Losing 10 Lbs With A Low-CHO Diet Plus Exercise Does Not Impair Vascular Function

Abstract

PURPOSE: A concern about low-CHO diets is that the higher amount of dietary fat may have adverse effects on vascular health. We compared the effect of two lifestyle programs on vascular function. Each included exercise but differed in that one group followed a low-CHO diet whereas the other followed a low-fat diet. METHODS: Overweight or obese but otherwise healthy subjects, aged 30-65 years, were randomly assigned to 6-monhts of an isocaloric low-CHO or a low-fat diet, in addition to a 3 times per week supervised exercise program following ACSM guidelines for aerobic and resistance training. This analysis compares vascular function at baseline versus responses at 10 lbs of weight loss so the difference between groups was the diet content rather than the amount of weight loss. Among 55 subjects in the study for at least 3 weeks, 23 of 28 in the low-CHO and 23 of 27 in the low-fat group reached 10 lbs of weight loss. Thus, results for 46 subjects (M=10, F=36) are reported. Vascular function was assessed by peripheral artery tonometry, which yields the reactive hyperemia index (RHI) for endothelial function and the augmentation index (AI) for arterial stiffness. Body weight, BP, and HR were also measured. RESULTS: There were no group differences at baseline and the combined group values are age, 49.6±9.3 years; body weight, 218.4± 36.6 lbs; BMI, 35.1±3.9 kg/m2; SBP, 116.3±12.7 mm Hg; DBP, 71.7±8.6; HR, 64.1±7.6 bpm; RHI, 2.30±0.48 %; and AI, 17.5±16.3 %. The low-CHO reached 10 lbs of weight loss sooner, at 45.4± 21.9 days versus 70.0±28.3 days in the low-fat group, p<0.01. The combined group reduced weight to 207.0±36.4 lbs and BMI to 33.2±3.9 kg/m2, each p<0.001 versus baseline. There were no changes in either group and the combined values are RHI, 2.30± 0.67%; AI, 18.4±19.3 %; SBP; 111.4±10.3 mm Hg; DBP, 68.2±9.3; and HR, 63.0±8.2 bpm. There were no group differences when adjusted for time to 10 lbs of weight loss. CONCLUSIONS: A low-CHO diet plus exercise achieved a 10 lb weight loss sooner than a low-fat diet plus exercise, with no detectable impairment of vascular function. Whereas these data suggest that lifestyle intervention that includes a low-CHO diet does not adversely affect vascular health, the long-term impact of these weight loss programs is yet to be determined.