Health library

Why we gain weight

Weight gain often comes down to calories: Eat more than you burn, and the pounds may pile up over time. But there are a variety of other factors that can also play a role. Knowing what they are can help you understand how to best keep your weight in a healthy range.

Physical activity

Long periods of sitting and a lack of regular physical activity can increase your risk for weight gain.

Adults should get at least 150 minutes of physical activity every week—and kids should get 60 minutes a day. Doing weight-bearing exercises that work your major muscle groups at least two days a week is also important. Learn more about exercise and good health.

Diet and eating habits

Calories aren't the only dietary factor that can influence your weight. Consuming foods high in saturated fat or sugar can also cause you to put on extra pounds.

To eat healthier, choose foods like fresh fruits and vegetables, whole grains, lean proteins, and low-fat or fat-free dairy. Minimize processed foods and sweets, which are high in sugar and saturated fat, as well as sugary or alcoholic drinks, which have a lot of calories.

Stress

There's a good reason that feeling anxious or stressed tends to lead to overeating. Stress affects your brain and can trigger changes in hormones like cortisol, which controls energy balance and hunger urges. As a result, you may eat (and store) more fat.

While you can't always avoid stress, there are things you can do to cope. Take this stress assessment to learn more.

Sleep

As with stress, inadequate sleep can affect hormones that control hunger urges. This can make you want to overeat.

Strive to get the rest you need—at least seven hours a night, if you're an adult, and more if you're a child or teen.

Environment

Where someone lives and works can influence their ability to maintain a healthy weight. For example, not having access to parks, sidewalks or grocery stores that offer affordable, healthy foods can make it difficult to stay active and eat right.

Genetics

Genetic disorders, like Prater-Willi syndrome, can directly cause obesity. A person's genes can also influence their weight by affecting their hunger level. Fortunately, genes often work in combination with lifestyle factors like diet and exercise to cause weight gain. While you can't control your genes, you can do something about these other factors.

Health conditions and medications

Certain conditions, like polycystic ovary syndrome or an underactive thyroid, can cause weight gain. And some medications, including steroids and some antidepressants, can contribute to weight gain by disrupting chemical signals in the brain.

Your doctor can tell you whether a medical condition or a medication might be affecting your weight.

Are you a candidate for bariatric surgery?

For some people, lifestyle changes alone aren't enough to get rid of extra pounds.

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