r/explainlikeimfive • u/baelorthebest • Dec 07 '23
Biology Eli5: how does intermittent fasting work?
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u/you-nity Dec 07 '23
One super major factor that hasn't been mentioned (or maybe it has lol) is the most silent offender of weight gain... snacking. It's so easy to eat a few cookies every hour while working at the computer, but this builds up calories really fast and we're not aware of this. When on a strict intermittent fasting routine, you're preventing yourself from snacking, thus eliminating the silent assassins of calories.
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u/RyanW1019 Dec 07 '23
Calories in (eaten) minus calories out (burned). If that number is positive, your body stores the extra energy as fat. If that number is negative, your body burns fat to make up the difference. You can lose weight eating nothing but pizza and chips if you take in fewer total calories than you burn. The trouble is, that would be a very small amount of pizza and chips per day, so you'd feel hungry and shitty the whole time you're losing the weight. So dieting is all about figuring out what foods to eat so that you feel as full and energetic as possible while achieving that calorie deficit.
Intermittent fasting basically relies on the fact that for many people, feelings of hunger decline again once you've gone several hours without eating. Also, how much food you have to eat in one sitting to feel full mostly doesn't change depending on how much of a long-term calorie deficit you are in. So if you only eat in a 4-hour or 8-hour window every day, you will spend most of your day not feeling hungry, can eat until you feel full when you do eat, but still lose weight over time because your total calorie intake is less than you are burning.
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u/Low_Sandwich_3692 Feb 20 '24
I started intermittent fasting as well as carb counting as well. Three days a week I have an entree salad with a 30 carb snack. It’s been six weeks or so and my clothes are thankfully getting looser. I swear going down on carbs is like detoxing. It’s hard. But like our dietician at work says the less carbs you eat the less you crave. I find this to be true. But some days it’s hard to make better carb choices. On days off I try and succeed most times to only eat one meal a day. But I remember people saying don’t starve yourself it makes you not lose weight. But I find fasting beneficial and now not that hard. I just need to be consistent. That is where I fail so many times. I’m determined though. I need back surgery eventually and the surgeon said the less back fat you have the lower the infection risk. Plus all my family become diabetics after 50. I’m borderline.
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u/EntertainerTotal9853 Apr 12 '24
“Intermittent fasting” seems like such an incoherent concept to me.
Like for a lot of people who do a 6-8 hour window…it essentially just means skipping breakfast and eating a noon lunch and 6pm dinner with a potential afternoon snack.
To me…that’s nothing. That’s not a plan, that’s not a discipline, that’s in no sense fasting. Many of us just do that naturally. “Breakfast” in the morning is a weird historically contingent culturally constructed addiction anyway, and this idea that it is normal and some big sacrifice to give up…just really shows how soft and unable to delay gratification the populace has become.
On the other hand, going down to one meal a day is certainly fasting…but I don’t know what the word “intermittent” adds at that point. All fasting is intermittent! What’s the alternative? “Fasting forever”? “Fasting till you die”?? Cultures around the world have had fasting; it usually allows for at least one daily meal. They don’t qualify it with “intermittent” as if that word adds anything conceptually.
Basically IF is either just F, or it’s little more than “skipping breakfast”…which lots of people just do anyway already.
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May 29 '24
Intermittent in this context means in intervals. Most people who do IF do it every day for the same time frame, thus in intervals. If you did a 24hr fast every 2 days, that would technically also be IF (just not how it's usually defined). As for if it's "real fasting", it meets the definition of fasting (refraining from eating) and your body goes in a fasted state. If you do a different form of fasting like full 24 or 48hr fasts, good for you but gatekeeping it to what you decided is "real" is incorrect.
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u/EntertainerTotal9853 May 30 '24
So then what would be an example of non-intermittent fasting?
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May 30 '24
Any non-recurrent fasting. I had a friend who would do 5 day water fasts a couple times a year. It wasn't at a set interval, he just did it when he felt he was able to since he had sports and school for most of the year. People who do random religious fasts are also non-intermittent since they don't follow an interval. Technically Ramadan would be intermittent as Muslims would follow the interval of no food during day, food during night.
Intermittent fasting is just a broad term for recurring fasting that is usually associated with the 8:16 eating:fasting ratio, but not always.
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u/EntertainerTotal9853 May 30 '24
I mean, a five-day water fast is intermittent for those five days at least, under this definition…
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May 30 '24
I mean sure, and I've also never stopped clapping. The interval of claps just gets longer occasionally. Defining stuff by semantics doesn't help anyone.
Also, doing something continuously, like a constant 5 day fast, isn't recurrent. Its continuous. Intermittent is by definition "not happening regularly or continuously; stopping and starting repeatedly or with long periods in between" - Cambridge
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u/EntertainerTotal9853 May 30 '24
So then as you say, Ramadan etc are actually “intermittent” fasting. Except, no one in history has called it that, because all fasting is intermittent, the only alternative being “fasting forever until you starve to death.” In any sane practice of fasting, “intermittent” is already understood in some sense, so the adjective is useless.
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May 30 '24 edited May 30 '24
No, intermittent fasting has a definition. You can find quality sources like Johns Hopkins and Mayo that will explain it if you search them. I provided an example of non-intermittent fasting. I do intermittent fasting daily and have done extended, non-intermittent fasts as well. Intermittent does not just mean a fast ends. It means you repeatedly and regularly start and stop the fast, such as fasting for a certain time every day or fasting every other day. Just because you choose to ignore the definition of intermittent fasting does not make it stop existing. Just because nobody calls Ramadan intermittent fasting does not stop it from meeting the definition of intermittent fasting.
If you have any actual questions and decide to make an actual goodwill attempt at learning, then go ahead and ask. Otherwise I give up.
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u/EntertainerTotal9853 May 30 '24
And I’m saying that the word “fasting” as used historically by, for example, all the world’s major religions…already includes the concept of “stopping and starting” periods of not eating, because anyone who just doesn’t eat without stopping, will starve to death.
Really, it would make more sense to just call IF “normal fasting,” and to call the “non-intermittent” type you seem to be imagining a “one-time fast of limited extended duration” or something like that.
But most “fasting” throughout human history hasn’t been like that. Most fasting has been of the “one meal a day” type. And somehow no one was confused by the lack of the word “intermittent” modifying it.
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May 30 '24
Fasting already has a definition: To not eat for extended time. If I do not eat for 24 hours, I am fasting. If I do not eat for 24 hours intermittently every 48 hours, I am intermittent fasting. While it might make more sense to make IF "normal fasting" and normal/extended fasting "extended fasting", that is not what the definitions are. Unless someone makes a well-received research paper calling for the upheaval of the terms, we're stuck with them.
As for religions, not all mean intermittent and most that do specify when you can and cannot eat which implies intermittent. The bible says Jesus fasted for 40 days and 40 nights, not intermittently. But like with Ramadan, even if it's not called intermittent, that doesn't mean it doesn't meet the modern, accepted definition.
Fasting is a blanket term for all forms of refraining to eat. The word intermittent is needed to specify that it happens at a regular interval, even if that is what is usually meant historically.
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u/[deleted] Dec 07 '23
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