Background: Understanding the role of dietary quality in the progression of adiposity in populations already affected by overweight or obesity is crucial for the guidance of secondary prevention strategies. Objective: To examine the association of diet quality, as reflected by the French Nutrition and Health Programme (Programme National Nutrition Sante, PNNS) - Guideline Score (GS), with 6-year-changes in weight and waist circumference. Design and Methods: Subjects were 1029 male and 450 female participants of the SUplementation en VItamines et Mineraux AntioXydants (SU.VI.MAX) cohort (1994-2002) with anthropometric variables at baseline and follow-up and available data for estimating diet quality at baseline. We employed analysis of variance and covariance models to investigate anthropometric changes (% of the initial value) by categories of the PNNS-GS, which contains both dietary components and a physical activity component, and of a modified score (mPNNS-GS) containing dietary components only. Results: In men, a low (<6 points) PNNS-GS was associated with greater 6-year weight gain (adjusted mean: 3.63% [95% confidence interval: 2.87%; 4.39%]) as compared to a high (>= 9 points) PNNS-GS (2.10% [1.39%; 2.81%]); p = 0.01. Results for the mPNNS-GS were very similar. In women, no associations between diet scores and weight change were observed. No significant relation between dietary quality and change in waist circumference was present among either men or women. Conclusions: These results support a beneficial role of high dietary quality - as characterized by good adherence to official French nutritional guidelines - in secondary obesity prevention, among men.