Some middle-age spread may be inevitable, but younger adults — especially women — can keep it to a minimum if they exercise consistently in their 20s, 30s and 40s, suggests a new study published Tuesday in the Journal of the American Medical Association (JAMA).
More specifically, the study found that moderate to vigorous exercise during the transition from young adulthood into middle age was associated with both smaller weight gains and smaller waistlines.
That waistline finding is especially important given that excess abdominal fat is now believed to be associated — even more, perhaps, than overall weight — with an increased risk of developing diabetes, heart disease and other chronic ailments that often strike at middle age.
Yes, a link between exercise and the battle of the bulge may seem obvious. But, surprisingly, there hasn’t been that much research into whether exercise can prevent long-term weight gain, said Pamela Schreiner, one of the study’s co-authors and a professor of epidemiology and community health at the University of Minnesota’s School of Public Health, in a phone interview. Most previous studies, she said, had people exercising for short periods of time and tended to focus on losing weight — not on preventing weight gain.
“This study has the benefit of being generalizable to a large group of people,” said Schreiner.
And the years leading up to middle age, she added, is when people are at highest risk of putting on the pounds.
The highs versus the lows
The study followed more than 3,500 men and women (aged 18 to 30 at the start of the study) for more than 20 years. Participants were divided into three groups, depending on an intricate scoring of their habitual activity levels. Most of the participants gained some weight over the two decades, but those in the highest activity level group gained much less than those in the lowest group — an average of 5.7 fewer pounds for the men and a stunning 13.4 fewer pounds for the women.
Their waistlines also stayed trimmer. When compared to their low-activity peers, the men in the high-activity group gained an average of 1.2 fewer inches in waist circumference and the women an average of 1.5 fewer inches.
These findings held even after the researchers adjusted for age, education, race, smoking status, alcohol use, calorie intake — and body weight. People who started the study overweight but who exercised with consistent vigor tended to gain less weight as they approached middle age than their overweight peers with more sedentary habits.
The one factor that did make a difference was gender. Women appeared to benefit the most from staying physically active, even though they tended to report less strenuous exercise patterns. Schreiner and her colleagues believe the difference may be because men may eat more food than women do when they exercise a lot. Another possibility is that the men are over-reporting their exercise habits.
A doable level of activity
High activity was defined in the study as about one hour of exercise per day for men and about 30 minutes per day for women.
But you don’t have to adopt those levels to keep your weight in check. The study found that even following current government guidelines — 30 minutes of moderate-intensity aerobic activity (brisk walking) five days a week — helped people keep their weight down as they approached middle age, although more modestly.
But you must stick with your exercise program, week after week, month after month, year after year. “If you don’t incorporate exercise into your lifestyle in a consistent manner,” said Schreiner, “you aren’t going to get the benefits.”
That, of course, is hard to do. In this study, less than 12 percent of participants maintained a high level of physical activity over the years.
Waiting too long to get started is also problematic. Other research has shown that even at the high-activity levels in this study (60 minutes daily for men and 30 minutes daily for women), people who are already middle-aged will struggle to keep excess weight off.
“At older ages,” Schreiner and her colleagues note in the JAMA article, “higher activity levels may be necessary to overcome the well-documented age-related declines in resting metabolic rate and lean body mass.”
You’ll have to cut calories, too.
In fact, Schreiner and the study’s other authors caution that even among young adults, “higher activity alone may not be sufficient to entirely prevent age-related weight gain.” (Again, most of the participants in this study gained some amount of weight over the two decades.)
“No studies have shown that over longer periods of time exercise alone will prevent weight gain, even in marathon runners,” said Schreiner. “You have to do other things, including being deliberate about your diet.”