Intermittent Fasting: What’s the truth?
Before we get to facts and fictions, let’s quickly cover:
What is Intermittent Fasting?
Intermittent Fasting (IF) is an umbrella term for various kinds of time-restricted fasting, based on a schedule. Types include:
Time-restricted IF, for example:
- 16:8—Fast for 16 hours, eat during an 8-hour window
- 18:6–Fast for 18 hours, eat during a 6-hour window
- 20:4—Fast for 20 hours, eat during a 4-hour window
24hr fasting, including:
- Eat Stop Eat—basically, take a day off from eating once a week
- Alternate Day Fasting—a more extreme version of the above; it is what it sounds like; eat one day, fast the next, repeat
Non-fast fasting, e.g:
- 5:2—Eat normally for 5 days, have a very reduced calorie intake (⅓ of normal intake) for the other 2 days
- Fruit Fasting—have a small amount of fruit on “fast” days, but no other food
- The Warrior Diet—as above, but include a small amount of non-starchy vegetables
Why IF?
While IF is perhaps most commonly undertaken as a means of fat loss or fat management (i.e., keeping fat down when it is already low), others cite different reasons, such as short term cognitive performance or long-term longevity.
But… Does it work?
Here we get into the myth-busting bit!
“IF promotes weight loss”
Mix of True and False. It can! But it also doesn’t have to. If you’re a bodybuilder who downs 4,000 calories in your 4hr eating window, you’re probably not going to lose weight! For such people, this is of course “a feature, not a bug” of IF—especially as it has been found that, in an acute study, IF did not adversely impact muscle protein synthesis.
“IF promotes fat loss, without eating less”
Broadly True. IF was found to be potentially equal to, but not necessarily better than, eating less.
“IF provides metabolic benefits for general health”
Broadly True. IF (perhaps counterintuitively) decreases the risk of insulin resistance, and also has anti-inflammatory effects, benefits a healthy gut microbiome, and promotes healthy autophagy (which as we noted in a previous edition of 10almonds, is important against both aging and cancer)
However, results vary according to which protocol you’re observing…
For what it’s worth, 16:8 is perhaps the most-studied protocol. Because such studies tend to have the eating window from midday to 8pm, this means that—going against popular wisdom—part of the advice here is basically “skip breakfast”.
“Unlike caloric restriction, IF is sustainable and healthy as a long-term protocol”
Broadly True. Of course, there’s a slight loophole here in that IF is loosely defined—technically everyone fasts while they’re sleeping, at the very least!
However, for the most commonly-studied IF method (16:8), this is generally very sustainable and healthy and for most people.
On the other hand, a more extreme method such as Alternate Day Fasting, may be trickier to sustain (even if it remains healthy to do so), because it’s been found that hunger does not decrease on fasting days—ie, the body does not “get used to it”.
The American Journal of Clinical Nutrition wrote:
❝Alternate-day fasting was feasible in nonobese subjects, and fat oxidation increased. However, hunger on fasting days did not decrease, perhaps indicating the unlikelihood of continuing this diet for extended periods of time. Adding one small meal on a fasting day may make this approach to dietary restriction more acceptable.❞
“IF improves mood and cognition”
Mix of True and False (plus an honest “We Don’t Know” from researchers).
Many studies have found benefits to both mood and cognition, but in the short-term, fasting can make people “hangry” (or: “experience irritability due to low blood sugar levels”, as the scientists put it), and in the long term, it can worsen symptoms of depression for those who already experience such—although some studies have found it can help alleviate depressive symptoms.
Basically this is one where researchers typically append the words “more research is needed” to their summaries.
“Anyone can do IF”
Definitely False, unless going by the absolute broadest possible interpretation of what constitutes “Intermittent Fasting” to the point of disingenuity.
For example, if you are Type 1 Diabetic, and your blood sugars are hypo, and you wait until tomorrow to correct that, you will stand a good chance of going into a coma instead. So please don’t.
(On the other hand, IF may help achieve remission of type 2 diabetes)
Lastly, IF is broadly not recommend to children and adolescents, anyone pregnant or breastfeeding, and certain underlying health conditions not mentioned above (we’re not going to try to give an exhaustive list here, but basically, if you have a chronic health condition, we recommend you check with your doctor first).
📱 WHICH APP?
Choosing a fasting app
Thinking of giving IF a try and would like a little extra help? We’ve got you covered!
Check out: Livewire’s 7 Best Intermittent Fasting Apps of 2023
Prefer to just trust us with a recommendation?
We like BodyFast—it’s #2 on Lifewire’s list, but it has an array of pre-set plans to choose from (unlike Lifewire’s #1, Zero), and plenty of clear tracking, scheduling help, and motivational features.
Both are available on both iOS and Android:
