Design and testing of foods differing in protein to energy ratios.

School of Biological Sciences, The University of Sydney, Rm 322, Heydon Laurence Building, A08, Sydney, NSW, Australia.
Appetite (Impact Factor: 2.54). 10/2010; 55(2):367-70. DOI:10.1016/j.appet.2010.06.009
Source: PubMed

ABSTRACT Our aim was to design a selection of foods with differing proportions of protein but equal palatability in two settings, Sydney Australia and Kingston Jamaica. The foods were manipulated to contain 10, 15 or 25% E as protein with reciprocal changes in carbohydrate to 60, 55 or 45% E and dietary fat was kept constant at 30%. Naïve participants did not identify a difference in protein between the versions. On average, the versions were rated equal in pleasantness (Sydney-10%: 44±2, 15%: 49±2 and 25%: 49±2 Kingston-10%: 41±3, 15%: 41±3 and 25%: 37±3).

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    ABSTRACT: A significant contributor to the rising rates of human obesity is an increase in energy intake. The 'protein leverage hypothesis' proposes that a dominant appetite for protein in conjunction with a decline in the ratio of protein to fat and carbohydrate in the diet drives excess energy intake and could therefore promote the development of obesity. Our aim was to test the 'protein leverage hypothesis' in lean humans by disguising the macronutrient composition of foods offered to subjects under ad libitum feeding conditions. Energy intakes and hunger ratings were measured for 22 lean subjects studied over three 4-day periods of in-house dietary manipulation. Subjects were restricted to fixed menus in random order comprising 28 foods designed to be similar in palatability, availability, variety and sensory quality and providing 10%, 15% or 25% energy as protein. Nutrient and energy intake was calculated as the product of the amount of each food eaten and its composition. Lowering the percent protein of the diet from 15% to 10% resulted in higher (+12±4.5%, p = 0.02) total energy intake, predominantly from savoury-flavoured foods available between meals. This increased energy intake was not sufficient to maintain protein intake constant, indicating that protein leverage is incomplete. Urinary urea on the 10% and 15% protein diets did not differ statistically, nor did they differ from habitual values prior to the study. In contrast, increasing protein from 15% to 25% did not alter energy intake. On the fourth day of the trial, however, there was a greater increase in the hunger score between 1-2 h after the 10% protein breakfast versus the 25% protein breakfast (1.6±0.4 vs 25%: 0.5±0.3, p = 0.005). In our study population a change in the nutritional environment that dilutes dietary protein with carbohydrate and fat promotes overconsumption, enhancing the risk for potential weight gain.
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