This study compared the effects of alternate day fasting (ADF) to daily calorie restriction (CR) on body weight and glucoregulatory factors in adults with obesity and insulin resistance.


This secondary analysis examined the data of insulin resistant subjects (n = 50) who participated in a 12-month study comparing ADF (25% energy needs on “fast days”; 125% needs on alternating “feast days”) to CR (75% energy needs every day) and a no-intervention control group.


In insulin resistant subjects, ADF and CR produced comparable body weight reductions (ADF: -6 ± 1%; CR: -5 ± 1%) by month 12 (P < 0.0001), relative to controls. Fat mass decreased similarly by ADF (-10 ± 3%) and CR (-9 ± 2%) versus controls. ADF produced greater decreases (P < 0.05) in fasting insulin (-50 ± 6%) and insulin resistance (-46 ± 6%) when compared to CR (-13 ± 8%; -14 ± 9%) and controls by month 12. Lean mass, visceral fat mass, LDL cholesterol, HDL cholesterol, triglycerides, blood pressure, CRP, TNF-a, and IL-6 remained unchanged.


These findings suggest that ADF may produce greater reductions in fasting insulin and insulin resistance versus CR, in insulin resistant subjects, despite similar decreases in body weight.