Effects of different degrees of insulin resistance on endothelial function in obese adults undergoing alternate day fasting.

Obesity can have deleterious effects on insulin sensitivity leading to endothelial dysfunction. Whether alternate day fasting (ADF) can ameliorate insulin sensitivity in a way that improves endothelial function remains unknown. This study examined the impact of ADF on endothelium dependent flow mediated dilation (FMD) in obese subjects with different degrees of insulin resistance. Obese non-diabetic adults ( = 54) participated in an 8-week ADF protocol (25% energy intake "fast day", alternated with ad libitum intake "feast day"). Subjects were divided into tertiles according to degree of insulin resistance based on HOMA-IR (Homeostatic model assessment-Insulin resistance): tertile 1 (0.8-2.4), tertile 2 (2.5-3.6), tertile 3 (3.7-12.4). Body weight decreased ( < 0.001) by 4% in each tertile. Fat mass, lean mass, and visceral fat mass also decreased ( < 0.001) similarly in each tertile. After 8 weeks of ADF, FMD and adiponectin differed ( < 0.05) between tertile 1 (3±0%; 26±23%) versus tertile 3 (-3±0%; -13±10%). Changes in leptin did not differ between tertiles (tertile 1: -23±7%; tertile 2: -20±7%; tertile 3: -9±7%). Fasting glucose did not change in any tertile. Fasting insulin and HOMA-IR differed ( < 0.05) between tertile 1 (10±11%; 11±11%) versus tertile 3 (-27±8%; -30±9%). Plasma lipids, blood pressure and heart rate did not change in any tertile. Our data suggest that ADF may be effective for decreasing insulin resistance in insulin resistant subjects, but these changes have no effect on endothelial function.