Impact of high-protein diets with either moderate or low carbohydrate on weight loss, body composition, blood pressure and glucose tolerance in rats

One approach to achieve weight loss and decrease both obesity and associated morbidities involves high-protein, low-carbohydrate (HPLC) diets. This study compares the impact on metabolic health of HPLC and high-protein, medium-carbohydrate (HPMC) diets offered to diet-induced obese (DIO) rats. Wearding male rats were fed either a 37 % fat diet (n 48) or stock pellets (n 12) for 22 weeks. Rats fed the 37 % fat diet accumulated more body fat (26.6 versus 14.8 % body weight, P < 0.001) compared with those on stock diet. The DIO rats had higher systolic blood pressure (+ 6.6 mmHg, P= 0.002), fasting insulin (+ 63 % P= 0.006) and areas under the glucose (+ 21 %, P < 0.001) and insulin (+ 81 %, P< 0.001) curves following an oral glucose tolerance test. DIO rats were then separated into four groups and offered for 8 weeks either: ( 1) the 37 % fat diet; (2) an HPLC or (3) HPMC diet; or (4) fed the 37 % fat diet to the intake of the HPMC group. Rats offered the 37 % fat or HPLC diets gained while those on HPMC lost body fat. Blood pressure was not altered by the dietary switch. Both HPLC and HPMC rats had lowered fasting insulin (P=0.027) and improved homeostatic assessment (HOMA; P=0.011) that was not different from those of stock animals. These improvements occurred despite differences in fat gain, and indicate that both weight loss and macronutrient intake can impact favourably on obesity-associated morbidities.