High-protein diet selectively reduces fat mass and improves glucose tolerance in Western-type diet-induced obese rats

Abstract

-Obesity is an increasing health problem. Because drug treatments are limited, diets remain popular. High-protein diets (HPD) reduce body weight (BW), although the mechanisms are unclear. We investigated physiological mechanisms altered by switching diet induced obesity (DIO) rats from Western-type diet (WTD) to HPD. Male rats were fed standard (SD) or WTD (45% calories from fat). After developing DIO (50% of rats), they were switched to SD (15% calories from protein) or HPD (52% calories from protein) for up to 4 weeks. Food intake (FI), BW, body composition, glucose tolerance, insulin sensitivity, and intestinal hormone plasma levels were monitored. Rats fed WTD showed an increased FI and had a 25% greater BW gain after 9 wk compared with SD (P Ͻ 0.05). Diet-induced obese rats switched from WTD to HPD reduced daily FI by 30% on day 1, which lasted to day 9 (Ϫ9%) and decreased BW during the 2-wk period compared with SD/SD (P Ͻ 0.05). During these 2 wk, WTD/HPD rats lost 72% more fat mass than WTD/SD (P Ͻ 0.05), whereas lean mass was unaltered. WTD/HPD rats had lower blood glucose than WTD/SD at 30 min postglucose gavage (P Ͻ 0.05). The increase of pancreatic polypeptide and peptide YY during the 2-h dark-phase feeding was higher in WTD/HPD compared with WTD/SD (P Ͻ 0.05). These data indicate that HPD reduces BW in WTD rats, which may be related to decreased FI and the selective reduction of fat mass accompanied by improved glucose tolerance, suggesting relevant benefits of HPD in the treatment of obesity. diet-induced obesity; food intake; high-protein diet; gut hormones OBESITY HAS BECOME EPIDEMIC, and by the year 2030, half of the adult population is predicted to be obese in the United States (54). Its prevalence is expanding worldwide in industrialized countries and spreading also to less developed countries; therefore "globesity" is taking over many parts of the world (see World Health Organization homepage). The plethora of health consequences related to obesity involves increased risk of developing adult-onset Type 2 diabetes mellitus, dyslipidemia, arteriosclerosis, and certain forms of cancer, including colorectal and pancreatic cancer (25). Therefore, obesity represents a major medical problem in the United States, and 12% of the entire health care costs are spent taking care of obesity-related comorbidities (52). A modest 5 to 10% body weight loss in obese subjects has been shown to result in improvements of these metabolic disturbances (21, 53).Although two antiobesity drugs have recently been approved, drug treatment options are still very limited (26), and therefore, dietary interventions remain popular. In particular, the use of a high-protein diet is considered a beneficial strategy to achieve a long-term reduction in body weight (8,22,47,48). However, the means by which an isocaloric high-protein diet reduces body weight are not well understood. There is some evidence that protein decreases appetite by increasing anorexigenic signaling (16,34,55) and stimulates thermogenesis (13,57,58) in experi...

Dietary restriction in moderately obese rats improves body size and glucose handling without the renal and hepatic alterations observed with a high-protein diet

“…In our obese rats, both the HP diet and the dietary restriction in the PW group reduced the elevated glucose levels 60 min after a glucose load and improved the overall HOMA2-IR index compared with the NP diet provided ad libitum. This was consistent with previous reports of improved glucose handling in obese rats given HP diets (Stengel et al 2013). This reversal of the adverse effect of obesity on glucose handling (Kelley et al 2003) in both HP-OP and PW-OP rats may be attributed to lower body weight and less hepatic inflammation, as reflected by reduced circulating haptoglobin.…”

Egg White Hydrolysate Can Be a Low-Allergenic Food Material to Suppress Ectopic Fat Accumulation in Rats Fed an Equicaloric Diet

“…Each value is expressed as the mean6standard error [Exp A: n56 rats; Exp B: n53; Exp C (lipids-loading test): n513-15 mice; Exp C (smallintestinal transit test): n56-9 mice per group]. Statistical analysis of the differences among the three groups 1 Food efficiency and energy requirement were calculated by using a following formula: Food efficiency (g/g)5Body weight gain (g)/Food intake throughout the test period (g). 2 Sum of perirenal, epididymal, and mesenteric adipose tissue weight.…”

“…Dietary proteins have been shown to improve dietinduced obesity and IR (1). Egg white (EW) contains a high amount of protein with a high amino acid balance and is used as a physicochemical functional and nutritional food ingredient, but the allergenicity of EW proteins in humans is well known.…”

Dietary Whey and Casein Differentially Affect Energy Balance, Gut Hormones, Glucose Metabolism, and Taste Preference in Diet-Induced Obese Rats

“…In a meta-analysis of randomized clinical trials, dairy consumption together with energy restriction has been associated with a reduction in body weight, and fat mass particularly, in short-term studies (2). Dairy foods contain multiple components of which whey and casein proteins have been demonstrated to decrease weight gain and adipose reserves, and to improve diabetic control, in rodent models (3)(4)(5)(6)(7)(8). However, the underlying mechanisms by which whey and casein promote weight loss and improve diabetic control remain largely unknown.…”

“…Whey protein was found to be more satiating and also more effective than casein in decreasing food intake and/or weight gain in rodent models (3,(6)(7)(8)(9). However, it is unclear whether the reduction of food intake by the consumption of whey and casein in rodent models is due to satiety, aversion, or other nonspecific malaise.…”