I have zero medical qualifications. But I largely skip dinner these days, and I do feel healthier.
Is it actually doing something different to my body chemistry - doubtful. It's probably just a lower caloric intake combined with hey, I sleep better when I don't have indigestion in the middle of the night from eating something delicious before bed.
There's some woo arguments in favor of it, but it's not completely bs, IMO.
It's basically a way to trick yourself into eating less by restricting the hours of the day you eat. Once you're doing it for a while your body adapts to it and you're much less hungry during your fasting hours.
I lost 60 pounds doing it without much pain. I still fast 12 hours(which is mostly sleeping) to maintain the loss.
I've done this my entire adult life. Not as a diet, I just eat this way. I'm 6'4 and 180 lbs with an athletic/muscular build. So it seems to work for me but I also don't eat garbage food. High fiber, high protein, low fat, low sugar/carbs.
about 9 months ago, i was curious about it and started at a 16:8 with my eating window between 11a and 7p. didn't notice anything, but basically just didn't do breakfast and never ate late. acid reflux stopped. about 6 months ago, i was watching some lecture from a cardiologist give a presentation on autophagy and metabolism and fasting as a healthcare maintenance strategy. it was biology heavy, but delivered in a fairly entertaining way. as a biology nerd who took some human nutrition, animal nutrition, and a whole lot of soil metabolic courses, it was right up my alley. metabolic pathways are complex and us multicellular warm bloods have a lot of adaptability to variable environments, compared to single cells who just sort of go dormant like a robot.
anyway, the lecture made me super curious about a 20:4 (eating window 11am - 3pm). i decided to try that for 1 day. i had this impression that fasting for 20 hours a day would make me all fucked up, cranky, jittery, or whatever. the big change really was confining myself to only tea and water outside of that window, which meant no more artificial sweeteners outside the window. so anyway, nothing weird happened. i was "bored" at dinner time, but decided to just focus on something else. since it went off so easily, i extended the plan to last 3 days. actually had improved energy after that.
i did a week, then 3 weeks. i couldn't see any downsides. it also made me more conscious of my meal time to make sure to eat something balanced, not just some dumb crap to not be hungry. i decided that 2 days a week, i would optionally drop to the 16:8 schedule so i could be sociable at dinner time. i noticed that those extra meal days i was actually sluggish unless the second meal was super small and light. like a few vegetable dumplings or basically an appetizer. even during once a day regular meal, i could no longer pack it away. my capacity for big eating went way down, so i got full very easy and had that "sated" feel.
anyway, im roughly around 6-7 months on it. i have no scale and don't weigh myself. all of my clothes are now kinda loose/big on me. i went in to the doc for my check-in. i've been on 3 different medications for blood pressure, one for cholesterol, and i take stuff with meals for controlling blood sugar / diabetes. that has been going on for literally several years, and generally my numbers have been OK but not great and my meds have only ever gone up. anyway, i dropped 15% of my body weight apparently in the last 6 months. and my lipid panels all came back optimal, my a1c came back as optimal/normal. my cholesterol is ideal. my BP is now too low like a little old lady, so we're reducing my meds slowly and checking back in 3 months. i also feel like i have a ton of energy for shit and i am literally never hungry outside my window. i do get excited at meal time for the novely of eating and have found enjoyment in foods i used to not be excited by. like very spicy/acidic thai dishes that are like 80% vegetables by volume, pickled things. since i'm only eating once a day, i can be very intentional about it and i can spend a little extra dough on it if i want.
i gotta say it's working out for me. there are absolutely people it probably won't work for and some of those people think their situation is universal. they believe those of us having success with it are crazy nutjobs who don't listen to our bodies, so they wipe their asses on our experiences. my primary care physician knows i am doing it and seems neutral about it in general, but very supportive of my results. wouldn't it be crazy if the solution for many of those people succumbing to Metabolic Syndome X was to not force ourselves to metabolize something every 4 hours? like maybe we're some subset of the population that are better adapted to eat less frequently and we shouldn't let others bully us into conforming to their constant snacky snacky yum yum lifestyle because it's literally killing us.
I think one of the things you're striking on here is how IF can be really useful for people who eat excessive quantities and for people who engage in boredom-eating.
By fasting intermittently it sounds like you've changed your relationship to responding to hunger cues, to boredom, to the food you eat, and probably to how big a meal you need.
