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Crash diet works better without carbs

You need to lose a couple of kilos in a few weeks. The only solution: a strict diet with fewer than a thousand calories a day. You're guaranteed to lose fat - but unfortunately you'll lose muscle too. Italian researchers wrote in the European Review for Medical and Pharmacological Sciences that they have found a way to limit muscle loss during a crash diet: avoid carbs and replace them with protein.

The researchers got 18 healthy but overweight participants to go on a very strict diet for 3 weeks, consuming about 700-800 calories per day.

Nine participants were put on a more or less traditional diet: the energy was derived for 35-40 percent from fat, 15-20 percent from carbohydrates and the remaining 40-50 percent from protein. The participants consumed about one gram of protein per kilo bodyweight daily.

The other nine participants were put on a low-carb diet, where the energy was derived for 35-40 percent from fat, 5 percent from carbohydrates and the remaining 55-60 percent from protein. Half of the protein was given in the form of a whey supplement. The participants consumed about 1.4 gram of protein per kilo bodyweight daily.

The figure below shows the effects of the traditional crash diet.

Crash diet works better without carbs

Crash diet works better without carbs

The figure above shows the effect of the low-carb crash diet.

The figure below compares the results of the traditional diet and the low-carb crash diet. As you can see, the low-carb diet protected the muscle mass from breakdown. Both types of diet resulted in approximately the same amount of fat loss.

Click on the figure for a larger version.

Crash diet works better without carbs

The researchers' findings did not enable them to work out how a low-carb crash diet protects muscle mass against breakdown. They suggest that the combination of proteins and the lack of carbohydrates may lead to an increase in the anabolic activity of growth hormones.

"Our pilot double-blind study showed that a very-low-calorie ketogenic diet was highly effective in terms of body weight reduction without to induce lean body mass loss, preventing the risk of sarcopenia", the Italians wrote. "Further clinical trials are needed on a larger population and long-term body weight maintenance and risk factors management effects of a very-low-calorie ketogenic diet."

"As the full spectrum of metabolic effects induced by a very-low-calorie ketogenic diet is not completely characterized, new trials that are specifically designed to assess the combined effects of genotypes and dietary intervention are needed."

Eur Rev Med Pharmacol Sci. 2016 Jul;20(12):2613-21.

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