Lose fat and maintain muscle with a high-protein diet that provides a large dose of amino acids at every meal.
Don’t make the mistake of skimping on protein while cutting calories because this will lead to significant muscle loss and a large drop in metabolic rate.
A study in Obesity Journal showed that the reason people on energy-restricted diets lose muscle along with fat is due to an increased rate of muscle protein breakdown rather than a slower rate of muscle protein building. Researchers had overweight adults go on a weight loss diet for a year that provided 1.0 g/kg of body weight of protein a day and an energy deficit of 500 calories.
Participants lost 7 percent of their body weight (about 3 kg of lean mass and 5 kg of fat) by three months. After a year, they lost 10 percent of their body weight (about 2 kg of fat mass and no more lean mass).
Protein synthesis rates did not slow at any point during the study. Plus, after eating a meal, protein synthesis was actually enhanced over baseline. This was surprising because studies of animals that are put on similar diets have shown that muscle is lost during energy restriction due to depressed rates of protein synthesis.
A lack of calories in the long-term means the anabolic response to feeding is blunted. However, in humans, it appears the anabolic response to eating is maintained. Muscle loss must come from increased rates of protein breakdown, probably in between meals.
A solution is to ensure you get regular doses of protein at every meal and snack in order to continually trigger protein synthesis and avoid muscle loss. A recent review of how various protein doses affect body composition found that eating at least 1.6 g/kg/body weight or protein a day may be necessary to avoid lean tissue loss during energy restriction.
In addition, if you want to limit the total amount of energy you eat, it is necessary to get the most amino acids out of the food you do eat. High-quality protein from animal sources is your best choice. Still, supplemental protein can help you achieve that large daily dose of protein, especially for snacks. Studies suggest whey protein is the superior source for building muscle.