Objective: The purpose of the present longitudinal study was to describe the associations between the 5-year changes in body mass index (BMI) and alterations in the clusters of metabolic syndrome (MS)-related factors. Methods: The study population comprised 1099 middle-aged adults drawn from the Stanislas study. Individuals were stratified into four groups according to the 5-year changes in BMI (weight loss (o0 kg/m 2 ), and weight gain (0-1, 1-2 and 42 kg/m 2 )). Changes in various MS-related variables and clusters were compared between groups: anthropometric indices, blood pressure, lipid and inflammatory markers, liver enzymes, uric acid and the five summary factors extracted by using factor analysis ('risk lipids', 'liver enzymes', 'inflammation', 'protective lipids' and 'blood pressure').Results: There was a strong linear trend between increasing BMI and worsening of risk lipids and blood pressure factors for both men and women (Pp0.001). In men only, liver enzymes and protective lipids factors were significantly related to the 5-year gain of BMI (Pp0.001), whereas inflammation factor positively increased across the four BMI-change groups, in women only. Interaction terms for sex were statistically significant for inflammation and liver enzymes clusters. Conclusion: In our population, there was a strong linear trend between increasing BMI and worsening of various MS-related variables. More interestingly, the identification of five factors associated with BMI changes dependent to gender, support the hypothesis that weight gain, and probably obesity, trigger metabolic mechanisms that differ between men and women.