Can Intermittent Fasting Cause Weight Gain?

Intermittent fasting has become more popular as an alternative to dieting because it's more concerned with when you eat than what you eat. Not only can you lose weight while intermittent fasting, but it could reduce oxidative stress, increase longevity, and help the body with cellular repair, according to Healthline.

You also have different ways of intermittent fasting. Some people commit to time-restricted eating, which might mean an eating window of eight or 12 hours every day. Other people might choose alternate-day fasting such as the 5:2 plan, where you eat unrestricted for five days a week and eat 500 to 600 calories on two non-consecutive days a week. More extreme versions of these intermittent fasts might have you fasting from food altogether a few days a week or every other day.

The type of intermittent fast, your body type, and how many calories you're cutting can determine how much weight you lose, according to Women's Health. However, these factors could also lead to gaining weight during intermittent fasting.

Intermittent fasting is really about cutting the total amount of calories you're consuming, according to Women's Health. If you're eating more calories than your body burns off, you could be picking up a few pounds. Even though intermittent fasting isn't about counting calories, you could be consuming a lot more food during your eating window than you realize. For a few days, it might be helpful to track your food intake to give you a rough estimate of how many calories you're taking in.

You could also gain weight during an intermittent fast if the fasting method doesn't suit your lifestyle. For example, an eight-hour eating window that skips breakfast might not be suitable for an endurance athlete who works out in the morning. Exercising too much can also stoke your hunger, particularly if you exercise in a fasted state. This might cause you to overeat during your eating intervals.

If you eat mostly junk food while intermittent fasting, you could also be consuming more calories than you think. It's best to choose nutrient-dense food such as lean proteins, fiber-rich carbohydrates, and healthy fats. It's also possible that you're not eating enough to sustain your body's energy needs, so your body tries to adapt to conserve energy.

A 2022 meta-analysis in Obesity compared alternate-day fasting, time-restricted eating, and basic calorie restriction. Alternate-day fasting led to slightly more weight loss than the other two methods. This might not be appropriate to your lifestyle or might be difficult to sustain for a long time, however. According to Medical News Today, it's important to stay hydrated during your fasting intervals. To avoid thinking about food, find a healthy means of distraction and be sure to rest and relax during the fasting intervals.

If you're not losing weight through intermittent fasting, you might consider another method of weight loss. A 2023 study in the Journal of the American Heart Association followed more than 500 people for six years and found that people who ate small but frequent meals had lost more weight than people who followed time-restricted eating patterns. People who tended toward larger meals tended to gain weight. According to The Conversation, it's possible for you to regain any lost weight if you stop intermittent fasting.