Here's Why You're Gaining Weight After You Start Exercising

Mallory Creveling
Photo credit: PeopleImages - Getty Images

From Prevention

You kicked up your workout routine, squeezing in a few solid days a week of sweat, and eating a balanced diet filled with plenty of nutritious foods. You feel like you're well on your way to tipping the scale, but when you finally step on, the numbers say otherwise.

Well, listen up: You’re not alone. Research shows that while some people lose weight from exercise alone, most people do not. There are a lot of factors that come into play when it comes to weight loss, including some lifestyle choices and health habits that can cause you to put on pounds even when you're putting in the work. Here are some reasons you might not be seeing the results you wanted from your workout:

1. You’re giving the number on the scale too much credit.

There are a variety of reasons you shouldn't mind the number on the scale as much. There are days when you eat and drink differently, sweat more because of the workout you're doing or the temperature outside, sleep less from stress, etc. The list goes on. The number on the scale could teeter for all of these reasons.

Instead, take a step off the scale and assess the other benefits you might have gained from your newfound exercise routine. Do you have more energy? Do your clothes fit a little looser? Do you feel stronger carrying groceries or putting a suitcase in an overhead bin? Are you feeling all-around happier, more motivated, or less stressed? Did your overall health improve? These are the benefits of exercise that matter more than the pounds you've lost—and that should keep you motivated.

"It’s ultimately about how you’re feeling," says Jason Machowsky, RD, CSCS, clinical supervisor of performance services at the Hospital for Special Surgery in New York City. “Look for other measurements of exercise working—weight is not the only measure of success.”

2. You’re consuming more calories than you’re burning.

It’s super common for your appetite to turn up just as your fitness hits full blast, says Torey Armul, RD, spokesperson for the Academy of Nutrition and Dietetics. In fact, a June 2019 study from the Journal of Clinical Nutrition found that people tend to lose less weight than expected when they exercised because of an increase in appetite—and an increase in energy intake.

“When you start working out, your body starts burning more calories,” Armul explains. “And when you burn more calories, your body naturally wants to compensate by eating more calories to make up for what you’re burning.”

What’s more, people tend to overestimate how much they burn in a workout. Armul suggests keeping logs of how many calories you burn in a gym session, as well as tracking your food intake. Fitness trackers, like the Apple Watch and Fitbit, will tell you calories burned during exercise, while weight loss apps like MyFitnessPal offer easy food recording. You definitely don’t need to write down these numbers for months, but try a week or two just to see how your stats line up.

Armul also says it’s a red flag if you’re exercising only so you can eat more. "That’s a good theory, but you don’t want to use eating as an excuse to exercise," she says. "Make the goal getting healthy or fit or increasing athletic ability—not doing it just so you can eat more."

3. You might have a health issue.

If you’ve really been exercising, eating right, and getting enough sleep, but notice that your weight just keeps creeping up, you might want to see a doctor, says Machowsky.

Thyroid problems and certain medications can cause you to gain weight, no matter how much time and effort you put into eating healthy and working out. So if you’re feeling extra frustrated, don’t be afraid to talk to your doctor. They can rule out more serious health problems.

4. Your pre- or post-workout snacks aren’t the best choices.

As your appetite increases from burning more calories, it’s easy to reach for pre-packaged and processed foods that contain simple sugars, says Armul. But instead of filling your hunger with chips, cookies, or crackers, go for healthy post-workout snacks, such as fruits, veggies, lean protein, and healthy fats, so you get filling nutrients and likely in smaller portions.

While it’s beneficial to eat something after a workout to recover and rebuild, you don’t always have to have something. Machowsky says many people take in too many extra calories simply because they’re trying to eat a snack within 30 to 60 minutes of their workout. If you ate lunch or a mini meal an hour before you exercised, you probably don’t need something post-sweat, too.

On the flip side, if you don’t eat before your workout because you’re waiting for that post-activity re-fueling window, you might be left absolutely starving after exercise. That's also a safe bet for gaining weight. Reaching a state of extreme hunger tends to cause people to overeat, says Machowsky, so keep your satiety levels in check.

5. You’re eating too much protein or carbs.

Marathon runners might need to carbo load before the big day, but if your runs last less than an hour, you don’t necessarily need to fill up on carbs—the same goes for protein. Most Americans actually already get enough protein in their diets, says Armul, so you don’t need to focus so much on getting more of it—even if you’re weight training or HIIT-ing it more. “People love to talk about protein because it is essential, but if you eat too much, you’re going to gain weight, as it will be extra calories,” she says.

6. You’re not drinking enough water.

“I think people forget how much more fluid they need for exercising—you need to make sure you’re keeping up with your liquid needs,” Armul says. We often mistake thirst for hunger, so plan to ramp up your water intake as your pump up your workouts.

7. You’re not lifting weights.

Cardio increases your metabolism more, spiking hunger levels, but weight training offers a strong way to counteract that, says Armul. “Plus, when you gain muscle from lifting, you actually burn more calories at rest,” she says. “Lifting weights tends to not boost appetite as much as cardio, and it increases resting metabolic rate by accumulating lean muscle mass.” Even better, focusing on strength training can help you live longer—which is an even better pay-off than shedding a few pounds.

8. You’re only moving during your workout.

“The most common mistake is that people will work out and then their other daily exercise goes down,” says Machowsky. When you put so much emphasis on your gym time, but you sit a desk the rest of the day—or maybe you pushed it so hard that you don’t have energy to move for the next 24 hours—you could essentially keep your daily calorie burn hovering at the same spot as before your workout routine picked up. Remember to keep moving throughout the day by taking breaks to go for a walk or taking the stairs instead of the elevator. It’s not only your time spent in a scheduled sweat session that contributes to your overall calorie burn.

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