Background: The effects of weight-loss attempts on long-term weight gain remain unclear.
Objective: The objective was to study prospectively how attempts to lose weight relate to future risk of major weight gain (>10 kg) and whether familial factors affect this relation.
Design: Participants in the Finnish Twin Cohort (3536 men and 4193 women aged 18-54 y at baseline) were followed up for 6-15 y. The role of familial factors was studied in 1705 twin pairs in this cohort who were discordant for weight-loss attempts at baseline. Baseline (1975) and follow-up (1981 and 1990) data-including weight, weight-loss attempts (dieting), and selected confounders-were obtained via mailed questionnaires.
Results: Average weight gain was at most weakly associated with weight-loss attempts. The risk of major weight gain for subjects attempting to lose weight at baseline was greatest among initially young (18-29 y) men (over 6 and 15 y, respectively-odds ratios: 2.01 and 1.74; 95% CI: 1.13, 3.57 and 1.11, 2.75) and middle-aged (30-54 y) women (over 6 and 15 y, respectively-2.43 and 1.52; 1.33, 4.42 and 1.06, 2.22) and persisted after potential confounders were controlled for. These risks decreased and became nonsignificant in the pairwise twin analysis, suggesting that the relation between dieting and subsequent major weight gain may also have a familial component.
Conclusions: Weight-loss attempts may be associated with subsequent major weight gain, even when several potential confounders are controlled for. Genetic and familial factors may contribute to this association.