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.❞

American Journal of Clinical Nutrition

“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:

See the BodyFast App / See the Zero App

Breakfast Time!

In yesterday’s newsletter, we asked you for your health-related opinions on the timings of meals.

But what does the science say?

Quick recap on intermittent fasting first:

Today’s article will rely somewhat on at least a basic knowledge of intermittent fasting, what it is, and how and why it works.

Armed with that knowledge, we can look at when it is good to break the fast (i.e. breakfast) and when it is good to begin the fast (i.e. eat the last meal of the day).

So, if you’d like a quick refresher on intermittent fasting, here it is:

Intermittent Fasting: We Sort The Science From The Hype

And now, onwards!

One should eat breakfast first thing: True or False?

True! Give or take one’s definition of “first thing”. We did a main feature about this previously, and you can read a lot about the science of it, and see links to studies:

The Circadian Rhythm: Far More Than Most People Know

In case you don’t have time to read that now, we’ll summarize the most relevant-to-today’s-article conclusion:

The optimal time to breakfast is around 10am (this is based on getting sunlight around 8:30am, so adjust if this is different for you)

It doesn’t matter when we eat; calories are calories & nutrients are nutrients: True or False?

Broadly False, for practical purposes. Because, indeed calories are calories and nutrients are nutrients at any hour, but the body will do different things with them depending on where we are in the circadian cycle.

For example, this study in the Journal of Nutrition found…

❝Our results suggest that in relatively healthy adults, eating less frequently, no snacking, consuming breakfast, and eating the largest meal in the morning may be effective methods for preventing long-term weight gain.

Eating breakfast and lunch 5-6 h apart and making the overnight fast last 18-19 h may be a useful practical strategy.❞

~ Dr. Hana Kahleova et al.

Read in full: Meal Frequency and Timing Are Associated with Changes in Body Mass Index

We should avoid eating too late at night: True or False?

False per se, True in the context of the above. Allow us to clarify:

There is nothing inherently bad about eating late at night; there is no “bonus calorie happy hour” before bed.

However…

If we are eating late at night, that makes it difficult to breakfast in the morning (as is ideal) and still maintain a >16hr fasting window as is optimal, per:

❝the effects of the main forms of fasting, activating the metabolic switch from glucose to fat and ketones (G-to-K), starting 12-16 h after cessation or strong reduction of food intake❞

~ Dr. Françoise Wilhelmi de Toledo et al.

Read in full: Unravelling the health effects of fasting: a long road from obesity treatment to healthy life span increase and improved cognition

So in other words: since the benefits of intermittent fasting start at 12 hours into the fast, you’re not going to get them if you’re breakfasting at 10am and also eating in the evening.

Summary:

• It is best to eat breakfast around 10am, generally (ideally after some sunlight and exercise)
• While there’s nothing wrong with eating in the evening per se, doing so means that a 10am breakfast will eliminate any fasting benefits you might otherwise get
• If a “one meal a day, and that meal is breakfast” lifestyle doesn’t suit you, then one possible good compromise is to have a large breakfast, and then a smaller meal in the late afternoon / early evening.

One last tip: the above is good, science-based information. Use it (or don’t), as you see fit. We’re not the boss of you:

• Maybe you care most about getting the best circadian rhythm benefits, in which case, prioritizing breakfast being a) in the morning and b) the largest meal of the day, is key
• Maybe you care most about getting the best intermittent fasting benefits, in which case, for many people’s lifestyle, a fine option is skipping eating in the morning, and having one meal in the late afternoon / early evening.

Take care!