Intermittent fasting is a popular diet trend of the moment. What is it, how do you do it, and should you be intermittent fasting for weight loss?
What is intermittent fasting?
Intermittent fasting (IF) is a popular diet and style of eating that involves periods of eating and abstaining from eating. There are several styles of IF, but in general, a person will eat whatever they want within a constricted timeframe, and fast during the rest of the time.
Many people try intermittent fasting for weight loss. Supporters claim that IF creates metabolic changes that make it a more effective tool for weight loss than traditional caloric restriction. Is it easier to lose weight on IF because of metabolic changes in your body? Read on to find out.
Styles of intermittent fasting
There are several intermittent fasting schedules people may choose to follow. The most common involve alternate day fasting, modified fasting regimens, and time-restricted feeding (1).
Alternate Day Fasting: This style combines fasting days when nothing is consumed, and feeding days, when you can eat and drink whatever you want.
Modified Fasting Regimen: Similar to alternate day fasting, a modified fasting regimen involves days where you eat and drink whatever you want. But, instead of completely fasting on fasting days, you severely restrict your intake to 20-25% of your energy needs.
Time-Restricted Feeding: During time-restricted feeding, you eat food every day but within a predetermined time restraint. Therefore, you are fasting from ~12-21 hours each day.
What are the weight loss benefits?
Proponents of IF proclaim it has several health benefits including weight loss. Some think that IF causes increased fat loss due to lower levels of insulin in the body during fasting. Insulin is a hormone that helps our cells store energy from food. The pancreas releases insulin in response to eating food.
Support for IF says if we fast long enough, we don’t produce insulin to store food as energy. Therefore, we turn to stored energy in the form of fat, making IF more efficient for weight loss than traditional caloric restriction. Human studies have found IF can be a successful tool for weight loss (2, 3, 4, 5). But, is IF more effective for weight loss than traditional caloric restriction?
Caloric restriction for weight loss simply means you are consuming less energy than your body needs to maintain its current weight. You need to create a caloric deficit to lose weight. One pound of weight loss = cutting 3500 calories. This rule of thumb is the scientifically accepted number for weight loss.
Should you try intermittent fasting for weight loss?
Taken as a whole, IF and weight loss research can be widely attributed to the fact that IF causes a caloric deficit, and therefore produces weight loss (1, 2, 6, 7). If you’re losing weight doing intermittent fasting, it’s because you’ve created a caloric deficit.
Overall, the research supports a recommendation that intermittent fasting is a viable alternative to caloric restriction, but it is not superior. For weight loss, it doesn’t matter what time you eat, as long as you are eating less than your body needs so it burns stored energy.
It all comes down to lifestyle! Everybody is different, and what works for one person may not work for another. If your schedule allows for fasting, and you are able to do so without feeling hungry, tired, or low energy, go for it. But, if you know you need breakfast to be productive during the day, traditional caloric restriction is probably better for you.