Which Protein Fills You Up Most?

Dietary proteins have been shown to be more effective at prolonging satiety and suppressing food intake than carbohydrates and fats. However, different dietary proteins appear to vary in their ability to influence satiety and reduce food intake.

This is nicely demonstrated in a new study by Sebely Pal and Vanessa Ellis from the University of Curtin, Perth, Australia, published in the British Journal of Nutrition.

Pal and Ellis studied 22 healthy male normal-weight volunteers, who were studied on four separate occasions in a randomised, single blind, cross-over design study. On each occasion the subjects were given a liquid test meal, containing either tuna, turkey, whey or egg albumin, administered as a chocolate-flavoured shake.

Whey protein resulted in a significantly lower blood glucose and significantly higher insulin response than the same amount of tuna, egg, or turkey protein. Similarly, subjects rated their level of hunger as lower after the whey protein compared to the other proteins.

Most importantly perhaps, mean energy intake at an ad libitum meal four hours after the test meal was around 100 KCal lower with the whey meal than with the tuna, egg and turkey meals.

The authors speculate that this satiating effect of whey proteins may be related to the fact that whey protein has a faster rate of digestion and absorption than other proteins, producing a rapid peak in plasma amino acids which may contribute to their effect on satiety. Whey proteins also have one of the highest concentrations of branched-chain amino acids (BCAA) compared to other protein sources, which, in turn, may affect release of enteral hormones or insulin.

Interestingly, insulin, apart from its well-known actions on glucose and lipid metabolism, is also thought to be a satiety hormone, with increased insulin levels in the brain eliciting a net catabolic response influencing food intake regulatory mechanisms

Although these findings suggest a potential for hunger suppression and weight loss in overweight or obese individuals, it would be important to show that there is no compensatory effect in caloric intake that may develop over time as subjects go into negative energy balance over time.

Such an effect would ultimately defend body weight and prevent long-term weight loss.

Nevertheless, the study supports the notion that at least in the acute setting, all proteins may not be equal in their ability to satiate and decrease hunger.

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Pal S, & Ellis V (2010). The acute effects of four protein meals on insulin, glucose, appetite and energy intake in lean men. The British journal of nutrition, 1-8 PMID: 20456814