Socioeconomic differences in weight gain and determinants and consequences of coronary risk factors.

BACKGROUND The increasing prevalence of overweight and obesity is a major public health concern in many developed countries. OBJECTIVE We aimed to describe socioeconomic differences in change in body mass index (BMI; in kg/m2) from age 25 y, assess possible factors behind these differences, and study whether socioeconomic differences in a variety of coronary risk factors can be accounted for by change in BMI. DESIGN The data come from a cohort study of London-based civil servants (Whitehall II), who participated in the first (1985-1988) and third (1991-1993) phases of the study and were 35-55-y old at phase 1: altogether there were 5507 men and 2466 women. Both study phases included a questionnaire and a screening examination. RESULTS In men and women, employment grade--the measure of socioeconomic status used in this cohort--was strongly related to BMI gain from age 25 y to phase 3 (25 y apart on average). The lower the grade the larger the gain in BMI. Adjustment for health behaviors reduced the grade differences in BMI gain by approximately 20%. A substantial part of the grade differences in diastolic and systolic blood pressure and plasma triacylglycerol concentrations could be accounted for by BMI change from age 25 y. CONCLUSIONS Grade differences in BMI change are evident, but many of the determinants of these differences remain unknown. If lower-status persons continue to gain weight more rapidly than higher-status persons, overweight is likely to be of growing importance as a pathway to social inequalities in ill health.