto as an alternative, just realize that you'll have to do your homework

I've definitely seen the same anti-inflammatory results that this has.

https://www.youtube.com/watch?v=1IEuhp8RFMU

I accidentally did intermittent fasting as a teenager for years. I just didn't have breakfast, had lunch and dinner and oddly enough it matched the requirements to be considered IF.

One day I got interested in IF, looked up the rules and found out I was already on it.

I can't say whether it did anything but it definitely made it hard to consume enough calories, so despite training a lot and despite eating a lot at lunch and dinner, I've always been skinny.

I assume IF could be a good choice for someone who's overweight and barely training or not training at all.

I was training bodyweight and gymnastic at the time, making significant progress in terms of strength - despite that, I saw very little muscle building. I suppose being that lean lowered my testosterone production resulting in little gains.

I had the brilliant idea of even trying going vegetarian, vegan for a while, shifting to a source of proteins which is not as complete and not as well absorbed as proteins coming from animal sources.

After 20 years of reading on the subject and looking at what studies are saying nowadays, if I could go back through my teenage years I would eat close to paleo, 6 times per day and lift weights.

Colitis - I haven't read the article but will soon. But here is a data point for anyone with Colitis, if it helps.

I started IF in July as a means to lose a bit of lockdown weight.

No breakfast, no lunch, only a substantial dinner. 4-5 Drinks taken throughout the day. No real restriction. Lots of walking to keep busy.

I've noticed a significant improvement in management of Colitis. No flares. Enabling me to get back to normal life without worrying about the condition throughout the day. Just (sorry TMI), emptying bowels first thing in the morning (2-3) times. Then don't have to worry all day.

Considering colitis is a primarily inflammatory response (I believe), then this article rings true. YMMV

Once I reach target weight, not sure what I'll do. Maybe just add some more protein or good fats to evening meal. It's been too helpful to give up the routine.

It seemed to have helped my epilepsy. It’s mentioned in the bible as a treatment for the disease, and diet based treatments are experiencing a resurgence in use. Keto is sometimes prescribed in kids with difficult cases, and low GI (the south beach diet) is similarly being prescribed to adults since keto is too difficult for most. I haven’t heard of IF being prescribed but my doctor said it may be effective when I brought it up.

I did low carb/cal AM (1 egg) and didn’t eat til 3 PM. I did this most days of the week. There are other confounding variables so don’t take it as medical advice, since the diet can also exacerbate seizures.

Does that mean a 24h fast but frequent is enough to trigger DNA repair mechanism? My understanding so far was you needed at least a 72h fast.
There’s also a 500% spike in HGH after 48h according to Dr Ekberg
Ferritin is a marker of inflammation of the liver and anecdotally it rises when fasting.
The cult of IF among tech nerds is one of those bizarre subcultures I'll never get used to. Here we are, modern human beings who live twice as long as their forebears, and yet a small fraction of them feel they need to regularly and intentionally starve themselves in order to be healthy. Humans are goddamn weird.