Think back to your teens and 20s. Were you an athlete? Did you easily maintain muscle while eating whatever you wanted?

Now snap back to the present. You’ve probably found that not only have you lost muscle mass, you’ve also gained weight.

No matter how physically active we are, men lose muscle mass as we age. Tack on responsibilities like work and family that leave little time for exercise, and men who were once athletic find a bulge has been slowly sneaking up on them.

So, where did all the muscle go? And can we get our bodies back to their heyday shape?

Take the Slow Route

Kevin Richardson, a New York City-based body builder and personal trainer, says the key to restoring your body to its glory days is a focus on weight training.

“There tends to be this idea with age that it’ll take longer and be a more arduous path back to being in great shape,” Richardson says.

“But muscles have memory. If you were in good shape at one time, you’re not necessarily starting from scratch. People at all ages respond well to weight training.”

For men who’ve decided to make fitness a priority again, Richardson urges them to get back into a routine gradually.

“One mistake people make is they try to do everything at once, and aim to work out exactly like they did 15 or 20 years ago,” he says. “Then they get hurt or discouraged and quit everything.

“If you train smart and build your strength back up with patience, there’s a good chance you could be right back out there with the younger guys.”

Don’t Overdo It

So you’re hitting the weight bench for the first time in a long time, and you’re worried you’ll be on it every day. Your initial instinct might be that more is better, but Richardson recommends engaging in weight training no more than three days per week.

“Get quality, not quantity,” Richardson said. “Think of the routines as regular things in your day like brushing your teeth.”

Weight training also can also help strengthen bones, more so than cardio-focused exercises, Richardson says.

“Getting older doesn’t have to equate to a reduction in physical ability,” Richardson says. “Look at (American world champion powerlifter) Fred Hatfield, who at age 45 squatted more than 1,000 pounds and broke a record. People shouldn’t underestimate what they can achieve later in life.”

Richardson recommends setting both short-term incremental goals in addition to longer-term fitness and weight loss signposts.

“Be patient and realistic about how much time it will take you to intelligently become fit again, but don’t be afraid of big goals either,” he says.

“If you aim too low, you might not realize your full potential. You could be the one breaking records in your 40s or even 50s.”