(NaturalNews) While both aerobic exercise and resistance training will improve your overall health, only aerobic exercise is actually helpful in producing weight loss, according to a study conducted by researchers from Duke University and East Carolina University, and published in the Journal of Applied Physiology.
"Given our observations, it may be time to seriously reconsider the conventional wisdom that resistance training alone can lead to weight and fat loss," lead author Leslie H. Willis said.
The study was funded by the National Heart, Lung, and Blood Institute, a division of the National Institutes of Health.
Researchers assigned 234 sedentary adults between the ages of 18 and 70, all of them overweight or obese, to take part in one of three supervised exercise programs for eight months. The participants were assigned either to aerobic training, resistance training or a combination of the two.
Participants in the aerobic group exercised vigorously for approximately 45 minutes three times a week, raising their heart rates to between 70 and 85 percent of maximum. Participants in the resistance group performed three sets of eight to 12 repetitions on eight separate resistance machines three times per week, exercising all major muscle groups. The amount of resistance experienced increased over the course of the study, to compensate for the participants' increasing strength.
Participants in the combination group performed all the same exercises as participants in both the aerobic and resistance groups.
At both the beginning and end of the study, researchers measured each participant's weight, waist circumference, body composition, and cardiopulmonary fitness and strength. A total of 119 participants finished the study with complete data. The researchers believe that this makes the study the largest randomized trial of its kind.
Weight loss vs. muscle-building
The researchers found that while participants in both the aerobic and combination groups lost weight, participants in the resistance group actually gained weight, due to increase in lean body mass (which is more dense than fat). Likewise, both body fat percentage and waist circumference significantly decreased in both the aerobic and combination groups, while there was no change in the resistance training group.
Resistance training and combination training were both effective at increasing lean body mass, while aerobic exercise had no effect. Due to the combination of decreasing body fat mass and increasing lean body mass, a combination of aerobic and resistance training was by far the most effective method of decreasing body fat percentage.
According to Willis, the study has important implications for busy people who are seeking to improve their health with only a limited amount of time spent exercising each week.
"If increasing muscle mass and strength is a goal, then resistance training is required," Willis said. "However, the majority of Americans could experience health benefits due to weight and fat loss.
"The best option in that case, given limited time for exercise, is to focus on aerobic training. When you lose fat, it is likely you are losing visceral fat, which is known to be associated with cardiovascular and other health benefits."