Evidence suggests that high protein diets are beneficial in weight loss. A number of studies have investigated the effects of high protein diets and found that they may decrease short term appetite, increase general satiety, and increase resting metabolic rate. The effects of high protein diets may derive in part from their ability to change the physiology of the gastrointestinal system through the release of various hormones and other signal molecules, and these changes may in turn cause more systemic effects, particularly in the brain. Many gut derived hormones for example, despite being shown to act locally on the gastrointestinal tract, also play a role in negative feedback circuits to parts of the brain, particularly the hypothalamus, suggesting they play an important role in homeostasis. It is suspected that some of these hormonal signals may become dysfunctional as obesity develops and therefore there is an interest in understanding the effects of protein on the gastrointestinal tract of lean versus obese individuals.
For example, in one study, researchers investigated the effects of whey protein on the release of gut hormones and changes to gastrointestinal physiology in a group of obese individuals. A group of lean individuals acted as controls to allow a comparison between the two groups. In the obese subjects the ingestion of hydrolysed whey protein to the duodenum at a rate of 3 kcal per min resulted in suppression of antral (stomach) and duodenal (intestinal) pressures, an increase in the release of cholecystokinin (a hormone that decreases stomach emptying rate and increases satiety), glucagon-like peptide 1 (GLP 1), gastrointestinal peptide (GIP), insulin and glucagon (both GLP 1 and GIP are incretins that stimulate the release of insulin). In addition, there was a reduction in energy intake, in a dose dependent manner, supporting evidence that protein is an appetite suppressant. Differences between obese and lean subjects existed only in the insulin (greater in the obese) and GIP (lower in the obese) responses to the protein.
High protein diets may have similar physiological effects in both lean and obese subjects. In particular, the hormonal changes they induce may favour weight loss.
Therefore, the response to protein seen in obese subjects is not characterised by severe dysfunction. High protein diets may therefore have beneficial physiological effects in the obese including the suppression of appetite and a beneficial effect on postprandial glycaemia through the inhibition of stomach content emptying. These effects are also apparent in lean subjects and so high protein diets may prevent weight gain in the lean. These effects are certainly seen anecdotally in those that choose to consume higher protein diets. Another interesting finding of this study was the ability of the protein to stimulate insulin release through the release of the incretin hormones GLP 1 and GIP. Differences did exist between the obese and lean subjects in this regard but it is unclear what effect this may have. It is certainly expected that the obese may have an exaggerated response of insulin to the presence of protein in the gut, as it would be likely that a certain amount of insulin resistance would be present in these individuals.
Eat Well, Stay Healthy, Protect Yourself
RdB
