Losing weight may never feel easy, but it also never gets easier. Fitbit users ask all the time—is it harder to lose weight as you get older? Is it impossible? Is there anything else you can do? “Yes, it’s definitely more difficult to lose weight as you get older,” says Kim Larson, registered dietitian and spokesperson for the Academy of Nutrition & Dietetics. “There are so many physiological changes as you age, through your 30s, 40s, and 50s. Most people think of middle age and menopause as the big moment, but there’s more to it than that.” To start, here are three major factors.

• Muscle loss: Starting in your 30s, you lose as much as 3 to 5 percent of your muscle mass

  per decade. Lean muscle burns more calories, so the less muscle you have, the fewer calories you burn.

• Metabolism slows: As you lose muscle, your metabolism slows down. You simply need fewer calories as you get older, and excess calories accumulate as fat. Plus, if you’ve done any yo-yo dieting in your day, you may have slowed down your metabolism more.

• Hormonal changes: For women, the hormonal changes leading up to menopause contribute to weight gain. As your body loses estrogen, it becomes much more efficient at storing fat, particularly belly fat. Body composition is definitely different for women and men. But for men, testosterone also decreases as you get older, and body fat increases.

But also, life happens! There’s a lot more context that contributes to slow and steady weight gain over the years, which Larson sees in her clients and practice every day. Here’s how to think about it by decade. Plus, what you can do to stay fit at every age.

“Your 30s are an awesome time,” says Larson. “This is the decade you want to get and stay physically fit, and focus on maintaining.” In your 20s, you could binge on pizza and wine and work it off quickly, but in your 30s, it takes a little longer. As your muscle mass and metabolism dip, you lose the margin for error. You’re also leaning into your career, experiencing more stress. And women are having babies, losing sleep, and get into irregular eating patterns. “Don’t wait to lose the baby weight,” says Larson. “You don’t want to take 5 to 10 pounds with you into the next decade.”

“The 40s are a prevention decade,” says Larsen. “It’s time to get on track and stay there.” If those babies are now big kids, and you’re juggling commuting and carpools, it’s easy to slip into sedentary habits. “I see a lot of people let themselves go,” says Larson. “I’m honest with my clients. You do not want to go into middle age or menopause overweight. Because you will not know what hit you. Eat well, stay active, and practice healthy habits as a family.”

“The 50s come as a shock to many people,” warns Larson. “People who have never had trouble losing or maintaining their weight suddenly find it’s a real struggle.” You might have better life balance at this point, but your body is downshifting to a different gear, and getting super efficient at storing fat. “That doesn’t mean you give up, now or ever!” says Larson. “But you have to adjust your mindset, expect changes to come slowly, and set a new weight goal.” Larson recommends tapping up your activity and reducing your calories by 300 to 400 per day, in order to maintain.

“There is no miracle pill for weight loss or aging,” says Larson. “You have to go back to basics: Eat well and exercise every day.” Specifically, there are a few key things you can do, to keep your metabolism burning bright across your whole life.

• Strength training is the best way to maintain your muscle mass and body composition. Women should be doing it. Everyone should be doing it. So find workouts you love that make you feel strong.

• Protein becomes even more important as you get older, to build muscles and manage your hunger. Larson recommends 1 to 1.5 grams of protein per kilogram of bodyweight.  Spread it throughout the day, hitting at least 20 to 25 grams of protein at breakfast.

• Calories have to come down, even if you’re active, even if you’re eating healthy foods. Do the math on how many calories you really need, and try food logging for a few weeks, to figure out where calories are sneaking into your diet and ways you can easily cut back.

Frustrating? Of course. Impossible? Hopefully not. “You just need to be a little more savvy and prepared,” says Larson. “Be in the best physical and mental health possible right now, so you can move gracefully into the next decade of your life.” Most important, maintaining a healthy weight helps you avoid scary diseases, so you can enjoy a long and happy life—and play with your grandkids.