I think this is why IF is polarising - for some people, such as yourself, it's the right kind of lifestyle intervention and just what they need. For others it doesn't fit well at all. It's a bit like when someone gets a dog or moves to New York and suddenly, 6 months later, they are so much healthier in an effortless sort of way that it seems amazing but it turns out that the change in their lifestyle was enough to tip the scales towards healthier behaviours. Sometimes people just need that external motivation to get out and walk every morning or to sprint to the train, to use the steps on the subway multiple times per day, and to carry their groceries home on foot every other day which is all they needed to achieve a healthier lifestyle.
metabolic pathways are complex
Lol, this is such a mood. As a person who took interest in psychopharmacology later in life, I really wish I paid attention in biology class in school.
they believe those of us having success with it are crazy nutjobs who don’t listen to our bodies,
Some people don't seem to understand that "listen to your body" means that everyone's body is different and different things will work for different people.
I tried intermittent fasting for a couple of weeks when trying out different dieting methods, and I might've given up on it too soon. It sounds far easier to manage than calorie counting, which "worked" but was just exhausting to deal with every day.
Some people don't seem to understand that "listen to your body" means that everyone's body is different and different things will work for different people.
I think it's straight up dangerous to listen to your body under our current material conditions. There are food engineers who are paid extreme amounts of money to hjack the processes filed under what you are listening to. Your entire hormonal feedback loop is subject to attack from a food environment that is mostly ersatz foods - amalgams of sugar, fat and salt which are chemically pre-digested. You consume them so quickly your body is trained from birth to always signal both hunger and appetite.
You gotta listen to your body holistically. Feeling like shit all the time is not normal. Having a bad sleep all the time is not normal either. Check your intake of stimulants and high processed foods. Depending on what you eat you'll feel 5 times better after just a few days on whole or home-processed foods. That also falls under listening to your body, and it's much more pressing in our de-regulated food capitalist dystopias.
what appeals to me is that it is very much a self-directed thing that one can adjust for their own goals and situation. lose weight/insulin sensitivity recovery/cholesterol control/general maintenance has been my main one and the lecture keyed me into what would be recommended, timing wise. if i ever hit some nebulous goal weight and everything on my tests looks perfect and maybe i'm even more active, i would probably try adjusting the time restriction again.
honestly, check out that lecture i linked. it's long and he digresses a little here and there, but he is an amusing lecturer on what is typically a brutal topic. i still remember memorizing functional groups in biology and, as a systems guy, i was like FML.
anyway, he talks about how IF/time restricted feeding gives metabolic processes, especially those related to insulin regulation, a recovery period. and because there's this pause of 16-20 hours, it gives the hormone receptors that have downregulated from the consistent influx / overabundance of insulin a chance to recover a more typical sensitivity. that means, when you do eat again, your pancreas doesn't have to flood you with a high level of insulin to control blood sugar. there's a lot of other stuff going on that insulin cascades into, but when he talks about how much energy it takes for the body to simply convert the food we intake into some energy for later, it was pretty eye instructive as to why we feel run down after eating. and if we are eating frequently, we are staying in that state. digesting food is very energy intensive. we are putting a bunch of foreign matter into us and forcing our body to, as quick as it can, make it safe, break it down physically, chemically, and microbially at various stages to strip it of usable materials to convert into short, medium, and long term energy storage as well as a whole suite of vital nutrients, and keep it moving along the way like a reverse assembly line taking apart a car and creating a pile of whatever it couldn't figure out in time mixed with whatever could be toxic if it stuck around. while also filtering out out water for ourselves. think about how conditioned we are to intake caffeine with / shortly after meals to mentally overcome this massive energetic effort going on inside us.
for me, it's been the most significant lifestyle change i've engaged with where i'm like, "shit this is easy. i could do this forever." i can just eat my meal at a meal time i chose and be full, and then spend the rest of my waking time doing whatever i actually want to do, not worrying about what i'm going to figure out that's healthy and reasonable and satisfying 5 hours from then. my biggest obstacle are family members who have no background whatsoever in biological sciences, are total snacky treat addicts, and have had to resort to major medical intervention (with frightening side effects) to basically not die from their lifestyles. i was the last one in my family to develop syndrome x symptoms, because i was always just more active, worked physical labor jobs for my 20s-30s and have generally been less snacky. but it caught up to me in my 40s. until i found this, i was basically slowly, steadily heading down the same road. and when i started it, they were all like "you're going to die. that's impossible. you have to eat 5 times a day to keep your metabolism up. join us in our constant snacking and treat chasing. you're hurting your body." now that i'm not dead and my doctor is like, "wow, whatever you're doing is working" they aren't sure what to do. they still try to sabotage me by pushing food and snacks at me (with "concern") whenever they want to chase their own dopamine hit. "try this powder, try this supplement, try this diet meal plan subscription." just all the same "common sense" pack of bs that have been pedaled for years to sell shit to unhappy people with all the diseases of modern civilization. the hilarious thing about IF that the lecturer addresses is he gets zero industry support for anything his foundation does, because he's not selling anything. that lecture's audience are other healthcare professionals because he wants to reduce the damage being done by pushing old narratives the science has grown beyond. and there is nothing to sell, so industry turns up its nose. he's literally just telling people to consider eating less frequently, to try--with the knowledge of their physician re: medication and situation--fasting for a day, and there is no money to be made with that. there's no specially formulated macronutrient kibble or water flavoring powder or magic cookbook or subscription meal plan or pharmaceutical to patent.
