January 4, 2013
John DiTraglia MD
There are two kinds of exercise, aerobic and resistance training. Aerobic exercise is running, or swimming or cycling and exercises your heart and lungs mainly, and most of the big the muscles of the body more or less simultaneously.
Resistance training is also known as strength training or isometric exercise or body building. This type of exercise is sit-ups or push ups or weight lifting and exercises just more specific muscle groups with the aim of increasing their individual size.
There is another thing called anaerobic exercise or interval training that happens when you exercise intensively to the point that you exceed oxygen delivery to the muscles and this leads to rapid fatigue. This may have certain different benefits too but that’s a discussion for another day.
Which method would be best for weight loss? This week there was an article examining this question. (1) These investigators from Duke University got 119 sedentary, overweight or obese adults and put them through one of three exercise protocols for eight months:
Resistance training (RT), aerobic training (AT) and combined training with both (RT/AT). The combined resistance training-aerobic training group spent twice as long exercising. They found that the AT and AT/RT groups reduced total body mass and fat mass more that RT but they were not different from each other. RT and AT/RT increased the muscle mass more than AT as expected. So while RT did nothing to the fat mass it decreased the fat mass to lean body mass ratio because it made bigger muscles. They conclude that, “Balancing time commitments against health benefits,… aerobic training is the optimal mode of exercise for reducing fat mass and body mass.”…Unless you want to build up muscles.
Remember, we have said that exercise isn’t worth much when it comes to weight loss. So lets look closer at the details provided by this project. The aerobic training involved the equivalent of running 12 miles a week at 65 to 80 percent of peak ability. This group lost about four pounds out of 194 pounds or about 2 percent. Most of that, but not all was fat, and their waist circumference decreased a little less than half inch.
They measured total fat in the body and the AT group lost 4 percent of that. The combined RT/AT group lost about the same total weight but since they also built up some muscle, more of that weight loss was fat, actually twice as much and their waist circumference decreased a little more than half inch and almost seven percent of their total fat. Not a lot but something and it almost makes doing twice as much exercise by including resistance training seem worthwhile. Again the resistance training alone group gained some muscle and a little weight and didn’t lose any significant fat or waist circumference.
Caloric intake was monitored but not restricted and did not change during the exercise period for any group. It sounds like their bodies just got more efficient since exercise didn’t make them eat more.
Willis LM et al. Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults. J of Applied Physiol. December 15, 2012;113(12):1831-7.