As spring rolls in with summer not far behind, people of all ages begin to get serious about their fitness goals and getting in shape. But what exactly does being “in shape” mean? The answer is complex and depends on who you ask.

“Being in shape can mean different things depending on the context,” says Asad Siddiqi, D.O., chief of rehabilitation medicine at New York Presbyterian-Brooklyn Methodist Hospital in New York City. There is no one-size-fits-all definition.

Still, experts typically agree that the concept boils down to maintaining a healthy weight, exercising regularly, and receiving adequate nutrition through a balanced diet. “To me, being in shape means a person has the physical strength and flexibility to accomplish daily tasks and enjoys a fulfilling life,” adds Siddiqi.

Exercise to stay in shape

The American College of Sports and Medicine guidelines recommend adults get 150 minutes of moderate-intensity weekly activity. Moving your body is vital to staying in shape, but most adults fall short. According to an older study by the Centers for Disease Control and Prevention, only 28% of Americans are physically active, and that activity level steadily declines with age. Siddiqi says it’s never too late to start moving and that doing anything is better than nothing. “Think about exercise as an investment,” says Siddiqi, “not just for our health today, but for the rest of our life.”

Eating healthfully

Aside from moving your body, experts say maintaining a good diet is crucial for getting—and staying—in shape. “The first step is healthy eating,” says registered dietitian nutritionist Ruth Frechman, owner of On the Weigh, a private practice that specializes in weight loss and nutrition education in Los Angeles. To ensure a balanced diet, Frechman advises clients of all ages and genders to visually divide their plate into quarters: one quarter should be protein, one quarter should be carbs, and the rest should be vegetables. This food combo gives you energy and contains the vitamins and nutrients your body needs to function.

Aside from these basics, the following tips will help you look and feel your best in every decade.

How to stay in shape in your 30s

Around your third decade, you may notice your favorite jeans may fit a little differently, and you’re less flexible than you were in your 20s. This is likely due to an increase in body fat and a loss of muscle mass. In addition to establishing an exercise and nutrition regimen to help keep your body strong, you should focus on chronic condition prevention.

Frechman also recommends staying on top of your blood work to ensure nutrient levels, and heart, thyroid, and kidneys are in good standing. Frenchman also recommends staying within your body mass index (BMI) range when managing your weight. Though BMI has recently been criticized as an inaccurate tool, Frenchman says “I’m a believer in BMI because extra weight causes inflammation, which can lead to early health conditions, like diabetes and high cholesterol.”

How to stay in shape in your 40s

Your 40s are when hormone and strength levels decrease, and health conditions, like osteoarthritis may and high blood pressure may arise. To nip aliments in the bud, your wellness routine should be customized to address your specific health concerns, advises Siddiqi. “Maybe you’ve noticed that your cholesterol or blood sugar is a little high, you’ll need to adjust to a type of exercise and diet that might help reduce it,” he says.

How to stay in shape in your 50s

Your 50s are a prime time for getting in shape because you’re setting the stage for your second half of life. Your metabolism begins to slow down at this age, women start to experience menopause, and bones may become more fragile. Siddiqi suggests focusing on a fitness routine that improves balance and strength, he recommends workouts like Tai Chi.

To make up for a slower metabolism, Frechman advises eating smaller meals. She also suggests talking to your doctor about which dietary supplements you may need if you aren’t getting adequate nutrition from your food. Some people have a decrease in minerals like calcium as they age, which is necessary for strong bones.

But Frenchman’s most important advice is appropriate for all ages: “Enjoy life and do what makes you happy.”