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28.07.2011

Strength training + soya protein shake help women slim faster

Strength training is a great way to achieve a healthy weight, if you're prepared to take a long-term approach. Each pound of muscle mass gained leads to a rise in the amount of calories your body burns each day. You can strengthen that effect by including 25 g extra soya protein in your diet, Brazilian researchers discovered.

Study
The Brazilian researchers did an experiment with 60 women aged between 36 and 71. All had a BMI higher than 25, so they were overweight and had too little muscle mass. They were also all in the menopause. The researchers wanted to know if they could help the women to reach a healthier weight by getting them to do weight training and giving them a soya protein supplement. The experiment lasted for over three years: 160 weeks to be precise.

Some of the women trained three times a week in the gym, and each session lasted 90 minutes. They did 10 basic exercises with 60-80 percent of the weight at which they could just manage 1 rep. The work out was simple but thorough. The women did leg presses, leg extensions, leg curls, bench presses, pec-deck flies, seated rows, lat pulldowns, triceps pushdowns, barbell curls and crunches. They did three sets of each exercise and each exercise started with a warming-up and ended with a stretch cool down.

The protein shake contained 25 g soya protein and 50 mg isoflavones: 32 mg genistein, 15 mg daidzein and 3 mg glycitein.

Results
The researchers divided their subjects into 4 groups. G1 = strength training + protein shake; G2 = strength training; G3 = protein shake; G4 = nothing at all. G1 and G2 built up more muscle mass during the experiment.

	G1	G2	G3	G4
Increase in muscle mass	7%*	10%*	2%	0%
Estimated increase in muscle mass	1.33 kg	2.02 kg	0.39 kg	0.00 kg
Change in REE	+158 kcal/dag	+110 kcal/dag	-29 kcal/day (+/-)	-57 kcal/day (+/-)
* Statistically significant difference with G4

The protein shake did not boost the increase in muscle mass, but it did boost energy expenditure while resting [REE].

The researchers measured the subjects' REE before and after the 160 weeks. At the time that measurements were taken, the women hadn't eaten for at least 12 hours and hadn't trained for 24 hours. The figure below shows that the G1 group used up 17 percent more calories when resting than the G0 group did. That's the equivalent of 158 calories daily. In the G2 group the increase was 9 percent – which amounts to 110 calories more per day.

So doing a quick calculation: in the G1 group, one kilogram extra of muscle mass increased the daily calorie burning at rest by 119 calories. In the G2 group, one kilogram extra of muscle mass increased the daily calorie burning at rest by 54 calories. This is a calculation that would make scientists shudder, but it gives an idea.

Conclusion
Muscle tissue has a high rate of metabolism. The mitochondria in muscle cells produce heat continuously, and muscle tissue is constantly replacing itself. This costs energy, and the process seems to speed up a bit if you consume a little extra soya protein.

The study did not examine any other types of protein. The researchers believe however that the energy expenditure boost is caused by the isoflavones. These stimulate the energy production, according to the researchers.

The research was funded by the state of Sao Paulo. The soya industry is one of the most important sectors of the economy in Sao Paulo.

Source:
Rev Assoc Med Bras 2010; 56(5): 572-8.

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