Why Can’t I Lose Weight? 11 Weird Reasons for Unexplained Weight Gain

Seeing extra pounds creep up on the scale or barely squeezing into a pair of lose pants can feel frustrating, especially if you’re following a healthy lifestyle. So what gives? The truth is that sometimes weight gain has nothing to do with what you’re eating or how much you’re working out. Here are other factors that could be standing between you and your ideal weight—plus expert tips on how to fix them.

You’re not sleeping enough

Skimping on shut-eye won’t just leave you tired the next day, but in the long run, it could cause you to pack on a few pounds. While researchers are still looking at the exact connection between lack of sleep and weight gain, Wendy Bennett, MD, MPH, says one reason may be that you’re simply awake longer, so you eat more overall. “You have a few more hours in your day, so you’re consuming more calories,” she says.

What’s more: Getting irregular zzz’s can mess with your circadian clock, which can interfere with hormone and metabolic regulation, Dr. Bennett says.

Isabel Maples, RD, a spokesperson for the Academy of Nutrition and Dietetics, echoes this theory. “When you’re not getting enough sleep, hormones change and you secrete a hormone that makes you hungrier, and less of the hormone that lets you know you’ve had enough to eat,” she says. What Maples is referring to is your ghrelin and leptin hormone levels. Ghrelin is known as the “hunger” hormone because it increases appetite, while leptin regulates energy and inhibits hunger. When you’re tired—like if you’re pulling an all nighter at work—you might reach for sugary and fatty foods to help you stay awake, but it increases your overall calorie intake.
Weight loss Rx: Focus on setting a regular sleep schedule, and aim to go to bed and wake up at the same time every day so your body gets into a regular circadian cycle, Dr. Bennett says. Be sure to practice good sleep hygiene by turning off electronic devices two hours before bedtime and avoid eating too close to the time you hit the hay. Limit your caffeine intake towards the end of the day if you have trouble falling asleep.

Here are more reasons you’re tired all the time:

You’re super stressed

Putting stress management on your health check list could have some physical benefits. You’ve probably heard of the stress hormone, cortisol, which protects your body from tense events. And while elevated levels of cortisol can be beneficial for short periods of time, chronic stress can wreck havoc on your body and lead to weight gain. “Basically your body thinks it needs to hold on to fat and calories,” says Dr. Bennett, who says this is because you almost go into survival mode.

A 2018 study from Cell Metabolism suggests there’s a connection between high levels of cortisol and fat mass. The study revealed that cortisol can affect a person’s circadian rhythm, and when the natural rise and fall of cortisol levels is negatively affected, it may cause weight gain. “People who are overwhelmed also have a hard time fitting in some things that we know are healthy for weight, like daily exercise or cooking for yourself,” Dr. Bennett explains.

Weight loss Rx: Michael Roizen, MD, chief wellness officer of the Wellness Institute at the Cleveland Clinic, suggests following consistent stress-relieving practices like deep breathing and meditation. He has seen patients lose weight by following these techniques regularly.

Bennett also recommends getting into a regular schedule with sleep and healthy activities, like meal prep and workouts. Add them to your calendar, and you’re likely to make them happen—and fight off weight gain because of it.

You’re depressed

Many anti-depressants cause weight gain, so if you’re depressed and are taking meds for it, expect to bump up your weight five to 15 pounds, with continued weight gain over the years, says Robert J. Hedaya, MD, a clinical professor of psychiatry at Georgetown University Medical Center. Research backs this up: In a 2015 study from General Hospital Psychiatry, of the 362 patients who were on antidepressants, more than 55 percent of them gained weight over a six- to 36-month period.

If you’re not taking antidepressant medication, there’s evidence that feelings of depression are associated with weight gain. One 2010 study in the American Journal of Public Health found that people who feel sad and lonely gain weight more quickly than those who report fewer depression-related symptoms. “They may be eating more high-fat, high-calorie comfort foods,” says Belinda Needham, PhD, assistant professor of epidemiology and co-director for the Center for Social Epidemiology and Population Health at the University of Michigan and the lead author of the study. “Or they may have [cut back their] physical activity.”

