The cornerstone to treat metabolic syndrome and insulin resistance is dietary intervention. Both low-carbohydrate diet (LCD) and low-fat diet (LFD) have been reported to induce weight loss and improve these conditions. One of the factors associated with a subject's adherence to the diet is satiety. The aim of this study was to evaluate the effects of LCD and LFD on body weight, appetite hormones, and insulin resistance. Twenty guinea pigs were randomly assigned to LCD or LFD (60%:10%:30% or 20%:55%:25% of energy from fat/carbohydrate/protein, respectively) for 12 weeks. Weight and food intake were recorded every week. After this period, animals were killed and plasma was obtained to measure plasma glucose and insulin, appetite hormones, and ketone bodies. Guinea pigs fed LCD gained more weight than those fed LFD. The daily amount of food intake in grams was not different between groups, suggesting that food density and gastric distension played a role in satiety. There was no difference in leptin levels, which excludes the hypothesis of leptin resistance in the LCD group. However, plasma glucagon-like peptide-1 was 47.1% lower in animals fed LCD (P<.05). Plasma glucose, plasma insulin, and insulin sensitivity were not different between groups. However, the heavier animals that were fed LFD had impairment in insulin sensitivity, which was not observed in those fed LCD. These findings suggest that satiety was dependent on the amount of food ingested. The weight gain in animals fed LCD may be related to their greater caloric intake, lower levels of glucagon-like peptide-1, and higher protein consumption. The adoption of LCD promotes a unique metabolic state that prevents insulin resistance, even in guinea pigs that gained more weight. The association between weight gain and insulin resistance seems to be dependent on high carbohydrate intake.

OBJECTIVE:To investigate the effects of long-term high-protein, low-carbohydrate diet on body weight and the expression of gastrointestinal hormones in diet-induced obesity rats.

METHODS:Twenty-four diet-induced obesity rat models were established by feeding fat-enriched diet, then were randomly divided into two groups by stratified sampling method by weight: the high-protein diet group (HP, 36.7% of energy from protein), and the normal chow group (NC, 22.4% of energy from protein), 12 rats in each group. The total calorie intake of each rat per day was similar and was maintained for 24 weeks, then body weight, visceral fat mass, fasting plasma ghrelin and glucagon-like peptide-1 (GLP-1) were determined, as well as protein expression of ghrelin in stomach, GLP-1 in ileum were detected by immunohistochemistry.

RESULTS:After 24 weeks, body weight of HP, NC groups were (490.92± 39.47) g and (545.55 ± 31.08) g, respectively (t = -3.664, P<0.01); visceral fat mass were (22.42± 7.04) g and (32.33 ± 9.27) g, respectively (t = -2.503, P<0.05); plasma ghrelin level were (2.36± 0.82) and (1.95 ± 0.64) ng/ml, respectively (t = 1.337, P>0.05), and plasma ghrelin level was negatively correlated to body weight (r = -0.370, t = -1.899, P<0.05), visceral fat mass (r = -0.454, t = -2.52, P<0.01); plasma GLP-1 concentration were (0.52± 0.13) and (0.71 ± 0.19) ng/ml, respectively(t = -2.758, P<0.05); ghrelin protein expression in stomach were 25 473± 8701 and 10 526 ± 6194, respectively (t = 2.501, P<0.05); GLP-1 protein expression in ileum were 27 431± 5813 and 36 601 ± 5083, respectively (t = -1.833, P = 0.081).

CONCLUSION:Long-term isocaloric high-protein, low-carbohydrate diet can reduce body weight and visceral fat, increase the expression of ghrelin, and decline GLP-1 expression in diet-induced obesity rats.