the really fascinating stuff though is when he gets into the timetable of what the body starts doing after insulin levels have dropped (2 hours, 5 hours 16 hours, 24 hours, 36 hours etc), what typically "off" genes start expressing to keep us rolling, alert, energetic, and mentally capable. the autophagy thing is legit crazy, how it was misunderstood for a long time until recently. he points out that any cellular action leaves behind some trash components over time, weird little proteins and fragments that are just sitting there in cells and as they build up, they mechanistically interfere with normal cellular processes. when autophagy is signaled, it starts a recycling process to cannibalize components from junked up/underperforming cells, which then signal they need to be reconstituted as soon as nutrition is available again. it was assumed this was only a starvation prevention mechanism, but it turns out this is a key recycling/regenerative process for preventing cells from becoming cancerous and has implications for neurodegeneration and immune disorders. and if you're eating every 4-5 hours during waking periods, this process almost never activates. it legitimately only starts around 16 or so hours after food intake has ceased.
anyway, i'm "new" to it and had great results at 6 months in, so i'm obviously excited about it. because my family is unsupportive, i can't really talk to them about it so i took this opportunity to gush. maybe if i have perfect blood work/BP, am physically active, and look 35 when i'm 50, they'll respect my lifestyle choices but i doubt it. guess i'll just have to do it for my own enrichment.
Fad diet.
It works like all weight-loss-diets that in some way it reduces your total caloric intake. If you do that by starving for one day every week or drinking lemon water for lunch every day of the week, it doesn't matter.
As for the claims about authophagy in just a few hours, I'm pretty sure that's bullshit. Like all fad diets it promises to "hack" your biology for extra fat-burning or anti-aging or whatever it is this time.
In the end, the best diet for overall health is 
Here’s a good article comparing a couple different studies: https://skepchick.org/2023/06/study-can-you-fast-your-way-to-good-health-maybe/
TLDR is it’s not conclusive, but you can ask your doctor about trying it out and as long as you don't turn it into an eating disorder and starve yourself, it might be worth seeing how it works.
Solid TLDR for nutritional advice.
I skip breakfast, no negative side effects and that is technically "IF" but as everyone else says your experience will be different.
Minor CW: disordered eating, drugs, animal experimentation.
Seems like a lot of folks have responded while I was away, and my last couple hours of research tends to agree with them. Seems like my initial knee-jerk skepticism might have kicked in a little hard in this case. I'm pretty drained from work so this is probably going to be a half-assed kind of effortpost, but here we go anyway, because getting deep in the weeds about food and diet is kinda what I do.
All other things being equal, being a healthy weight is going to be better for you than not (this goes for over and underweight), regardless of what specific method you use to maintain your energy balance. That is, provided you're not doing anything extreme (e.g. keto, binging / purging, meth). So, in that sense, if you can maintain a healthy weight doing intermittent fasting (IF), it's probably alright. Or at least, not bad.
It gets a bit more hairy when you get into the science. While the RCT quoted in the Skepchick article that someone posted upthread is good, RCTs are necessarily limited in scope. This particular one only compared 8-hour time-restricted eating (TRE) to a calorie restricted diet over 12 months, and for weight loss only. They performed about the same. There are several meta-analyses (aggregate analysis of other RCTs) that generally agree; most forms of IF do about the same as continuous energy restriction (CER -- ie low-calorie) diets in terms of weight, fat and cholesterol over a long enough timeline. However it's worth noting that IF only works if you -actually- reduce calories overall. Fasting does nothing if your weekly calorie intake stays the same (eg- binging on high calorie foods on your "feast" days).
