Margaret Penfield of Thousand Oaks, California, had gotten into a vicious cycle of weight gain — eating late-night desserts and skipping exercise because of her hectic schedule.

Her menopause-induced depression may also have sapped some of her motivation.

But she wasn’t going to let the pendulum swing too far. She had always led an active lifestyle, and she decided to kick it up a notch.

Penfield started going to the gym three or four times a week, completing a one-hour routine of cardio and weight training. She changed up her cardio exercise to include activities like swimming and aerobics classes. She also went hiking once a week with a group of friends.

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In time, she lost about 35 pounds. But making these changes wasn’t easy. When she first started, she could barely do one push up.

“For the rest of my life, I’m going to be able to do 10 push ups,” she told LifeZette.

Penfield said the weight gain can really sneak up as the years go by. It’s hard to overcome the inertia of sedentary habits.

“You don’t realize how much weight you put on until you look back and see pictures,” she said.

Although Penfield’s weight loss success may not have been easy, it’s probably within reach for many women like her. A new study from the University of Massachusetts Amherst shows that physical exercise has a greater effect on body composition after menopause than it does before menopause.

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A total of 630 premenopausal and 274 postmenopausal women participated in the study, in which researchers tracked the amount of time they spent in both sedentary and physically strenuous activities.

Women who had undergone menopause spent more time in sedentary activities. And as expected, the greater the amount of sedentary time, the higher the body mass index (BMI) of the women.

However, this wasn’t true to the same extent in both groups.

“Across the board, for each measure of body composition, we found that light physical activity had a greater impact on postmenopausal compared to premenopausal women,” Lisa Troy, lead author of the study, said in a statement.

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“This is an important public health message because as women go through menopause, physiological changes may decrease a woman’s motivation to exercise. What we’ve found in our study suggests that doing even a little bit of exercise may make a big difference in body composition.”

Dr. JoAnn Pinkerton, executive director of the North American Menopause Society, said it’s typical for women to gain about 12 or 15 pounds during menopause because of hormone shifts. The body’s estrogen balance, which helps to control weight gain, is changing, and a decrease in testosterone can lead to less muscle mass, which lowers metabolism.

“Menopausal women are stressed,” Pinkerton told LifeZette. “They are taking care of teenage children and aging parents, and they may be in the middle of a busy career. They have less chance to exercise.” These factors can contribute to significant weight gain.

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While many women complain they are doing what they’ve always done and still gaining weight, Pinkerton said body changes during menopause necessitate a change in routine.

If you’re struggling with postmenopausal weight gain, Pinkerton suggests the following changes:

  • Eat your meals on a smaller plate, and fill half that plate with vegetables or a serving of salad (dressing on the side). The other half can be your entrée.
  • Find ways to add activity to your daily routine. Play active games with your grandchildren, or add walking to your day.
  • Start your day with a seven-minute routine that includes aerobic exercise such as jump rope, jumping jacks, or running in place. Then add sit-ups, push-ups, and weightlifting.
  • Make sure to wear comfortable shoes, especially if you haven’t led an active lifestyle before.
  • Find an exercise partner who can encourage you and keep you accountable.
  • Keep a journal to track your calories, and don’t eat processed foods. If you eat out, take half your serving home to eat later. Avoid excess alcohol.

Pinkerton says women who experience severe menopausal symptoms can find ways to get creative with their exercise. Warm water swimming, for example, can help with joint pain and can stretch muscles to make them more flexible.

For Penfield, at least, regular exercise helped to moderate some of the negative symptoms she was experiencing. “A sedentary lifestyle does not help with menopause,” she says. “The fact that I’m more active really helped me get through the symptoms of menopause.”