Benefit of a low-fat over high-fat diet on vascular health during alternate day fasting.

BACKGROUND: Alternate day fasting (ADF) with a low-fat (LF) diet improves brachial artery flow-mediated dilation (FMD). Whether these beneficial effects can be reproduced with a high-fat (HF) diet remains unclear. OBJECTIVE: This study compared the effects of ADF-HF to ADF-LF regimens on FMD. The role that adipokines have in mediating this effect was also investigated. METHODS: Thirty-two obese subjects were randomized to an ADF-HF (45% fat) or ADF-LF diet (25% fat), consisting of two phases: (1) a 2-week baseline weight maintenance period and (2) an 8-week ADF weight loss period. Food was provided throughout the study. RESULTS: Body weight was reduced (P<0.0001) in the ADF-HF (4.4±1.0 kg) and ADF-LF group (3.7±0.7 kg). FMD decreased (P<0.05) by ADF-HF relative to baseline (7±1 to 5±2%) and increased (P<0.05) by ADF-LF (5±1 to 7±2%). Blood pressure remained unchanged in both groups. Adiponectin increased (P<0.05) in the ADF-HF (43±7%) and ADF-LF group (51±7%). Leptin and resistin decreased (P<0.05) in the ADF-HF (32±5%; 23±5%) and ADF-LF group (30±3%; 27±4%). Increases in adiponectin were associated with augmented FMD in the ADF-LF group only (r=0.34, P=0.03). CONCLUSION: Thus, improvements in FMD with ADF may only occur with LF diets and not with HF diets, and adipokines may not have a significant role in mediating this effect.

Alternate day fasting increases LDL particle size independently of dietary fat content in obese humans.

Alternate day fasting (ADF) with a low-fat (LF) diet increases low-density lipoprotein (LDL) particle size. Whether these beneficial effects can be reproduced by a high-fat (HF) ADF diet is unclear. This study compared an ADF-HF to an ADF-LF diet on plasma lipids, LDL size and high-density lipoprotein (HDL) size. Thirty-five obese subjects were randomized to an ADF-HF or ADF-LF diet for 10 weeks. Body weight decreased (P<0.0001) by 4.3±1.0 kg (4.8±1.1%) and 3.7±0.7 kg (4.2±0.8%) in the ADF-HF and ADF-LF group, respectively. LDL cholesterol was reduced (P<0.0001) by 19±8 mg/dl (18±5%) by ADF-HF and 28±7 mg/dl (25±3%) by ADF-LF. LDL particle size increased (P<0.005) by 3±1 Å in both groups. The proportion of small LDL particles decreased (P<0.005) by 8±2% and 11±3% in the ADF-HF and ADF-LF groups, respectively. HDL cholesterol and HDL size remained unchanged. Thus, our results suggest that the ADF-HF diet is equally as effective as the ADF-LF diet in improving LDL particle size and distribution.