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 study

Abstract

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.

FIGURE 1.

Absolute values for and changes in BMI, body weight, and waist circumference during a 12-mo commercial weight-loss program including a VLCD (500 kcal/d), an LCD (1200–1500 kcal/d), or a restricted normal-food diet (1500–1800 kcal/d). ANCOVA was conducted, and the data are estimated marginal means adjusted for age, sex, center, calendar year, history of cardiovascular disease and cancer, and dispensation of drugs for obesity, diabetes, hypertension, dyslipidemia, depression, or psychosis. Error bars represent 95% CIs. ITT: BOCF, intention to treat with use of baseline observation carried forward; ITT: LOCF, intention to treat with use of last observation carried forward; ITT: MI, intention to treat with use of multiple imputation; LCD, low-calorie diet; VLCD, very-low-calorie diet.

FIGURE 2.

Categories of percentage weight loss at 1 y in a commercial weight-loss program including a VLCD, an LCD, or a restricted normal-food diet. The analyses were conducted as both intention to treat with baseline substitution and completers only. Error bars represent 95% CIs. LCD, low-calorie diet; VLCD, very-low-calorie diet.

FIGURE 3.

Independent effects of baseline BMI (in kg/m²) and a VLCD (500 kcal/d; n = 3773), an LCD (1200–1500 kcal/d; n = 4588), and a restricted normal-food diet (1500–1800 kcal/d; n = 676) at predicting percentage weight loss after 1 y in a commercial weight-loss program. ANCOVA was conducted with adjustment for age, sex, center, calendar year, history of cardiovascular disease and cancer, and dispensation of drugs for obesity, diabetes, hypertension, dyslipidemia, depression, and psychosis. Data are estimated marginal means. LCD, low-calorie diet; VLCD, very-low-calorie diet.