Soy protein – with isoflavones – helps training women slim faster

If you ignore bonus doses of saturated fat, dioxins, hormones and antibiotics, animal protein can be very nutritious. Too bad ‘from October 31’ there will be 7 billion of us – and science shows that many people can’t all be dining on beef. That’s why here on we try to prove a very simple point: plant proteins consist of amino acids too – and it is a myth ‘these go without the essential ones.’

Soy protein isoflavones help women slimWhen however you dig through the piles of plant protein research you soon end up entangled in the soy debate. Here too, it proves, myths exist and myths can be busted. Meanwhile we discover other stuff we can’t keep from you.

Strength training for weight loss

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.

Brazilian researchers have now discovered you can strengthen that effect by including 25 g extra soy protein in your diet.

The 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.

Soy protein helps training achieve weight loss

The soy workout

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 soy 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.

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.

Increased metabolism

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.

Soy protein helps training achieve weight loss

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.

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 soy protein.

Soy isoflavones? Or mere protein?

The study [PDF] 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 soy industry is one of the most important sectors of the economy in Sao Paulo.

© Willem Koert |

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