Improvements in vascular health by a low-fat diet, but not a high-fat diet, are mediated by changes in adipocyte biology

Background: Low-fat (LF) and high-fat (HF) weight loss diets improve brachial artery flow-mediated dilation (FMD) in obese individuals, although results are conflicting. Moreover, the role that adipose tissue plays in mediating these diet-related effects are unknown. Objective: This study examined how modulations in FMD by HF and LF diets relate to changes in adipocyte parameters. Design: Obese subjects (n = 17) were randomized to a HF diet (60% kcal as fat) or a LF diet (25% kcal as fat) for 6 weeks. Both groups were restricted by 25% of energy needs. Results: Body weight decreased (P <0.05) in both groups (HF: -6.6 +/- 0.5 kg, LF: -4.7 +/- 0.6 kg). Fat mass and waist circumference were reduced (P <0.05) in the LF group only (-4.4 +/- 0.3 kg; -3.6 +/- 0.8 cm, respectively). FMD improved (P <0.05) in the LF group (7.4 +/- 0.8% to 9.8 +/- 0.8; 32% increase) and was impaired in the HF group (8.5 +/- 0.6% to 6.9 +/- 0.7; 19% reduction). Increases in plasma adiponectin (P <0.05, 16 +/- 5%), and decreases in resistin (P <0.05, -26 +/- 11%), were shown by the LF diet only. Greater decreases in leptin were observed with LF (-48 +/- 9%) versus HF (-28 +/- 12%) (P <0.05, diet x time). Increased FMD by the LF diet was associated with increased adiponectin, and decreased fat mass, waist circumference, leptin, and resistin. Conclusion: Beneficial modulations in vascular health by LF diets may be mediated by improvements in adipocyte parameters.