Biochemical, Anthropometric, and Physiological Responses to Carbohydrate-Restricted Diets Versus a Low-Fat Diet in Obese Adults: A Randomized Crossover Trial.

Some research supports high-fat carbohydrate (CHO)-restricted diets for weight and fat loss and improvement of cardiovascular disease risk factors. To test this, a randomized crossover study was designed. Subjects (17 obese men and women [BMI: 30-38 kg/m2]) were fed three diets (supplying 1600 and 2200 kilocalories (kcal)/day for women and men, respectively) for 4 weeks, with each trial separated by 4-week washout periods. One CHO-restricted diet (10% CHO, 50% fat, and 40% protein content) was rich in plant foods and mushrooms, while the other CHO-restricted diet included more animal foods (10% CHO, 60% fat, and 30% protein content). The third diet was lower in fat and protein content (LF) and higher in CHOs (61% CHO, 21% fat, and 18% protein content). Body composition was assessed through hydrostatic weighing before and after each diet trial. Fasting blood samples were collected weekly for analysis of hormones and lipids. Data were analyzed through repeated measures analysis of variance with post hoc paired comparison t-tests. Weight and fat loss were similar (P > .05) among trials. Subjects lost lean mass (P < .05) during CHO-restricted trials, but not in the LF trial. Insulin concentrations decreased (P < .05) during the CHO-restricted trial and tended (P = .05) to decrease during the LF trial. Total cholesterol decreased (P < .05) for all trials; however, high-density lipoprotein cholesterol decreased (P < .05) and triacylglycerols were higher (P < .05) following the LF trial. Taken together, energy restriction regardless of diet composition promoted similar weight loss; however, CHO-restricted diets based on either plants/mushrooms or animal foods elicited a more beneficial lipid-altering effect in comparison with the LF diet.

Effects of conjugated linoleic acid supplementation on blood lipids and adiposity of rats fed diets rich in saturated versus unsaturated fat.

Conjugated linoleic acid (CLA) may decrease adiposity and improve blood lipid profiles under some conditions. The goal of this study was to determine the effects of CLA supplementation on blood lipid profiles and adiposity of rats fed a diet containing a primarily saturated fat versus a diet containing a primarily unsaturated fat. Twenty-eight male Sprague-Dawley rats were randomly assigned to one of four diets containing coconut oil, coconut oil with CLA, corn oil or corn oil with CLA. After 28 days, blood was collected and serum concentrations of total cholesterol (TC), HDL-cholesterol (HDL-C), and triacylglycerols (TG) were assessed. Food intake, body weights, and epididymal fat pads were measured. No significant differences (p>0.05) were noted among groups for amount of food consumed, weight gained, food efficiency ratio or serum TG concentrations. TC concentrations were lower (p<0.05) in the CLA-supplemented rats that were fed coconut oil but not those consuming corn oil. Serum HDL-C was lower (p<0.05) in rats consuming corn oil but was not significantly different (p>0.05) for CLA supplemented groups. Epididymal fat pads weighed significantly more (p<0.05) in the coconut oil fed group compared to the corn oil fed group, but there was no significant difference (p>0.05) between the corn oil and coconut oil + CLA group. Overall, this study suggests that CLA is more beneficial for control of blood lipids and adiposity when supplemented to a diet rich in saturated versus unsaturated fat.