OBJECTIVE To determine whether an intermittent very-low-calorie diet (VLCD) improves weight loss and glycemic control more than moderate caloric restriction alone.

RESEARCH DESIGN AND METHODS Individuals with type 2 diabetes (n = 54) who were ≥ 20% over ideal body weight participated in a 20-week behavioral weight control program. Subjects were randomized to either a standard behavioral therapy (SBT) group or to one of two VLCD groups. SBT subjects received a 1,500−1,800 kcal/day diet throughout. Both VLCD groups followed a VLCD for 5 consecutive days during week 2, followed by either intermittent VLCD therapy for 1 day/week for 15 weeks (1-day) or for 5 consecutive days every 5 weeks (5-day), with a 1,500−1,800 kcal/day diet at other times.

RESULTS Both VLCD groups lost more weight than the SBT group over the 20 weeks (P = 0.04). Although the groups did not differ in fasting plasma glucose (FPG) changes at 20 weeks, more subjects in the 5-day group attained a normal HbA_1c when compared with the SBT group (P = 0.04). This benefit was independent of the effects of weight loss. The best predictor of overall change in FPG and HbA_1c was the FPG response during the first 3 weeks of the program.

CONCLUSIONS Periodic VLCDs improved weight loss in diabetic subjects. A regimen with intermittent 5-day VLCD therapy seemed particularly promising, because more subjects in this group attained a normal HbA_1c. Moreover, the glucose response to a 3-week period of diet therapy predicted glycemic response at 20 weeks, and it was a better predictor of the 20-week response than initial or overall weight loss.