Increasing the Protein Content in a Carbohydrate-Free Diet Enhances Fat Loss during 35% but Not 75% Energy Restriction in Rats

Abstract

The purpose of the present study was to test the influence of the amount of protein in a carbohydrate-free diet during a weight reducing program using severe (75%) or more moderate (35%) energy restriction in rats. In Expt. 1, 3 groups (n = 6) consumed ad libitum a high-carbohydrate, low-fat diet [P21C69L10 containing 21% of energy as protein (P21), 69% carbohydrate (C69) and 10% lipids (L10)], a high-carbohydrate, high-fat diet (P21C34L45), or a carbohydrate-free, high-fat, high-protein diet (P55L45). In Expt. 2, 7 groups (n = 7) were studied. For 20 d, groups 1-4 consumed ad libitum diets containing macronutrients at the proportions indicated in their designations [P14C56L30 (control diet), P30L70, P50L50, and P90L10]. Groups 5-7 were pair-fed the same diets at the level of the spontaneous intake of the P90L10 group on the previous day (35% energy restriction). In Expt. 3, 5 groups (n = 7) were fed 1 of the following diets for 20 d. Group 1 consumed the control diet (P14C56L30) ad libitum. Groups 2-5 were energy restricted to 25% of the daily energy intake of group 1 with diets varying in their protein and lipid concentrations (P14C56L30, P50L50, P70L30, and P90L10). A high-fat content in the diet devoid of carbohydrate did not increase energy intake and body adiposity and neither body weight nor body composition was significantly affected by the protein to lipid ratio when energy restriction was 75%; however, a protein content > 50% preserved lean body mass at the expense of fat mass when energy restriction was 35%. Our results show that the absence of carbohydrates from the diet induces a low energy intake and the preferential deposition of protein.

High-glycemic index carbohydrates abrogate the antiobesity effect of fish oil in mice

“…Different letters indicate statistical difference, P Ͻ 0.05. development because mice receiving glybenclamide in combination with proteins and fish oil did not become obese. This finding is in keeping with the observation that a high-fat diet is unable to increase adipose tissue mass in the absence of carbohydrates (47,50). Together, these observations suggest that hyperinsulinemia is a contributing factor to the development of obesity, and reducing hyperinsulinemia would possibly counteract obesity development.…”

Energy restriction only slightly influences protein metabolism in obese rats, whatever the level of protein and its source in the diet

“…For instance, in the work of Marsset --Baglieri where rats were fed CHO-free diets, a 50% protein diet displayed a greater fat-mass loss than a 30% protein diet when animals were energy restricted to 35% but not to 75%. 36 In contrast, with a lower energy restriction (25%), it was reported that a high-fat diet (45% of total energy) attenuated the weight loss effect of energy restriction compared with a normalfat diet, and the reduction of visceral adipose depots was detectable early after the beginning of the restriction.…”

“…This result was consistent with that reported by McLean et al 37 who did not observe a significant fat-free mass loss in rats after a 40% energy restriction for 2 weeks. A loss of lean body mass was, however, observed in rats when more stringent energy restriction of at least 60% was applied, 36 but at lower levels it seemed that fat mass alone was sufficient to sustain energy needs.…”

A model for antipsychotic-induced obesity in the male rat

“…Unlike humans, rats have high protein intake (35%), high lipid intake (50%), and low carbohydrate intake (15%). We have recently shown that the interaction between carbohydrates and lipids is essential in the induction of obesity in rats fed with high-fat diets (Marsset-Baglieri et al 2004).…”