When it comes to staying slim, cardio exercise tends to get most of the attention. The good news is that you may not need to log endless hours running to keep your waistline from expanding. In fact, research from Harvard University suggests weight lifting could be the most effective way to keep trim around the middle – but don’t discount cardio’s benefits.

In a 2015 study published in Obesity, researchers examined exercise habits and waist sizes of 10,500 healthy men enrolled in the Health Professionals Follow-Up Study (a survey of male health professionals that has provided information for over 100 published research papers). Over a period of 12 years, participants received biennial questionnaires about their overall health including questions about their physical activity, such as time spent lifting weights and doing aerobic exercise. They also measured their waistlines.

Survey results showed men who increased their weight training by 20 minutes per day had a smaller age-related increase in waist circumference than men who spent an increased 20 minutes on moderate-to-vigorous aerobic exercise. However, weight training did not help in losing body weight, and in some cases even resulted in slight weight gain, likely due to increases in muscle mass. Adding moderate-to-vigorous aerobic exercise each day was most strongly linked to less body weight gain over the 12-year period.

Researchers suggest a combination of weight training and aerobic activity is the key to the greatest health benefits and body composition change.  Weight training promotes muscle growth, while shedding fat mass, thereby increasing metabolic rate and decreasing abdominal fat. Adding cardio exercise like jogging or biking to the routine helps to shed pounds and may provide health benefits like improved immunity, brain power, and heart health.

The CDC recommends adults get 150 minutes of moderate aerobic activity per week, plus two or more days of strength training that work all the major muscle groups. If you’re just starting out with exercise, try walking for 30 minutes, five days per week, and adding strength training to the mix on two days. No weights? No problem! Pushups, yoga, and even heavy gardening count as strength training, as long as you feel the burn!

Published April 1, 2015