As we age we naturally tend to gain weight, to the tune of 1 to 2 pounds (lb) per year, according to a review by the Agency for Healthcare Research and Quality. That may not seem like much, but over time it can lead to significant weight gain and, in some cases, obesity, which is considered to be a body mass index (BMI) of 30 or higher. “Obesity incidence starts increasing in one’s twenties and peaks at 40 to 59, and then decreases slightly after age 60,” says Craig Primack, MD, an obesity medicine physician at the Scottsdale Weight Loss Center in Arizona. Not everyone will become overweight as they age, because body weight is highly influenced by a person’s genetic makeup, level of physical activity, and food choices, Dr. Primack says. “We sometimes say genetics loads the gun and lifestyle pulls the trigger,” he says. Still, everyone will find it harder to maintain or lose weight with each passing year.

Weight Gain and Age: What’s Going On?

Our muscles, hormones, metabolism, and other body systems are in flux as we get older. (In other words, it’s complicated.) But there are five main factors that may be to blame if your jeans feel tighter these days.

The amount of lean muscle we have begins to decline by 3 to 8 percent per decade after age 30, a process called sarcopenia, described in a review published by the National Institutes of Health (NIH). You may also lose muscle if you’re less active because of age-related health conditions, such as arthritis, or if you’ve been sidelined with an injury or surgery for several days, Primack says. “All of these [factors] individually do not cause a significant decline, but cumulatively they surely do,” he says. Why does that loss of muscle matter? Because lean muscle burns more calories than fat, even at rest, according to the Mayo Clinic. Unless you’re regularly strength training with weights to maintain and build muscle, your body will need fewer calories each day. That makes weight gain likely if you continue to consume the same number of calories you did when you were younger. “Most people will not adjust calories,” explains Marcio Griebeler, MD, an endocrinologist at Cleveland Clinic in Ohio. “They keep eating the same amount, but because they have less muscle mass to burn those calories and less activity, they end up gaining weight over time.”

2. You’re Undergoing Normal Hormonal Changes

According to data from the National Center for Health Statistics, both men and women undergo changes in hormone levels that help explain why middle age is prime time for putting on pounds. For women, menopause — which tends to happen between ages 45 and 55, according to the National Institute on Aging — causes a significant drop in estrogen that encourages extra pounds to settle around the belly, explains Dr. Griebeler. This shift in fat storage may make the weight gain more noticeable and increase the risk of high blood pressure, heart disease, high cholesterol, and type 2 diabetes. In addition, Griebeler notes, fluctuations in estrogen levels during perimenopause, the years leading up to menopause, may cause fluctuations in mood that make it more difficult to stick to a healthy diet and exercise plan. As a result, the average weight gain during the transition to menopause is about five pounds, according to UC San Diego Health. Men, on the other hand, experience a significant drop in testosterone as they age. It begins to decline gradually around age 40 at a rate of about 1 to 2 percent per year, notes Harvard Health. Testosterone is responsible for, among other things, regulating fat distribution and muscle strength and mass. In other words, lower testosterone can make the body less effective at burning calories. The pituitary gland’s production of growth hormone (GH) also slows from middle age onward, per Harvard Health. One of GH’s many functions is to build and maintain muscle mass. So with less GH, it’s harder for your body to make and maintain muscle, which, in turn, also impacts how many calories you burn. “It’s a snowball effect,” Griebeler says. “You start accumulating more fat, have less lean body mass; you burn fewer calories, and that just keeps adding up over time."

3. Your Metabolism Is Slower Than Before

That decrease in muscle mass is likely to slow your metabolism, a complex process that converts food calories into energy, according to the Mayo Clinic. Having more fat and less muscle reduces calorie burning. Many people also become less active with age for various reasons, which further slows the number of calories you burn. Age isn’t the only thing that determines your metabolic rate, however — your body size and sex play a role. So do certain health conditions, such as hypothyroidism or Cushing’s syndrome, which become more prevalent with age as well.

4. You’re Busier With Work

By the time you’ve reached your forties and fifties, your career is likely in full swing — which is great, but brings its own weight loss challenges. For one thing, you may be moving less. You may commute an hour or so to and from work, sit at a desk for eight or more hours a day, and have so much on your plate that there’s no time to go for a walk or exercise during the workday. You may also find yourself too busy to break for lunch, increasing the odds that you’ll scarf down something from the vending machine or order in calorie-dense takeout food, notes Rachel Lustgarten, RD, a nutritionist at Weill Cornell Medicine and NewYork-Presbyterian Hospital in New York City. As for work-related stress, that can militate against a healthy weight, too. The stress hormone cortisol increases the level of the hormone ghrelin, which causes you to eat more, according to a systematic review and meta-analysis in the March 2021 Nutrients.

5. You’re Experiencing Major Lifestyle Changes

Some of the reasons for weight gain in middle age have nothing to do with what’s happening inside your body and everything to do with the way life changes as people enter their thirties and forties. One of the biggest changes comes when you start a family. Suddenly, the hour you spent at the gym after work is spent with your toddler at home. Later, your child’s after-school time is filled with playdates, homework, and other activities that require your attention. “You do not seem to have time anymore for yourself,” Primack says. As a result, your diet and exercise intentions might slip, causing a few pounds to creep on.

7 Science-Backed Ways to Battle the Bulge at Midlife and Beyond

Fear not! There are specific, effective tactics you can deploy to retake control of your weight.

1. Focus on Healthy Foods

Griebeler advises increasing your fruit and vegetable intake and decreasing the amount of fast food, added sugar, and other processed foods you consume. You’ll also want to prioritize whole foods — vegetables, beans, nuts, whole grains, and fruit — packed with fiber, says Lustgarten. “It will make it easier to control calories. These are high-volume foods — they take up more room in the stomach — and they generally contribute fewer calories to your daily intake,” she explains.

2. Downsize Your Portions

Learning to adapt your diet to your body’s lower calorie needs is a gradual process. Griebeler suggests you start by trimming 100 to 200 calories each day and adjust as needed from there. Using a calorie counting app is one way to monitor your food intake. You’d be surprised to see what a big difference such a small change can make.

3. Stay Well Hydrated

It’s easy to confuse the sensation of thirst for hunger. Stay hydrated with water (rather than with calorie-rich beverages like sodas, fancy coffee drinks, and fruit juices), and you’ll ramp up your metabolism, increasing the breakdown of fat, suggests a review of several animal studies published in Frontiers in Nutrition in June 2016.

4. Find Solutions for Taming Stress

For many people, stress leads to stress eating, Griebeler says. Do what you need to do to relax, whether it’s with a twice-weekly yoga class or short five-minute meditations throughout the day.

5. Give Your Major Muscle Groups a Workout

That loss of muscle mass you read about earlier? Fight back by adding strength training to your exercise routine. “You want to preserve muscle mass as much as possible,” Griebeler says. “With more muscle, you burn calories more efficiently and you’ll be more active because you have better balance and more stamina.” A good place to start is with the National Institute on Aging’s easy at-home strengthening Go4Life exercise program.

6. Move Your Body More

Try to incorporate a half hour a day of aerobic exercise — which is anything that gets your heart rate up, such as jogging, walking, biking, or swimming, advises Lustgarten. Can’t put together 30 minutes all at once? Break it up by doing three brisk 10-minute walks over the course of the day. “Short bursts of activity have a cumulative effect and count toward a daily exercise goal,” she says.

7. Get a Good Night’s Sleep

If you don’t wake up feeling energized, you’ll be less active during the day and will burn fewer calories as a result. Primack says to log somewhere between seven and nine hours of sleep per night.