protein diets and weight loss

In the management of obesity the effect of diet composition on feeding behaviour is clearly important to encourage weight loss in the short term and weight maintenance in the longer term. Isoenergetic amounts of the dietary macronutrients are not equal in terms of their effect on appetite and motivation to eat.
The diet composition strongly affects ad libitum energy intake with protein being the most satiating macronutrient, independent of energy density, relative to carbohydrate and fat. The protein-induced satiety is important as hunger is one of the main reasons why subjects do not comply with a weight-loss regimen .Are such diets safe ?.
For example, recent studies have indicated greater weight loss can be achieved on high-protein diets when compared with high-carbohydrate, low-fat alternatives for periods up to 6 months, but by 12 months, all diets were equally effective. However high-protein low-carbohydrate diets are high in fat, and often the contributions of fruit, vegetables and whole grains is low, which runs counter to current healthy eating advice. There is also some recent evidence that high-protein low-carbohydrate diets may have implications for gut health. But many studies show improvements in fasting lipidaemia and/or glycaemic control on such diets. High-protein diets could be a powerful tool to promote weight loss in the short term.
It is not known how much protein is required to maximise protein-induced satiety or whether there is a relationship with the energy density of the diet. Normal protein intake is about 15 % of energy intake, which, for a sedentary adult male, is approximately 76-88 g/d. The high-protein diets reported for weight-loss studies often include about 30 % of energy intake as protein. This does not mean that protein intake (g) is doubled, as energy intake is reduced. Often the protein intake is increased only by 30-40 % over habitual levels.
It is not clear if protein promotes satiety (inter-meal interval) or satiation (meal termination) or, indeed, both. Humans eat and over consume energy for a variety of reasons, often not related to hunger.
. Johnstone 2009 High-protein diets for appetite control and weight loss-the “holy grail “ of dieting British J of Nutrition vol 101 pp 1729-1730

Martin Eastwood
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