Additionally, there are different forms of IF. This umbrella review of meta-analyses focused on four kinds; Zero-calorie alternate day fasting (ADF) ie- eating only every other day, modified ADF (restricting calorie intake every other day), 5:2 (five days eating, two days fasting at various calorie intake levels), and TRE, as explained above. It does highlight a few places where specific kinds of IF MIGHT outperform CER for certain outcomes (5:2 diet for fasting insulin, for example) or in certain situations (MADF might be better for obesity). But this is really dietician territory, and I'm not a dietician. If you have a specific problem beyond wanting to be a healthy weight, you need to talk to one. Incidentally, this might be where some of the woo around it comes from; there is some preliminary work in animal models and theoretical pathways suggesting it might have some benefit alongside chemotherapy. This is really cutting-edge theoretical stuff, and I'm not an oncologist, either. It's a big deal if it's true, but nobody is sure yet. OTOH, being a healthy weight definitely reduces your risk by a good margin. If fasting is what gets you there, cool. Just don't neglect actual medical treatment if you need it.
Other folks have also mentioned the risk of it evolving into disordered eating. There are survey studies that seem to suggest a correlation, but that's also somewhat true of -any- kind of dieting. This also doesn't really establish causality; ie- are they exhibiting disordered eating because of IF, or are they using IF to mask disordered eating, or is there a common thread where people who tend toward disordered eating anyway might find IF more attractive? Regardless, if you feel like you might be vulnerable to that kind of thing, maybe steer clear for now and talk to your doctor and/or psych about it. I'm not a psych, either, btw.
Lastly, maintanence. There doesn't seem to be a ton of data on this, and what data there is suggests it's about the same as CER. Which is a shame, because generally speaking, losing weight isn't as hard as keeping it off. I imagine it might be easier to integrate a time-based regimen into your lifestyle than a calorie-based one, since you don't have to count anything other than hours. That's kind of speculation on my part, but some of the other anecdotes in-thread make an intuitive kind of sense to me.
Overall, seems like it's probably not much better (or worse) than any other method of calorie control for weight loss. Any health benefits are more likely due to weight loss rather than anything specific about the diet though. Advice about eating disorders is valid, and Your Mileage May Vary. The best diet is the one that works for you.
It’s a real slippery slope into disordered eating for a lot of people. It trains you to ignore your body’s natural hunger cues. I’m glad it works for some people, it’s none of my business how others eat, but it is a fad diet and therefore should be viewed with heavy skepticism.
I also don’t hear this discussed often but social eating is a pretty important part of the human experience, and it sucks when you can’t eat with your friends because you’re fasting.
and it sucks when you can’t eat with your friends because you’re fasting.
its not like i go to parties or eat with my friends every day. and besides its pretty easy to adjust my fast for those days when i do have social calls. instead of eating lunch at midday I eat with my friends at 14:00s.
fasting to me is a perfect means of controlling my anxiety and dealing with the completely out of whack food environment in which we grow up today. the food industry relies on inducing overconsumption. it hjacks our bodies' natural hunger cues via high processed foods. fasting is a natural way to restore a healthy eating instinct. it was only through fasting that i went from wanting to eat all the time to eating in a timely way, valuing each dish i make.
this goes back to eating as a social experience. because i am no longer subject to the deleterious effects of high processed foods i can easily spend a week out with family and friends, eating three times a day, and then return to a reasonable, nutrition based eating period with no problem.
as a side note, the real slippery slope is semaglutide. because those meds are a brute force way to emulate the effects of a healthy hormonal cycle, so it is only logical that once you're off the meds you're back to equating appetite with hunger and feeling hungry all the time.
I’m glad it works for you. Please understand your experience is not universal.
I will repeat: for a lot of people, myself included, IF triggers disordered eating patterns.
Semaglutides are a medical miracle for diabetics who struggle to control their blood glucose
They are also just like all other drugs in that when you stop taking them, they stop working. This is also true of literally every other pharmaceutical, and that doesn’t mean people shouldn’t take their psych meds or their anti-seizure meds or their blood thinners.
I would never try to convince someone to change eating habits that are working well for them, but diets (including IF) can absolutely be harmful for some people and I would suggest being sensitive to that when discussing this topic.
Personal anecdote time I've done it to some success, thing is watching what you eat afterwards. Did it enough times and I noticed I had trouble eating the same amounts I used to eat which I think has helped me more than the fasting itself.
It's reasonable but afaik it's not really significantly better than other equivalent healthy lifestyle changes. I'm avoiding the term "diet" since that carries too much baggage, but you get what I'm driving at.
