By: Ergolog

Even if you only do a very small amount of weight training you increase your fat burning – not while you’re training, but when you rest. American sports scientists have shown this for the first time in a study on the long-term effects of weight training. The results of their research have been published in Medicine & Science in Sports & Exercise.

The researchers did a trial with forty fat men and women. The experiment lasted six months. Half of the test subjects did nothing, and the other half trained three times a week in a gym. During each training session the test subjects completed a minimal training programme, which did cover all the important muscle groups.

Each training session consisted of nine exercises – chest press, back extension, lateral pull-down, triceps extension, shoulder press, leg press, calf raise, leg curl, and abdominal crunch. The weight used was set at 85 percent of the weight at which the test subjects could perform just one rep. The subjects did three to six reps. Whenever they managed to do more than six reps, the supervisors increased the weight.

The table below shows the effect of the programme on the body composition of the test subjects. C = control group, RT = resistance training.

The minimal training programme didn’t stop these fat people from becoming fatter. But the increase in the fat mass and the percentage of body fat in the resistance training group was smaller than in the control group.

Before and after the programme the researchers shut the test subjects up in a room calorimeter for one day. This enabled the researchers to check the test subjects’ excretions and to measure what they breathed in and out. This way they could measure exactly how much energy the test subjects used. The figure below shows the effect on the resting metabolic rate (the amount of energy you expend when you’re doing absolutely nothing) and the sleeping metabolic rate (the amount of energy you use when you sleep).

It’s the fat burning that goes up as a result of doing weight training, even though the effect is not statistically significant. The researchers believe that something went wrong during the first measuring session, before the experiment started. The test subjects probably consumed less energy than they used up.

The Americans did not study how weight training increases energy expenditure exactly. They do have a few ideas though. Weight training leads to an increase in production and breakdown of muscle protein, and that costs energy. That’s one theory.

Another is that the training leads to increased activity of hormones such as adrenalin and noradrenalin. These stimulate the fat cells to release their content into the circulatory system and raise the energy burning in the tissues. That’s a second theory.

“The minimal resistance training protocol described in this study may provide an attractive alternative to either aerobic exercise or multiple-set resistance training programs for weight management in busy young adults, owing to the minimal time commitment (11 min per session) and the fact that participants did not need to change clothes or shower”,

the researchers write. In conclusion they say that in studies with a higher training volume – and probably with more test subjects – they’ll see stronger effects.

source: Med Sci Sports Exerc. 2009 May;41(5):1122-9.