Is Intermittent Fasting Making You Gain Weight? One of These 6 Reasons Could Be the Culprit

“Intermittent fasting doesn’t guarantee weight loss. Some studies have shown it can be beneficial for weight loss or weight-loss management but not if you’re eating excessive amounts of food during your eating window,” registered dietitian nutritionist and NASM-certified trainer Whitney English Tabaie, MS, RDN, CPT, told POPSUGAR.

Intermittent fasting works because limiting your eating window is a means of calorie restriction and eating fewer calories than you burn helps with weight loss.

But if you’re eating from the minute your window opens to the very last second that your window closes (just one more handful of popcorn!), and you’re eating past the point of fullness to discomfort or pain, it can lead to weight gain.

Tabaie added that fasting isn’t for everyone. She explained that for some people, restricting eating hours “can lead to binge eating, which would be counterproductive to weight-loss attempts. This is why I recommend intermittent fasting for potential health benefits and not as a weight-loss strategy.”

Ensure that you’re eating enough calories during your window. If you don’t, registered dietitian Leslie Langevin, MS, and author of The Anti-Inflammatory Kitchen Cookbook, explained that it can cause “the binge and restrict cycle.” If you don’t eat enough on Monday and then on Tuesday you end up bingeing, if this cycle continues, it can lead to weight gain. And if being too hungry makes you eat outside of your planned window, it means you’re not being consistent with IF.

In making sure you eat enough, you don’t want to dip under 1,200 calories daily. If you do, then intermittent fasting may not be the cause for your weight gain, it’s just the fact that you’re not eating enough on some days and then eating too much on other days. In this case, intermittent fasting might not be for you, especially if you have a history of disordered eating.

If you are caught in this cycle, Langevin suggested reducing your fasting window to maybe 12 or 14 hours. “This can still be helpful and reduce the time of eating in the day so the body is in calorie-burning mode more of the time, but still provides a longer window of eating.”

One of the bonuses about the intermittent fasting lifestyle is that no food is off limits. While you can eat high-carb foods like pasta, pizza, bread, and fruit smoothies, you want to make sure that you’re eating enough protein to prevent hunger. If you don’t, you’ll end up feeling hungry, which can result in you eating more. Langevin said, “The basic idea is that IF is a tool, but if you’re not paying attention to calorie intake, or a balanced intake during your eating window, that can backfire,” and result in weight gain.

Eating sugary foods and refined carbs like pasta, bread, sweeteners, and dessert don’t cause weight gain just because they tend to be high in calories – these foods affect your insulin levels. Jason Fung, MD, a nephrologist (kidney specialist) and author of The Complete Guide to Fasting, explained to POPSUGAR that these foods spike your insulin levels. When insulin levels are high, it signals your body to store fat, which can lead to weight gain.

Eating these types of foods can also make you eat more in general, explained Susan Peirce Thompson, a psychology professor with a Ph.D. in brain and cognitive sciences. When eating sugar elevates insulin levels, it blocks leptin (the hormone that signals to your body that you’re full). If your brain doesn’t get the message that it’s had enough, it’ll signal to your body to keep eating.

Eating sugary foods also makes you want them more. That’s because sugar overloads your dopamine receptors, leading to strong and insatiable cravings. In Thompson’s book Bright Line Eating, she explained that this is why you eat cookie after cookie and still want more.

You don’t need to ditch all carbs, though. Opt for complex carbs like whole grains, beans, veggies, and fruits. Langevin said to aim for three servings a day of whole grains, one to two of fruit, and one to two of legumes.

While fueling after a workout is important, just because you go for a 30-minute run AND you do intermittent fasting, it doesn’t mean you can eat whatever you want. How much you eat still matters. Depending on your weight and the pace of your run, that half-hour run only burned between 200 and 400 calories. So you can’t go overboard and inhale 5,000 calories during your eating window and still expect to lose weight.

Langevin added to utilize mindful eating. “Eat when you are truly hungry, and make sure to stop eating when you’re full.”

There are several intermittent fasting methods, and some are more strict than others. This could leave “someone famished, leading to overeating later on,” registered dietitian Rachel Stahl, MS, RD, CDN, CDE, explained.

The 20:4 method, where you only have a four-hour eating window every day, may leave you feeling ravenous once your eating window opens, so you end up eating more calories than if you weren’t doing IF at all.

Your IF lifestyle should feel easy and effortless, and definitely shouldn’t leave you feeling so starving that you binge. Try different methods to see if they work better for you, or consider that IF might not be for you.