Recently there has been growing attention for the functional role of fat-free mass, the part of the body that consists mainly of muscle, fluid and bone. It has been suggested that fat-free mass can directly influence energy intake through feedback signals between the fat-free mass and the brain areas involved in controlling hunger and satiety. Indirectly, fat-free mass influences energy expenditure, both at rest and during exercise. Put simply: if you lose a lot of muscle mass during a slimming diet, you will later feel hungrier and burn less energy (calories).
The question is whether you can prevent or limit long-term weight gain by keeping the loss of fat-free mass during the weight-loss period to a minimum.
The answer comes from a study involving 141 women. The women, with an average age of 35, had a sedentary lifestyle and a BMI of 28. For a year they followed an 800 kcal diet until their BMI was below 25. The participants were randomly divided into three groups: one group followed the diet only, a second group followed the diet and did endurance training three times a week, and a third group combined the diet with strength training three times a week. On average, the women lost 12.1 kilos (11.6 kilos of fat and 0.5 to 1.6 kg of fat-free mass), but after a year they had regained 6 kilos on average. 95 percent of all participants had regained weight after a year.
There was a clear link between the amount of fat-free mass the women lost and their weight gain after a year: the greater the loss of fat-free mass, the greater the long-term weight gain. Women who lost fat-free mass during weight loss saw their weight increase by 20 percent more in the year after the diet than women who did not lose fat-free mass. As expected, the women who only dieted lost the most fat-free mass. Those who did strength training lost no fat-free mass.
These research results once again show that it is important to maintain and even increase muscle mass during a period of weight loss, and that a diet combined with strength training is strongly recommended if you want to avoid long-term weight gain.
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