Weight loss Rx: “If I see patients who are taking anti-depressants and that could be the culprit of their weight gain, I may wean them slowly off of the drug,” says Dominique Fradin-Read, MD, MPH, assistant clinical professor at the Loma Linda School of Medicine in California. “I may then put them on Wellbutrin instead, which actually helps with weight loss.” If your meds are not to blame, seek out some workout buddies or a support group. “Attending meetings, like Weight Watchers, or working out with a group of friends is a great way to increase social support,” Dr. Needham says, “which can help depression.”

You’re taking the wrong medication

There’s a long list of medications that can cause weight gain: If you’re taking birth control pills, undergoing hormone therapy, taking steroids, using beta blockers for high blood pressure, anti-seizure meds, or breast cancer medications like Tamoxifen, you may notice the pounds piling on. Some treatments for rheumatoid arthritis and even some migraine and heartburn medications may cause weight gain.

“When I see patients who are concerned about weight gain, I start looking at their medications,” says Steven D. Wittlin, MD, clinical director of the endocrine-metabolism division at the University of Rochester Medical Center in Rochester, New York. “That’s a biggie. Some may affect appetite; some may affect metabolism.” Others may simply make you feel better and help you regain your appetite.

Weight loss Rx: If you suspect your medication is affecting your waistline, your doctor may be able to find an alternative treatment that won’t have that particular side effect.

Your gut microbiome is off

Digestive issues, including slow bowel movements, may also account for excess pounds. “Ideally, you eat, and then, an hour or so later, you have a bowel movement,” says Dr. Hedaya. “But once or twice a day is still in the healthy range.” If you’re not so regular, dehydration, medications, or low fiber could be to blame.

Another possible risk factor for weight gain could lie in your gut flora or microbiome. Several studies tie the mix of bacteria in your gut to weight gain, particularly if you don’t a balance of good and bad bacteria. It’s also one of the reasons artificial sweeteners have been linked to weight gain, as they can alter your gut microbiome. Dr. Roizen explains that the mix of bacteria in your gut can play a role in insulin resistance, which makes it difficult for your body’s cells to take in glucose, leading to weight gain.

Weight loss Rx: If constipation is your only symptom, then trying probiotics can help your digestive tract work properly. Staying hydrated is key, along with a diet chock-full of fiber-rich foods. You can also try drinking a fiber powder, like Metamucil, mixed with water. “It may even grab fat globules in your intestinal tract as it scrubs out waste,” says Dr. Hedaya. If you’re still having trouble, check with your doctor to rule out any diseases.

Your body’s missing certain nutrients

Having low levels of magnesium, iron or having a vitamin D deficiency can compromise your immune system, sap your energy levels, or alter your metabolism in ways that make it harder to take healthy steps. “You may compensate for low energy with caffeine, sweets, and simple carbs,” says Dr. Hedaya, “Or find that you feel too run down or weak to exercise.”

Weight loss Rx: While you can try to boost your iron levels by eating red meat and spinach and increase magnesium by adding Brazil nuts or almonds to your diet, it’s nearly impossible to consume enough milk or get enough sunlight to compensate for low vitamin D. “It’s important to know that it could take awhile to find your right dose of vitamin D,” says Dr. Hedaya. “If you take too much, you can get kidney stones. You need to have your blood tested every three months, so your doctor can make adjustments to the dose for you.” Adding an iron supplement is a little less tricky—but it’s still wise to let your doctor rule out hypothyroidism or other conditions that might cause insulin resistance before you start taking supplements.

You’re getting older

Aging is inevitable, but there are steps you can take to boost your metabolism. “Often, I hear patients tell me they think their metabolism is slowing down,” says Dr. Fradin-Read. “This is real—we don’t burn as many calories at 40 or 50 as we used to burn at 20. So we need more exercise—and less food—to keep metabolism going. Some studies show that exercise might be even more important than the diet for long-term weight maintenance.”

One reason you need exercise as you age: We lose muscle, says Maples. And the less muscle you have, the slower your metabolism. Aging and muscle loss can lead to weight gain both by causing an increase in fat mass and a decrease in how many calories your body burns at rest.

