(12-07-10) Presence or absence of carbohydrates and the proportion of fat in a high-protein diet affect appetite suppression but not energy exp

Presence or absence of carbohydrates and the proportion of fat in a high-protein diet affect appetite suppression but not energy expenditure in normal-weight human subjects fed in energy balance.
Veldhorst MA, Westerterp KR, van Vught AJ, Westerterp-Plantenga MS.

Department of Human Biology, NUTRIM School for Nutrition, Toxicology and
Metabolism, Maastricht University Medical Centre, PO Box 616, 6200 MD
Maastricht, The Netherlands.
Abstract
Two types of relatively high-protein diets, with a normal or low proportion of
carbohydrates, have been shown effective for weight loss. The objective was to
assess the significance of the presence or absence of carbohydrates and the
proportion of fat in high-protein diets for affecting appetite suppression,
energy expenditure, and fat oxidation in normal-weight subjects in energy
balance. Subjects (aged 23 (sd 3) years and BMI 22.0 (sd 1.9) kg/m2) were
stratified in two groups. Each was offered two diets in a randomised cross-over
design: group 1 (n 22) - normal protein (NP; 10, 60 and 30 % energy (En%) from
protein, carbohydrate and fat), high protein (HP; 30, 40 and 30 En%); group 2
(n 23) - normal protein (NP-g; 10, 60 and 30 En%), high protein, carbohydrate-
free (HP-0C; 30, 0 and 70 En%) for 2 d; NP-g and HP-0C were preceded by
glycogen-lowering exercise (day 1). Appetite was measured throughout day 2
using visual analogue scales (VAS). Energy expenditure (EE) and substrate
oxidation (respiratory quotient; RQ) were measured in a respiration chamber
(08.00 hours on day 2 until 07.30 hours on day 3). Fasting plasma beta-
hydroxybutyrate (BHB) concentration was measured (day 3). NP-g and NP did not
differ in hunger, EE, RQ and BHB. HP-0C and HP v. NP-g and NP, respectively,
were lower in hunger (P < 0.05; P < 0.001) and RQ (P < 0.01; P < 0.001) and
higher in EE (P < 0.05; P = 0.07) and BHB (P < 0.05; P < 0.001). Hunger and RQ
were lower with HP-0C than HP (693 (sd 208) v. 905 (sd 209) mm VAS x 24 h, P <
0.01; 0.76 (sd 0.01) v. 0.81 (sd 0.02), P < 0.01); BHB was higher (1349 (sd
653) v. 332 (sd 102) mumol/l; P < 0.001). DeltaHunger, DeltaRQ, and DeltaBHB
were larger between HP-0C-NP-g than between HP-NP ( - 346 (sd 84) v. - 107 (sd
52) mm VAS x 24 h, P < 0.01; - 0.09 (sd 0.00) v. - 0.05 (sd 0.00), P < 0.001;
1115 (sd 627) v. 104 (sd 42) mumol/l, P < 0.001). In conclusion, appetite
suppression and fat oxidation were higher on a high-protein diet without than
with carbohydrates exchanged for fat. Energy expenditure was not affected by
the carbohydrate content of a high-protein diet.

Source: Br J Nutr. 2010 Jun 22:1-11. [Epub ahead of print]

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