Low protein diets produce divergent effects on energy balance

Abstract

Diets deficient in protein often increase food consumption, body weight and fat mass; however, the underlying mechanisms remain poorly understood. We compared the effects of diets varying in protein concentrations on energy balance in obesity-prone rats. We demonstrate that protein-free (0% protein calories) diets decreased energy intake and increased energy expenditure, very low protein (5% protein) diets increased energy intake and expenditure, whereas moderately low protein (10% protein) diets increased energy intake without altering expenditure, relative to control diet (15% protein). These diet-induced alterations in energy expenditure are in part mediated through enhanced serotonergic and β-adrenergic signaling coupled with upregulation of key thermogenic markers in brown fat and skeletal muscle. The protein-free and very low protein diets decreased plasma concentrations of multiple essential amino acids, anorexigenic and metabolic hormones, but these diets increased the tissue expression and plasma concentrations of fibroblast growth factor-21. Protein-free and very low protein diets induced fatty liver, reduced energy digestibility, and decreased lean mass and body weight that persisted beyond the restriction period. In contrast, moderately low protein diets promoted gain in body weight and adiposity following the period of protein restriction. Together, our findings demonstrate that low protein diets produce divergent effects on energy balance.

Dietary Tryptophan Restriction Dose‐Dependently Modulates Energy Balance, Gut Hormones, and Microbiota in Obesity‐Prone Rats

“…The protein leverage theory postulates that protein intake is regulated in mammals such that protein‐deficient diets are overconsumed in an attempt to meet protein requirements, whereas protein‐rich diets decrease food intake to calibrate for protein needs . Consistent with this hypothesis, we and others have shown that protein‐deficient diets are hyperphagic and thermogenic, while protein‐rich diets are hypophagic in rodents . The responses to protein dilution are, in part, mimicked by dietary restriction of the amino acids methionine or leucine, which promote hyperphagia and thermogenesis , whereas dietary deprivation of essential amino acids causes anorexia and weight loss .…”

“…Restrictions of dietary protein , methionine by 80% , or leucine by 85% were reported to promote hyperphagia and thermogenesis; however, little is known of whether restriction of other essential amino acids also produces similar responses. Our study revealed several important findings on the effects of tryptophan restriction on energy balance.…”

“…The young OP‐CD rats were selected for the current study because they partly mimic the human condition , high‐fat feeding disrupts gut microbiota composition in obese rats , and the effects of protein or methionine restriction on energy balance were more predominant in younger rats than older rats. Following acclimation, during the restriction phase, the animals were randomized (103 ± 1.7 g; n = 8/group) to receive one of the following four isocaloric high‐fat diets (4.63 kcal/g; 40% fat, 45% carbohydrates, 15% amino acid nitrogen; Table ) with varying concentrations of tryptophan for 21 days: control (CON) (0.205% w/w tryptophan as fed or 100% of tryptophan requirements), 0.143% w/w tryptophan as fed (70% of tryptophan requirements, 70TRP), 0.082% w/w tryptophan as fed (40% of tryptophan requirements, 40TRP), or 0.020% w/w tryptophan as fed (10% of tryptophan requirements, 10TRP). Diets were made in‐house based on American Institute of Nutrition (AIN)‐93 recommendations , with protein provided in the form of free amino acid mixtures.…”

“…To test whether β‐adrenergic receptors mediate the effects of tryptophan restriction on energy expenditure, propranolol (Catalog # P8688; Sigma‐Aldrich, Oakville, Ontario, Canada), a β1‐ and β2‐adrenergic receptor blocker, was administered on day 15 and day 17. In a crossover design, each rat received a subcutaneous injection of vehicle (0.9% NaCl) or propranolol (10 mg/kg) at ∼10 minutes before dark onset (1030 hours) followed by data acquisition for the next ∼22 hours, with ∼48 hours between injections, as we reported before .…”

Dietary Factors in Fasting Blood Glucose Levels and Weight Gain in Female Sprague Dawley Rats

“…This goes to support the fact that even lean people with less fat mass grower's mash specially prepared for the growth of poulets that are of commercial use. Diets deficient in protein often increase food consumption, body weight and fat mass [26][27][28][29][30]; however, the underlying mechanisms remain poorly understood of the underlying mechanisms by which moderate protein deficiency…”