Weight loss Rx: Maintaining a regular exercise routine (one that includes strength training to build muscle) can help keep your body fat percentage down as you age, says Maples. Try to focus on staying hydrated and of course, eating more fruits and veggies, beans, lentils and whole grains. Follow these health screening guidelines for women after 40.

You have plantar fasciitis

“Many musculoskeletal conditions, including plantar fasciitis, but also osteoarthritis and knee or hip pain, can result in unintentional weight gain,” says Donald Bohay, MD, co-chairman of the public education committee for the American Orthopaedic Foot & Ankle Society. “Plantar fasciitis certainly can force you to cut back on your activity enough to cause weight gain.”

Weight loss Rx: Modify your exercise program to swap biking or swimming in place of weight-bearing exercise, says Dr. Bohay. Seek out a physical therapist who can design an appropriate program for your specific needs, and ask your doctor or check out the American Physical Therapy Association to find a qualified therapist in your area.

You’re eating late at night

Many researchers are looking into the timing of meals and how it relates to weight gain or loss. While the verdict is it still out the ideal eating schedule, one thing most experts agree on: Don’t eat late at night. Dr. Roizen mentions eating while watching TV at night can lead to mindless munching and calories your body doesn’t need. But there’s also a link to eating more at night, rather than in the afternoon or morning. “Data shows that eating at the end of your active period, as opposed to daytime, even if you eat the same number of calories at night as you do in the morning, you tend to gain weight,” Dr. Roizen explains.

A recent study backed this up, showing that people who saved their biggest meal of the day for dinner had a higher BMI than those who focused on eating more at breakfast or lunch.

Weight loss Rx: Have a hearty a.m. meal and lunch and pay attention to the number of calories you’re eating at dinner.

You forgot about the little things

Small changes to your daily lifestyle can add up big time when it comes to weight loss or gain. For instance, if you moved to a less walkable neighborhood, switched to a desk job, or started drinking more soda at lunch, a few weeks of these little tweaks can pile on pounds without you even realizing it, says Maples.

All experts mentioned that sugary drinks are a major factor people forget, especially when calorie counting. Your liquid calories can add up just as quickly as the ones you consume from food.

Weight loss Rx: The first step to learning how much you’re eating is to track your food intake for a few days, says Dr. Bennett. “People might not realize that they’re eating all day long or that they’re consuming high-calorie drinks,” she says. Once you have your meals written down and can see the full picture, you might be able to spot the tweaks you can make that will lead to big, weight-reducing results.

An unlikely possibility: You have Cushing’s syndrome

Weight gain accompanied by high blood pressure, osteoporosis, and changes in your skin tone and quality could be a sign that your body isn’t processing nutrients the way it should, due to a cortisol-producing tumor on one of your adrenal glands. The syndrome affects only about 15 in every 1 million adults annually, so proceed with caution before demanding a battery of tests. “Cushing’s Syndrome is not terribly common,” says Dr. Wittlin, “but one of the telltale signs is that your fat distribution is more in the midsection of your body, leaving your arms and legs looking more slender.” Purple or slivery stretch marks on your abdomen or ruddy cheeks are other signs.

Weight loss Rx: If you suspect you are gaining weight that you can’t attribute to your eating habits, medications, or lack of exercise, a few tests—including a blood test and a urinalysis to get an accurate check of your body’s cortisol levels—will give your doctor the first clues to this condition. If the levels are deemed excessively high, then your doctor will order more tests, like a CT scan of your pituitary and adrenal glands, to determine if a tumor exists. If the tumor is confirmed, doctors will likely perform surgery to remove the tumor (and possibly the affected gland). You might follow it up with a course of steroids to help regulate the remaining gland.

Mallory Creveling, an ACE-certified personal trainer and RRCA-certified run coach, joined the Runner’s World and Bicycling team in August 2021. She has more than a decade of experience covering fitness, health, and nutrition. As a freelance writer, her work appeared in Women’s Health, Self, Men’s Journal, Reader’s Digest, and more. She has also held staff editorial positions at Family Circle and Shape magazines, as well as DailyBurn.com. A former New Yorker/Brooklynite, she’s now based in Easton, PA.