Lose Weight in Your 20s, 30s, 40s

A decade-by-decade guide to staying fit

Your 20s

First, the good news. You’re burning more calories than ever. Why? During your 20s, you have more lean muscle mass than at any other time in your life, and a pound of muscle uses up roughly 147 more calories than a pound of fat does. Pregnancy can change all that. If you gain more than the recommended 25 to 35 pounds, the extra weight can pose a long-term obesity risk.

Weight-loss Rx for your 20s

Invest in your health by exchanging bad habits with good ones. “Your 20s should be about setting up your life for the next 60 years,” says Cathy Nonas, RD, author of Outwit Your Weight. Make half your plate fruits and vegetables. While you’re at it, cut down on red meat and junk food and boost your intake of whole grains. Eating a plant-based diet is one of the best ways to fill up on fewer calories: Fruits and veggies supply fiber and reduce your risk of a number of age-related diseases.

Lift weights. Strength training offsets the effect of a sedentary job and maximizes your body’s natural calorie-burning power by building muscle. “Work out with weights at least twice a week,” suggests C.C. Cunningham, spokesperson for the American Council on Exercise. Choose a weight that fatigues your muscles after 12 repetitions, and strive for one set of 8 to 12 reps for each of the eight major muscle groups (shoulders, chest, arms, back, outer thighs, inner thighs, butt and abs).

Fit in mini workouts. Do what you can around your home or office, using your own body weight as resistance: say, 30 squats in your cubicle or 30 raised pushups on the edge of your desk. Take the stairs instead of the elevator whenever possible.

Get more calcium. To stave off osteoporosis and stay slim, get 1,000 milligrams of calcium a day from low-fat dairy products, calcium supplements or a combination of the two.

Your 30s

Your 30s are prime time for putting on the pounds. Unless you were lifting weights throughout your 20s, you’re naturally starting to lose muscle — and gain fat — at a rate of about 2 percent per decade, especially if you have a relatively sedentary lifestyle. This subtle muscle-to-fat ratio change makes it tougher to maintain your ideal weight. As your muscle mass shrinks, your calorie requirement decreases.

Weight-loss Rx for your 30s

Now’s the time to regroup and rediscover yourself and your needs. What’s more, setting a good example is especially important when you’ve got others following your lead. “Women set the pace for healthy eating in a family,” says Nonas.

Make exercise a daily priority. Getting to the gym can be tough, so it’s important to find ways to be active throughout the day. Join in on the kids’ games. Walk everywhere. Mow the lawn. Do anything you can to get your heart rate up for about two and a half hours each week.

Know your body mass index. A BMI over 25 is considered overweight; a BMI over 30 is obese. Both classifications can up your risk of cancer, heart disease and type 2 diabetes. To calculate your BMI, log on to Nhlbisupport.com/bmi. Or multiply your weight in pounds by 705, divide the result by your height in inches, then divide that result by your height in inches again.

Stock your pantry. Make sure you always have healthy food on hand — whole-grain bread, fruits, veggies, low-fat dairy products. You’ll be less prone to order takeout on busy nights, which can increase your calorie load and downgrade your diet’s nutritional value.

Don’t skip meals. It only leaves you vulnerable to cravings. “When you’re on the run, a balanced meal-replacement shake or bar is definitely better than fast food,” says Nonas.

Your 40s

Your self-esteem is at its peak — and so it should be. You’re more accepting of the body flaws that drove you nuts in your 20s, and you’re probably pretty happy with the direction your life has taken. However, you’re still losing metabolism-boosting muscle mass, only now it’s at a rate of 5 percent per decade. And perimenopause, the 8- to 10-year period before menopause, may be settling in. With it comes declining estrogen levels and, possibly, mild depression that can be linked to weight gain

Weight-loss Rx for your 40s

Don’t accept the inevitability of mid-life weight gain. Keep your heart rate up. Moderate aerobic exercise — 30 to 60 minutes most days of the week — is crucial for offsetting your body’s natural metabolism decline. It can also prevent the depression that may accompany perimenopause.

Build muscle. If you haven’t begun strength training yet, start now. It will help preserve the muscle you have and build even more. To learn proper technique (and avoid the risk of injury), invest in a couple of sessions with a personal trainer.

Protect against soreness. You’re more vulnerable to everyday aches and pains, so don’t push yourself too hard. Gradually work up to a challenging routine. If you haven’t already done so, boost your intake of protein and antioxidant-rich fruits and vegetables; the nutrients will promote muscle repair and ward off soreness by destroying free radicals formed during exercise.

Take aim at osteoporosis. If you haven’t been strengthtraining or eating a calcium-rich diet throughout your 20s and 30s, you may be at risk of developing this condition. Start a strength-training program — and take 500 milligrams of calcium supplements three times daily — to help prevent further bone loss.

Sandra Gordon is freelance writer.