You may know somebody who’s doing intermittent fasting. You may have considered it. Or even tried it yourself. It’s one of the most popular health and weight loss strategies at the moment.
It’s true that there are tremendous health benefits to intermittent fasting. And it can be an effective weight loss strategy as well. But as with any dietary protocol, it’s important to know what you’re doing to optimize results and avoid potential pitfalls.
What is intermittent fasting?
One of the best things about intermittent fasting is its simplicity. Fasting is simply the act of not eating. To do so intermittently means to not do so continuously – to start and stop. In other words, intermittent fasting involves periods of not eating interspersed with periods of eating.
The most common way people practice intermittent fasting is also know as time-restricted eating. A person may restrict eating to an eight-hour window, for example, and fast for the remaining sixteen hours of the day.
Other ways to approach intermittent fasting are to fast for a full 36 hours every other day; the practice of “alternate-day fasting.” Or to fast one full day per week for 40 hours.
There are virtually an infinite number of ways to engage intermittent fasting. But what are the benefits?
Intermittent fasting helps reverse insulin resistance
When we eat three meals per day, plus snacks, our body produces enough insulin to drive unused glucose and fatty acids into our liver and fat cells. This process is an important evolutionary adaptation which has allowed our species to store excess energy for times of food scarcity.
The problem, though, is that when we eat all day, every day, our body never gets the opportunity to use that stored energy. Our liver and fat cells become full, making it harder for insulin to do its job, to drive energy into our cells. In response, our body produces more and more insulin. And the higher our insulin levels become, the more stuffed our cells become, until our cells start to “resist” insulin.
This is the vicious cycle known as insulin resistance, which left unchecked results in type 2 diabetes.
The good news is that when we fast, our insulin levels drop, giving our body a chance to access stored energy. The longer and more often we fast, the more our body relies on stored energy for fuel. This is what is referred to in common speech as “burning fat.”
As we deplete our fat cells of stored energy, we are making room for new energy to be stored the next time we eat. Our post-meal blood sugar levels return to baseline faster. We’ve become more sensitive to insulin.
One of the primary benefits of intermittent fasting is the way it improves insulin sensitivity.
Intermittent fasting helps with weight loss
Another way to look at insulin is that it is a fat-storing hormone. Prolonged elevated insulin levels lead to weight gain, obesity, and the health complications that accompany it. Losing weight can be as simple as lowering insulin levels long enough and often enough to give our body a chance to burn through stored energy.
It’s also the case that eating less often leads to fewer calories consumed. And that can help with weight loss, but calories are not the most important factor in weight loss.
What makes intermittent fasting so effective is that it improves the efficiency with which we metabolize food. Fasting boosts our metabolism so that we can more efficiently extract the nutrients from food when we do eat.
A healthy metabolism and control of insulin are the keys to weight loss. Fasting helps with both.
Intermittent fasting cleans up damaged cells
Intermittent fasting stimulates a process called autophagy. Autophagy is the body’s way of clearing damaged cells. Our body is constantly generating new cells as old ones are damaged and die off. Autophagy is the process by which our body “eats” dead and damaged cells to make room for new ones. We are self-cleansing machines.
When we give our body a break from the work of digesting food and storing energy, self-cleansing can take place. Since cancer (as well as other diseases) is attributed to damaged cells, some researchers believe that autophagy can be a factor in cancer prevention.
Think of a gasoline combustion engine. Oil is used to lubricate the moving parts, but as gas is burned, the oil is degraded and needs to be changed every 3,000 miles or so before it “gunks” up the works. Our damaged cells are like that degraded oil. You could liken autophagy to an oil change. It cleans out the gunk and helps your body run smoothly.
Also, while fasting instigates autophagy, it also stimulates growth hormone, which quickens the generation of new cells. As autophagy drains the old oil from our combustion engine, growth hormone adds fresh oil to the mix.
How to get started
The easiest way to get started with intermittent fasting is with a 16/8 schedule. This means that you do all your eating in an eight-hour window and fast the remaining sixteen hours. You can easily do this by skipping breakfast or dinner. For example, if you finish eating dinner by 7pm, skip breakfast the next morning, and eat an early lunch at 11am, you’ve fasted for 16 hours. If you wish, you can have a snack between lunch and dinner and you still will have stayed within your eight-hour window.
There are a number of phone apps on the market that make it easy to track your meal times. I use an app called Zero. It’s free to download and simple to use. You can set whatever fasting schedule you desire, start your fast at the end of the day’s last meal, and it will start a timer for you. I like this approach because I always know exactly how long I’ve been fasting. I don’t have to keep track in my head.
You don’t necessarily need to change your diet to get started with fasting, but you may find that focusing on whole foods while eliminating sugar and refined grains will make things a lot easier. The reason for this is that your body is capable of running on two fuel sources – glucose and fat. When you eat a diet high in sugar and refined carbohydrates, your body gets used to burning glucose for energy and you will crave it when the supply runs dry.
When fasting, on the other hand, your body relies on fat for fuel. To this end, you may find that a diet higher in healthy fats and lower in refined carbohydrates makes your fasting periods feel easier. Your body will get used to burning fat for fuel and the switch to burning its own fat during fasting periods will feel more natural.
It’s also important to optimize protein when you do eat to make sure that your body has the building blocks it needs to maintain lean muscle mass. You want to lose fat, but you don’t want to lose muscle!
And don’t forget the salt. Your kidneys will filter out more salt from your blood stream during fasting periods, so it’s crucial to replenish. I recommend high quality sea salt as opposed to table salt. You should salt your food liberally to taste and can supplement that by squeezing half a lemon into a glass of water, mixing in a teaspoon of sea salt, and drinking that down once a day.
Final tips and a word of caution
- Don’t restrict calories. When you do eat, eat until you are full. You may find that you are eating two large meals a day as opposed to three smaller meals with snacks. And that’s perfectly fine. It’s important to replenish your system with the nutrients it needs between fasting periods.
- You can drink coffee, tea, or water during fasting periods, but keep in mind that adding cream, milk, or sweeteners will technically break your fast and diminish the benefits. Learn to enjoy your coffee or tea black. I certainly do!
- If you are diabetic and taking medication to lower your blood sugar, you should not fast without the supervision of a medical professional. Your blood sugar will drop during fasting periods and your medications will lower it further, potentially to dangerous levels. You must have a medical professional monitoring your blood sugar and adjusting your medication dosage appropriately.
- Fasting should not be too difficult. If you are 10 to 14 hours into a fast and find yourself really struggling with hunger or feeling faint, go ahead and eat. It’s perfectly okay as a beginner to start with 12 to 14 hour fasts and work your way up from there.
For an in-depth study of therapeutic fasting protocols, I recommend the following three books by Dr. Jason Fung:
(A version of this article first appeared in the December 2000 issue of STOLZ magazine.)