I think there's additional benefits if you're pre-diabetic as it takes the pressure off your body's capacity to manage your blood glucose levels.
It can be really good for some people, for others it doesn't work any better than other options, and it really doesn't work for some people. If you don't have any major health concerns then there's little harm in trying it but it's not like some massive cheat code where all the work of a healthy lifestyle is addressed by using this one simple trick.
healthy and good for certain bodies, worth doing some research on your own to see if it feels worth trying.
I’ve not found anything that indicates it’s not healthy when done within reason. That is you remain hydrated and have the fat reserve to burn. So fasting doesn’t exclude water. Tea and coffee would be permitted as well as long as no sugar or milk. I also understand the intermittent fasting typically maxes around 72hrs.
Anecdotally, I found it highly effective as part of my dieting routine. I only did the intermittent fasting as a period of “you’re not supposed to eat between these times.” Now if I felt I wanted to break the fast, I made myself spend the effort and make something healthy. I let myself eat if I was actually hungry, but it had to be a real good-for-me meal and something that required dedicated time to make if breaking the fast.
My fasting target was from 8:30pm to 12:00pm the next day. The pattern and habit seems to help control that “boredom hunger”.
I found tracking everything I ate and using a food scale helped me learn what a serving size really is.
I see a lot of keto/low carb hate, but it’s the only one that worked for me. I was able to lose weight and not be hungry all the time.
Do you mean 16:8, 20:4, one-meal-a-day, weekly fasting for 24-48 hours, or something else?
People have been doing a variety of these things for a very long time. There are British nursery rhymes that say "only eat at dinner". Do college dining halls that open for only brunch and dinner on the weekends fall into the category of intermittent fasting?
I've been leaning heavily toward two meals a day for a while for a few reasons. One is that deciding about something to cook every 5 waking hours can get overwhelming. One is that I've been inclined for a long time to be a grazer, and just end up eating all throughout the day, often packaged stuff that's high in simple carbohydrates. I just end up hungry all the time, it keeps my blood sugar spiking and crashing, and it's bad for my dental health. If I eat one big meal with more vegetables, protein, and fat, it means I don't have to keep buzzing back through the kitchen/pantry over the next 6-8 hours. It's also easier to brush and floss after every meal if I don't have this extra meal sometime in the middle of the day when I'm out and about.
I'm not in a position where I can research it at the moment, but I kinda doubt it.
Feels more like a way to make skipping meals trendy.
I'll look it up when I get home from work.
Feels more like a way to make skipping meals trendy.
I don't think so, it might not be for some people but it's not a fad diet like keto.
God I fucking hate Keto
It's so stupid but I'd by lying if I hadnt tried it once because of peer pressure.
Societal beauty expectations go brrrrrr.
I also tried it. Shit was terrible
It definitionally is a fad diet. That doesn’t mean you shouldn’t do it, but it’s important to recognize it for what it is.
What about the millions of people who "just don't eat breakfast"? Are they a fad too?
Skipping breakfast is not the same as having strict windows when you can and can’t eat.
Someone who eats lunch right after noon and dinner before 8 is basically doing the same thing.
"Oops I stopped eating at 9:11 instead of 8:59, my diet plan is fucked" said no one ever.
Fad = not following random vibe takes on hexbear
I started doing it to lose weight. I lost 2lb per week for a period of 10 weeks. Since then I have continued doing it, but much less strictly. I don't eat breakfast and try to have a small lunch (like 2 pieces of toast), then I have a very large dinner at around 6pm. I honestly think I feel much better in the mornings, and I don't get sleepy in the afternoons. The way I started was to slowly push back the time I ate something at the start of the day. At first I didn't eat until mid morning, then after a few days I didn't eat until lunch time, then mid afternoon. After a week or so I was no eating anything until my evening meal.
i do it sort of accidentally, sorta on purpose. combined with my physically intense job i've lost about 35 lbs (of fat) in a 10 mos. still eat lots of calories, protein heavy, to keep my muscle mass up
get up at 5:30 am for work, don't eat anything until about 12pm and it's just a single energy bar (so about 14 hrs?). then eat 2 meals, one when i get home meal and one later. sometimes i'll break it at 12pm with an actual small lunch and eat an earlier dinner
I like it and think it's helpful when paired with a low calorie diet. I drink a lot of coffee in the morning which helps stave off any hunger. Usually I don't eat until 2 or 3 in the afternoon and will stick with a mediterranean style meal for lunch and dinner. After that nothing until the following afternoon. So far I have kept 35 pounds off.
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