Energy balance and hypothalamic effects of a high-protein/low-carbohydrate diet

Abstract

Diets high in fat or protein and extremely low in carbohydrate are frequently reported to result in weight loss in humans. We previously reported that rats maintained on a low carbohydrate-high fat diet (LC-HF) consumed similar kcals/day as chow (CH)-fed rats and did not differ in body weight after 7 weeks. LC-HF rats had a 45% decrease in POMC expression in the ARC, decreased plasma insulin, and increased plasma leptin and ghrelin. In the present study we assessed the effects of a low carbohydrate-high protein diet (HP: 30% fat, 65% protein, and 5% CHO) on body weight, caloric intake, plasma hormone levels and hypothalamic gene expression. Male rats (n=16) were maintained on CH or HP for 4 weeks. HP rats gained significantly less weight than CH rats (73.4 +/− 9.4 and 125.0 +/− 8.2 g) and consumed significantly less kcals/day (94.8 +/− 1.5 and 123.6 +/− 1.1). Insulin was significantly reduced in HP rats (HP: 1.8 +/− 0.6 vs. CH: 4.12 +/− 0.8 ng/ml), there were no differences between groups in plasma leptin and plasma ghrelin was significantly elevated in HP rats (HP: 127.5 +/− 45 vs. CH: 76.9 +/− 8 pg/ml). Maintenance on HP resulted in significantly increased ARC POMC (HP: 121 +/− 10.0 vs. 100 +/− 5.9) and DMH NPY (HP: 297 +/− 82.1 vs. CH: 100+/− 37.7) expression compared to CH controls. These data suggest that the macronutrient content of diets differentially influences hypothalamic gene expression in ways that can affect overall intake.

Influence of a high-protein diet on energy balance in obese cats allowed ad libitum access to food

“…In contrast, the maintenance requirement of protein for omnivores varies from approximately 5% of ME for the rat (NRC, 1995) to 8% of ME for the dog (NRC, 2006). It has been shown that both weight gain and energy intake are decreased in rats consuming a HP diet (Kinzig et al, 2007). In obese cats, the effect of ad libitum consumption of HP diets on energy balance is unknown.…”

Effects of Different Levels of Protein Intake and Physical Training on Growth and Nutritional Status of Young Rats

“…Studies performed with adults (both with animals and humans) have suggested that high protein diets, combined with physical training, result in lower body fat and higher fat-free mass (18,19). Studies have indicated that, among the benefits of this kind of diet, a reduction in liver lipogenesis may be observed (18,20).…”

“…Studies performed with adults (both with animals and humans) have suggested that high protein diets, combined with physical training, result in lower body fat and higher fat-free mass (18,19). Studies have indicated that, among the benefits of this kind of diet, a reduction in liver lipogenesis may be observed (18,20). We can speculate that the growing condition of the animals modifies amino acid metabolism, allowing a deviation of the carbon skeleton from the excessive amino acids to glucose and fatty acids synthesis, favoring lipogenesis (21).…”

Macronutrients and obesity: views, news and reviews

“…This finding is supported by the fact that ghrelin failed to induce body-weight gain in adrenoreceptor (β 1 , β 2 and β 3 ) -knockout mice [325]. It also worth noting that a study by Kinzig et al showed that elevated ghrelin levels were accompanied by increased pro-opiomelanocortin (POMC) expression [326]; and central POMC gene delivery results in decreased food intake and attenuated weight gain in obese Zucker rats [327].…”