Intermittent fasting for weight loss is all about when you eat rather than what you’re eating!
In this way, it’s more accurately described as an eating pattern instead of a diet.
Although there are several ways to go about intermittent fasting for weight loss, all methods involve dividing the day or week into periods of eating versus not eating. It’s genuinely that simple.
During periods of fasting, you may drink black coffee, water, and unsweetened tea - but, generally speaking, you may eat little or nothing at all.
Some experts allow for bone broth as well as small amounts of cream, half and half, whole milk, or unsweetened almond milk in your coffee or tea.
The most popular methods of intermittent fasting for weight loss are:
Eat-Stop-Eat: Abstain from food for 24 hours, once or twice a week. For example, enjoy breakfast one morning and wait until breakfast the next morning to eat again.
The 5:2 diet: Eat only 600 calories on two non-consecutive days of the week. Eat as you usually do the other 5 days.
The 16/8 method: Also called The Leangains Protocol. Skip breakfast and restrict your daily eating period to an 8-hour window. Then, fast for 16 hours in between.
This diet has somewhat misleadingly been dubbed the “8-hour diet” - sending unsuspecting dieters down a rabbit hole in which they believe that they can lose unwanted weight in - you guessed it - 8 hours.
Most of us find the 16/8 method to be the easiest and most sustainable method to stick to. For this reason it is by far the most popular.
Note: Overall calories do matter in The Leangains Protocol, contrary to what some IG bloggers might tell you. Most people cannot eat 4,000 calories in their 8-hour window and expect to feel fantastic - or, for that matter, not gain weight. Speak to a nutritionist to set realistic numbers for what your caloric intake should be based on your weight loss goals.
So, why fast?
Jason Fung, PhD has written an extraordinary book titled The Obesity Code, which not only offers invaluable nutrition advice - it also delivers evidence-based, research-backed data calling out the socioeconomic influences that makes us fat.
He writes with great humor and grace - I highly recommend the book (you will never think about snacking the same way again). Fung is clear:
“The body only exists in two states - the fed state and the fasted state. Either we are storing food energy (increasing stores), or we are burning stored energy (decreasing stores). It’s one or the other. Intermittent fasting for weight loss allows the body to use its stored energy. The important thing to understand is that there is nothing wrong with that.”
Beyond this, there are many other compelling reasons to fast. Including the following...
Better Insulin Sensitivity and Nutrient Absorption
The body secretes insulin when we eat. Spiking insulin too much and too often can desensitize our body to its effects. Taking breaks from eating is one way to help with insulin sensitivity which may improve body composition.
Better Fat Metabolism
Some research suggests that exercising while fasting produces greater fat metabolism when compared to fed training. So, you may burn more fat if you’re working out on an empty stomach.
Many small meals throughout the day may make it harder for you to control your appetite!
This is because ghrelin, the hunger hormone, is secreted based on when you usually eat. If you are snacking all the time, you will secrete ghrelin… all the time.
Faster Fat Loss
By reducing your caloric intake, all of these methods should induce weight loss - as long as you don’t compensate by eating more when you break the fast.
Are there any other benefits to intermittent fasting for weight loss?
Yes! Fasting triggers autophagy, and there is no other means to enter this state.
When implemented correctly, intermittent fasting for weight loss can effectively reduce body fat over time. But, it’s also crucial as a protective anti-aging mechanism.
What is autophagy?
After 12 hours of fasting, you’ve entered a metabolic state called ketosis. In this state, your body starts to break down and burn fat.
By the 18-hour mark, you’ve switched to fat-burning mode and are generating significant ketones.
Within 24 hours, your cells are increasingly recycling old components and breaking down misfolded proteins linked to Alzheimer’s and other diseases. This is the process called autophagy.
As far as cellular and tissue rejuvenation go, autophagy is crucial: not only does it remove damaged cellular components including misfolded proteins, it wards off neurodegenerative diseases in the process.
Other interesting points to note...
After 48 hours with few or no calories HGH, your growth hormone is five times higher than when your fast began.
Growth hormone triggers a process called lipolysis, an enzymatic reaction in cells that breaks down fat. It also inhibits the effect of insulin, promoting the destruction of fat cells. Nice! ☺
By the 54-hour mark, insulin levels have dropped to their lowest point - your body is becoming increasingly insulin-sensitive. Remember, increased insulin sensitivity reduces fat storage as well as inflammation and protects you from chronic diseases associated with aging (some cancers).
Restrictive eating plans like The Prolon Diet claim to trigger autophagy while still allowing you to eat a certain amount of food. It is extensively researched and most likely works.
I will say, in my experience with clients, most of the weight lost on this diet (usually 5 lbs) returns within 2-3 weeks. So, I would NOT recommend it as a weight loss diet, only for the benefits of autophagy.
Avoid sugars and refined grains. Instead, eat a primarily plant-based diet. Add in lean proteins.
Let your body burn fat between meals.
Consider intermittent fasting for weight loss. Limit the hours you eat, and ideally, eat earlier in the day. 11 AM to 7 PM is far better than 3 PM to 10 PM.
Avoid snacking or eating at nighttime - all the time!! 🦉
Make more room for protein. Protein is very satiating and because of its thermic effect, you burn more calories digesting protein than the other macros.
Some experts suggest that protein should actually count for 3.2 calories per gram instead of the 4 calories per gram commonly cited. I strongly support this notion!
Is intermittent fasting for weight loss for everyone?
Fasting has been practiced throughout human evolution.
Ancient hunter-gatherers didn’t have supermarkets or refrigerators - and sometimes, couldn’t find anything to eat.
As a result, humans evolved to be able to function without food for extended periods of time. Fasting is in fact more natural than always eating - and perfectly safe for MOST people.
Fasting is also often done for religious or spiritual reasons, including in Islam, Christianity, Judaism, and Buddhism.
For certain people, fasting is not advisable! Although it could be a wonderful solution for you one year, it could be a terrible idea the next.
If lifestyle changes (a new baby or job) crop up, this diet could do more harm than good. It’s important when considering any nutrition program to remember that just because something works for you right now, it won’t necessarily work for everyone, in every situation forever.
In other words, don’t insist your friends do it just because it’s working so well for you! ☺
- Sophie Anson & the NutriSuits team
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Halton TL, et al. The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. J Am Coll Nutr. 2004 Oct;23(5):373-85.
Livesey G. A perspective on food energy standards for nutrition labelling. Br J Nutr. 2001 Mar;85(3):271-87.
Effects of intermittent fasting on health, aging, and disease. de Cabo R, Mattonson MP. New England Journal of Medicine, December 2019.
Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism. American Journal of Clinical Nutrition, January 2005.
The Obesity Code, by Jason Fung, MD (Greystone Books, 2016).
Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Database of Systematic Reviews and Implementation Reports, February 2018.
Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition, August 2017.
Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism, May 2018