Its usually not just due to losing muscle mass over time (more on that later). "It's multifactorial," says Fatima Stanford, MD, MPH, obesity medicine physician scientist at Massachusetts General Hospital and Harvard Medical School. Numerous factors can sneak up on you and help you gain or hold onto weight, including your lifestyle, your food, your biology, and your sleep habits. The good news in that is that there are also numerous ways to tackle getting your weight to where you want ityou don't have to force yourself into one approach, and you get to choose what works for you.

Guys often wonder whether a dip in testosterone is at the root of their weight gain, says Dr. Stanford. "When men develop overweight and obesity, they tend to have a drop in testosterone that leads to a drop in energy and more retention of adipose tissue, she says. The excess adipose tissue drives testosterone down. But taking testosterone isnt usually the answer. Thats not the underlying problem. Once we normalize the weight, the testosterone normalizes," she explains.

Instead of looking to testosterone first, try these other, more effective strategies to hack your biology and lifestyle and lose weight after 40.

1) Dont force yourself to do the most popular plan

There are many eating patterns that can be used to lose weight, says William Samuel Yancy, M.D., director of the Duke Diet and Fitness Center and associate professor of medicine at Duke University. Many have evidence behind them, whether thats keto, Paleo, Mediterranean, vegan, or anything else. Interestingly, theres not as much research on what works for men as there is on women, but for men, sometimes its as simple as shortening the time in which you are eating to an 8- to 10-hour window a day, says Kristin Kirkpatrick, R.D.N., consultant for Integrative and Lifestyle Medicine for the Cleveland Clinic. Even something as straightforward as not eating after 6 PM can make a big differenceone of her male clients who lost 150 pounds found that to be especially helpful, she says.

If you prefer a specific plan with specific rules, make sure it goes with your lifestyle, which, for most guys, gets increasingly complicated in your 40s with more responsibilities at work, with your family, and maybe even with your aging parents. A vegan diet can be hard to do in a healthy way if you live a grab-and-go existence. Meal prep is going to be a challenge if youre never home long enough to cook. Dont just pick what worked for a friend; pick whats likely to work with your busy, over-40 lifestyle.

Dr. Stanford is emphatic that you need to be sure that the eating style you choose to lose weight after 40 is something you can do for the rest of your life. "If it's not something you can sustain for the next 20 or 50 years, then why are you doing this at all?," she points out.

For a sustainable plan, "I don't like to hyperfocus on calories. It's important to have a high-quality diet of lean protein, whole grains, and fruits and vegetables," Dr. Stanford says. "Processed foods lead to weight gain, so the less processed the food you eat, the better." And the more satisfied you could end up being. Her example: A nice meal of salmon plus some grains and a vegetable and a salad can give you a lot more volume than a Shake Shack stop would, and would give you more of a sense of being full afterward. When it comes to the high-quality diet she advocates, "nothing is bizarrewe know that lean protein, whole grains, fruits, and vegetables are constant no matter how the guidelines for healthy eating have changed over the years," she says.

2) Get stronger

Starting in your 30s, you can lose three to five percent of your muscle mass each decade if you dont stay active. Note the last part of that point: If you dont stay active. As you get older, "there's a lot of competition for your time and energy," says Dr. Yancy. For some men, that can push exercise out of the picture. But it doesn't take heroic efforts to put it back into your life.

You can maintain that muscle or regain it with a regular strength routinemeaning you do moves that hit the major muscles of the body at least twice a week. A great place to start: This 3-Week Full-Body Workout Plan for Men Over 40 .

Why thats so important: The more muscle we have, the more calories we burn, Kirkpatrick says. Even if it doesn't actually help you lose weight, it can help keep you from gaining italong with all the other good things it does for your body, mind, and life. Lots of over-40 guys like HIIT, since its compressed timeframe ends up having a low impact on your schedule.

That doesnt mean you should only strength train; aerobic activity is helpful, too. But supplementing your Spin/run/row/elliptical routine with strength training is essential.

3) Check your medications

Sometimes the medicines you're taking for other issues, such as high blood pressure and antidepressant meds, can increase your weight or keep you from losing it, says Dr. Stanford. Ask your doctor if your weight concerns could be side effects of the prescriptions you're getting filled. Often, there are other formulations that can be effective but wouldn't have those side effects for you.

4) Make sure you're sleeping well

Sleeping enough is important, and if your lifestyle is making you cheat sleep, then think about what you can do to get enough. Sometimes, however, biology is keeping you from enough shuteye, and it's imperative to solve that. "Untreated obstructive sleep apnea can lead to additional weight gain," says Dr. Stanford. If you are making all the right efforts to get restorative sleep and still don't feel restored, consider seeing a sleep doctor, who can drill down on the problem and help you find some solutions.

5) Be sober curious

Another factor I see that can help men is to take a look at drinking habits, Kirkpatrick says. Men that I counsel who cut alcohol or significantly cut back tend to lose weight more easily.

Now that the whole sober curious moment is making not drinking trendy, its easier to find alcohol-free options. Less alcohol not only means youre drinking fewer calories, it can also mean fewer late-night bowls of ramen or plates of double cheeseburgers on the way home from happy hour. Today, its also easier to maintain a social life when youre not overdrinking, since theres the new perception that youre not saying no to a beer or five; youre part of a movement.