Everyday Health

6 Sneaky Reasons You’re Gaining Weight

Originally published February 24, 2020

Last updated April 29, 2024

Reading Time: 5 minutes

If your clothes are getting tight or the number on the scale is going up, one of these issues could be the reason why.

If you’ve noticed that the number on your scale is quickly rising or that your clothes have gotten snug, but your eating patterns and activity level haven’t changed, you might want to consider what else could be behind your sudden weight gain.

While there is no specific definition for what is considered rapid weight gain, it shouldn’t be ignored, according to Kurt Hong, MD, an internal medicine physician at Keck Medicine of USC, who is dual board certified in internal medicine and clinical nutrition.

“Rapid weight gain is weight gain that’s going to be sustained,” Dr. Hong says. “It’s not so much just centered around a specific amount of weight gained in a certain period. It’s important to determine whether there are also other symptoms that could suggest something is going wrong. But it’s one thing to gain 10 pounds over a period of a couple of years; it’s another thing to gain 10 pounds in a month.” 

But still, most people’s weight can fluctuate daily, depending on factors like how much water they drink and how much they exercise. 

“My key advice for anybody who’s experiencing unexplained weight gain is to speak either with your dietitian or with your primary care doctor so that they can run an appropriate blood panel to determine your cause of weight gain,” he says. 

Here are some possible explanations. 

1. Menopause

Around menopause, women may gain weight more easily.  

Menopause can cause weight gain for a number of reasons, Dr. Hong says.  

“Usually, with the hormonal changes related to menopause, not only do you see a drop in the estrogen and progesterone levels, sometimes, there’s also a drop in testosterone levels,” he says.  

Loss of testosterone often leads to a loss in lean muscle mass, which can occur 12 to 18 months after the start of menopause. This can also contribute to weight gain. 

“Anytime you lose muscle, particularly if you’re not active or exercising regularly, there’s going to be a drop in your basal metabolic rate, which can actually make you more prone to gaining weight,” Dr. Hong says. 

2. Insomnia or disrupted sleep

If you’re not getting enough hours of sleep or have poor sleep with frequent wakings, you may be more likely to have excess weight. 

Although there are many studies supporting the correlation between poor sleep and weight gain, it’s hard to say which causes which.  

“It’s a little bit of the chicken or the egg story in the sense that sometimes weight gain can also affect your quality of sleep, because you may be more prone to obstructive sleep apnea,” Dr. Hong says. 

But, if you aren’t getting enough rest, it can actually slow down your metabolism and increase production of cortisol, which is a stress hormone, Dr. Hong says.  

“Sometimes, when patients are not sleeping well, it can also affect some of their stress levels, which can actually then lead to more stress-related cravings and overeating,” he says. 

3. Certain medications

There are many medications that may also indirectly or directly lead to gaining pounds. 

“Some medications can interfere with your metabolism, particularly your carbohydrate metabolism, by directly inducing more insulin resistance,” Dr. Hong says. “And there are some medications that can actually trigger cravings and hunger, which makes you eat more.” 

Examples of medications that may affect your weight include steroids, immunosuppressants, older generation beta-blockers used to treat tremors, anticancer medications, HIV medications and psychotropic medications that treat schizophrenia.

4. Mental health conditions, such as depression

Certain mental health conditions, such as depression and generalized anxiety disorder, can trigger eating-disorder-like behaviors, Dr. Hong says.  

“Sometimes, when people feel down or anxious, they can turn to food for comfort. Both depression and anxiety can also directly induce cravings and, sometimes, even hunger,” Dr. Hong says.  

But not everyone will experience similar symptoms. Some people will eat more if they feel upset, some will eat less.  

If someone has gained weight because they are depressed, it might also further exacerbate the problem.  

“Gaining weight when you’re depressed might affect your energy, your motivation and how you’re able to approach addressing your mental health issues. So, it’s really, really important to break that cycle.”  

Therapy or medications for more severe cases can be effective in this case, he says. 

5. Certain medical conditions

If you can’t otherwise account for your weight gain, your doctor may want to test you for certain endocrine disorders. The endocrine system, which includes adrenal glands, thyroid and ovaries, helps regulate hormones that control several functions in the body. 

“We look first to someone’s history to determine if there’s other medical issues or symptoms going on that might be also causing weight gain, such as hyperthyroidism or a pituitary issue, but these aren’t as common,” Dr. Hong says.  

6. Being unaware of your eating

“The most common cause of weight gain is probably still that people are just not aware of just how much they’re eating,” Dr. Hong says.  

As you get older, your metabolism slows down, but most people do not adjust their food intake to also be less. 

“We end up eating more calories than we are burning — this was particularly true for many people during the COVID-19 pandemic,” Dr. Hong says. “For a lot of people, their stress levels went up, and on top of that, they were less active because they were working from home.” 

The most common cause of weight gain is probably still that people are just not aware of just how much they’re eating.

Kurt Hong, MD, an internal medicine physician at Keck Medicine of USC 

If you’re struggling with rapid weight gain, timing is key for treatment. Dr. Hong recommends weighing yourself at home a few times a month to be able to notice if your weight is rapidly changing. 

“The sooner you seek help the better,” Dr. Hong says. “It’s much harder to treat someone after gaining 30 pounds versus 10 to 15 pounds. The sooner we treat the underlying problem the better.” 

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Mollie Barnes
Mollie Barnes is a writer and editor at Keck Medicine of USC.