Weight training for 20 minutes per day helped healthy men stave off age-related abdominal fat gain better than engaging in aerobic activities for the same amount of time, according to research published in Obesity.

The study examined prospectively whether weight training, moderate to vigorous aerobic activity (MVAA), and replacement of one activity for another were associated with favorable changes in WC and body weight (BW).

Physical activity, waist circumference and body weight were reported in 1996 and 2008 in a cohort of 10,500 healthy U.S. men in the Health Professionals Follow-up Study.

With adjustments for potential confounders, an inverse dose-response relationship was seen between weight training and waist circumference change. Less age-associated waist circumference increase was seen when activity was increased 20 minutes per day; the benefit was stronger for weight training than for moderate to vigorous aerobic activity, other activities or television watching.

The strongest inverse association with waist circumference change was seen when weight training for 20 minutes per day was substituted for any other discretionary activity. Moderate to vigorous aerobic activity showed the strongest inverse association with body weight change.

“Incorporating weight training with aerobic exercise is crucial to maintain a healthy waistline,” Rania Mekary, PhD, of the Department of Nutrition at Harvard said. “Further studies are needed among women, older men, and other ethnic groups to compare the frequency and volume of weight training on waist circumference change.” Combining weight training and aerobic activity, which is particularly beneficial for heart health, would be optimal, researchers said. "When we age, we lose muscle mass and we tend to accumulate more body fat. If you only engage in aerobic activities, such as running, jogging, you will end up losing fat, as well as muscle mass," said study co-author Rania Mekary, a researcher at Harvard School of Public Health. "That's why you need to supplement your workout with resistance training, in order to preserve the muscle mass." However, that is not to say that aerobic activities are less important for health, Mekary emphasized. Doing cardio exercises could help prevent conditions such as diabetes, heart disease and even cancer, she said.

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