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13.02.2011

Study: low carb + strength training = big fat loss, no lean body mass loss

Researchers at the Norwegian School of Sport Sciences have good and bad news for the fans of a low-carb diet for strength athletes. If you get inexperienced women to do weight training and put them on a low-carb diet at the same time, then their fat loss is dramatic [good], but the lean body mass gain is nil [bad].

Study
The Norwegians did an experiment on a small group of 16 fat women aged between 20 and 40. Half of the women continued to eat 'normally'. The other half was put on a ketogenic diet, following a diet in a book popular in Norway: Slank med ketolysekuren: en enklere vei til et lettere liv. The women were allowed to eat as much as they wanted, but their carb intake was restricted.

All the women – the low-carb dieters and the women whose diet had not changed – started doing weight training and did a workout lasting 60-100 minutes twice a week.

Each training session started with a 10-minute warming up on a cardio machine. After that the women trained all important muscle groups doing basic exercises like leg press, leg extensions, leg curls, chest press, rows, shoulder press, pull downs and biceps curls.

For the first 5 weeks the women used weights for which they could just manage 12 reps. After that the weight was increased, and they did sets of 8 reps.

Results
At the end of the 10 weeks, the women who had followed a low-carb diet [Lc=Ex] had lost 5.6 kg. Of that, 5.6 kg was fat. There had been no increase in lean body mass.

The women who had not changed their diet [Ex] had gained 1.6 kg lean body mass and lost 0.6 kg fat.

The figure below shows the amount of oxygen that the test subjects needed for each of the four different protocols to undertake the exertion. As you can see, the intensive exertion raised the energy burned during the moderate exertion. The shorter the resting period, the greater the effect.

If you look at the individual response of the women in the figure above, you'll see that some of the women did build up lean body mass on a low-carb diet. One actually lost 8 kg fat and built up 3.5 kg lean body mass. That's pretty good going in 10 weeks. But this was a 'best responder'.

The researchers found no remarkable changes in cholesterol or triglyceride concentrations in the women's blood.

Conclusion
"Resistance exercise performed twice weekly in overweight women on a low carbohydrate ketogenic may reduce body fat without significantly changing lean body mass, while resistance exercise on a regular diet may increase lean body mass in without significantly affecting fat mass", the researchers conclude.

The low-carb diet used in the experiment is a pretty extreme one. Strength athletes often reduce their carb intake during the day, but then eat controlled amounts of carbs just before, during and after a training session. Training stimulates muscle cells to absorb more glucose from the blood.

And a second point: a high-protein, low-carb diet fills you up, which also shows up in this study. The women in the low-carb group ate 1755 calories a day; the women in the other group ate 1972 calories. That's a difference of 217 calories. Is that why the women in the low-carb group didn't build up any lean body mass? Maybe they just didn't consume enough energy to do so?

Source:
Nutr Metab (Lond). 2010 Mar 2; 7:17.

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