Abstract MP011: Effect of a Low-Carbohydrate Versus a Low-Fat Weight Loss Program on Endothelial Function
Background: A concern about low-carbohydrate (CHO) diets is that a higher fat intake may adversely affect vascular health. We hypothesized that the effect of two weight loss programs on endothelial function would be similar. Each program included exercise but differed in that one included a low-CHO diet whereas the other a low-fat diet.
Methods: Overweight or obese but otherwise healthy persons (n=77), 30–65 years old, were randomly assigned to 6-months of an isocaloric low-CHO or low-fat diet, plus 3 times per week supervised aerobic and resistance exercise training. Endothelial function was assessed with non-invasive peripheral arterial tonometry using the Endopat device. Reactive hyperemia was induced after 5 minutes of upper arm occlusion of SBP. The reactive hyperemia peripheral arterial tonometry index (RH-PAT), the ratio between the digital pulse volume during reactive hyperemia and at rest was measured at baseline and after 6 months, as were body weight, BMI, waist circumference, total body fat and trunk fat percent, and BP.
Results: Sixty subjects (low-CHO group: n=31,74% women; low-fat group, n=29, 72% women) completed the study. At baseline, there were no group differences in the following variables and the combined values are: age, 50.0±8.7 years; weight, 215.4±32.7 lbs; BMI, 34.2±3.8 kg/m2; waist circumference, 103.1±8.7 cm; total body fat, 43.3±7.2%; trunk fat, 46.4±5.7%; SBP, 124.7±13.5 mm Hg; DBP, 74.2±9.5, RH-PAT, 2.32±0.44%. After 6 months, low-CHO versus low-fat subjects had a greater reduction in weight, −28.9±11.0 versus −18.7± 2.0 lbs, p<0.001; BMI, −4.7±2.0 versus −2.9±1.7, p<0.001; waist circumference, −12.1±6.0 versus −6.2±7.8 cm, p<0.01; body fat, −6.8±4.5 versus −4.0±3.9%, p>0.02. The groups did not differ in reduction of trunk fat percent, with an overall loss of − 5.5±5.7%, p<0.001, or BP, overall reduction −10.7±12.1/−8.6±8.2 mm Hg, p<0.001. After 6 months, there was no overall change in RH-PAT, p=0.64. By regression analysis, 6-month RH-PAT, adjusted for the baseline value, did not differ by group. However, an absolute 1% drop in trunk fat percent was associated with an absolute 0.29% (or relative 12.5%) increase in RH-PAT, p=0.05.
Conclusions: A key finding was the lack of an adverse effect on a marker of endothelial function in the low-CHO group. Successful weight loss and reductions in total and abdominal fat, and BP were achieved with both programs. Greater reductions in weight, BMI, waist circumference, and body fat occurred in the low-CHO group. Though overall endothelial function did not change in either group, when individual variations were examined, a greater percent loss in trunk fat was associated with enhanced endothelial function. These data suggest that loss of central fat is associated with improved vascular health, independent of the dietary content of the weight loss program.
- © 2012 by American Heart Association, Inc.