The mean age of the participants was 48 ± 12 y (range: 18–81 y), BMI was 32 ± 5 (range: 18
–68), and waist circumference was 105 ± 13 cm (72–164); 83% of the participants were women, 4% were normal weight, 38% were overweight, 37% were class I obese, 15% were class II obese, and 6% were class III obese ().
Baseline characteristics (n = 9037) of participants in a 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)1
During the 5 y preceding baseline, 8% of all participants had hospital visits listing diagnoses for CVD and 2% with cancer. During the 6-mo period preceding baseline, 18% were dispensed antihypertensives, 12% antidepressants, 7% lipid-lowering drugs, 2% oral antidiabetics, 1% insulin, and 1% antipsychotics.
Weight loss after 1 y: intention-to-treat analysis
The unadjusted mean (±SD) weight change in the 3 weight-loss groups combined was −8.6 ± 8.0 kg (−9.5% of baseline body weight). Within-group weight changes were −11.4 ± 9.1 kg with the VLCD, −6.8 ± 6.4 kg with the LCD, and −5.1 ± 5.9 kg with the restricted normal-food diet (P < 0.001 for all within-group changes; and ). BMI, percentage weight loss, and waist circumference were likewise reduced in a dose-response relation according to caloric intake (). A higher proportion of participants in the VLCD group also lost ≥15% body weight, and there were fewer participants who lost <5% of body weight ().
TABLE 2 Changes in absolute and percentage body weight and waist circumference in participants after 1 y in a commercial weight-loss program (n = 9037) including a VLCD (500 kcal/d), an LCD (1200–1500 kcal/d), or a restricted normal-food diet (1500–1800 (more ...)
TABLE 3 Adjusted between-group differences in absolute and relative body weight and waist circumference in participants after 1 y in a commercial weight-loss program (n = 9037) including a VLCD (500 kcal/d), an LCD (1200–1500 kcal/d), or a restricted (more ...)
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 (more ...)
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 (more ...)
After adjustment for covariates (baseline body weight, age, sex, calendar year, center, comorbidities, and drug dispensations), the VLCD group lost 2.8 kg (95% CI: 2.5, 3.2) more than did the LCD group and 3.8 kg (95% CI: 3.2, 4.5) more than did the restricted normal-food diet. The LCD group lost 1.0 kg (95% CI: 0.4, 1.6) more than did the restricted normal-food diet group.
Weight loss after 1 y: completers-only analysis
In the completers-only analysis, the unadjusted mean (±SD) weight change for all 3 weight-loss groups was −10.9 ± 7.5 kg, equivalent to 12.0% of baseline body weight. Within-group, unadjusted weight changes were −13.9 ± 8.1 kg for the VLCD group, −8.8 ± 5.9 kg for the LCD group, and −6.9 ± 5.9 kg for the restricted normal-food group.
By using linear regression we found that higher baseline body weight (), greater initial weight loss, and female sex were associated with increased weight loss after 1 y across all weight-loss groups (P < 0.01–0.001; see Table S1 under “Supplemental data” in the online issue). A history of treatment with the previously available antiobesity drug sibutramine predicted a smaller weight loss after 1 y in the VLCD and LCD groups (P = 0.026 and P = 0.008, respectively).
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 (more ...)
Dropout after 1 y
Crude dropout rates were 18% in the VLCD group, 23% in the LCD group, and 26% in the restricted normal-food group. In multivariable analysis, with adjustment for age, sex, baseline BMI, center, calendar year, and comorbidities and drug dispensations, and with the use of the VLCD group as reference, dropout was significantly higher in the LCD group (OR: 1.43; 95% CI: 1.27, 1.62; P < 0.001) and restricted normal-food group (OR: 1.66; 95% CI: 1.37, 2.01; P < 0.001).
Within the VLCD group, younger age (<40 y) and low initial weight loss (<5%) after 3 mo were associated with an increased dropout rate (). Drug dispensations for depression and psychosis were also associated with an increased risk of dropout. Within the LCD group, predictors of dropout were younger age (<40 y), a low BMI at baseline (<30), and a low initial weight loss (<5% of baseline body weight). Sex, history of treatment of CVD or cancer, or drug dispensation for hypertension, dyslipidemia, or diabetes were not associated with dropout.
Multivariable-adjusted ORs (95% CIs) of dropouts at 12 mo during a commercial weight-loss program including a VLCD (500 kcal/d) or an LCD (1200–1500 kcal/d)1
To minimize the influence of choice of method for handling missing data, we carried out sensitivity analysis using last observation carried forward, a completers-only analysis, and multiple imputation. None of the 3 alternative data-imputation methods produced results that differed materially from the main analysis ().