Weight loss and dropout during a commercial weight-loss program including a very-low-calorie diet, a low-calorie diet, or restricted normal food: observational cohort study123

BACKGROUND The effectiveness of commercial weight-loss programs consisting of very-low-calorie diets (VLCDs) and low-calorie diets (LCDs) is unclear. OBJECTIVE The aim of the study was to quantify weight loss and dropout during a commercial weight-loss program in Sweden (Itrim; cost: $1300/€1000; all participants paid their own fee). DESIGN This observational cohort study linked commercial weight-loss data with National Health Care Registers. Weight loss was induced with a 500-kcal liquid-formula VLCD [n = 3773; BMI (in kg/m(2)): 34 ± 5 (mean ± SD); 80% women; 45 ± 12 y of age (mean ± SD)], a 1200-1500-kcal formula and food-combination LCD (n = 4588; BMI: 30 ± 4; 86% women; 50 ± 11 y of age), and a 1500-1800-kcal/d restricted normal-food diet (n = 676; BMI: 29 ± 5; 81% women; 51 ± 12 y of age). Maintenance strategies included exercise and a calorie-restricted diet. Weight loss was analyzed by using an intention-to-treat analysis (baseline substitution). RESULTS After 1 y, mean (±SD) weight changes were -11.4 ± 9.1 kg with the VLCD (18% dropout), -6.8 ± 6.4 kg with the LCD (23% dropout), and -5.1 ± 5.9 kg with the restricted normal-food diet (26% dropout). In an adjusted analysis, the VLCD group lost 2.8 kg (95% CI: 2.5, 3.2) and 3.8 kg (95% CI: 3.2, 4.5) more than did the LCD and restricted normal-food groups, respectively. A high baseline BMI and rapid initial weight loss were both independently associated with greater 1-y weight loss (P < 0.001). Younger age and low initial weight loss predicted an increased dropout rate (P < 0.001). Treatment of depression (OR: 1.4; 95% CI: 1.1, 1.9) and psychosis (OR: 2.6; 95% CI: 1.1, 6.3) were associated with an increased dropout rate in the VLCD group. CONCLUSION A commercial weight-loss program, particularly one using a VLCD, was effective at reducing body weight in self-selected, self-paying adults.