Trends in the Association of Parental History of Obesity over 60 Years

OBJECTIVE: The association of familial as compared to genetic factors in the current obesogenic environment, compared to earlier, leaner time periods, is uncertain. DESIGN AND METHODS: Participants from the Framingham Heart Study were classified according to parental obesity status in the Original, Offspring, and Third Generation cohorts; mean BMI levels were estimated and we compared the association of parental history across generations. Finally, a genetic risk score comprised of 32 well-replicated single nucleotide polymorphisms for BMI was examined in association with BMI levels in 1948, 1971, and 2002. RESULTS: BMI was 1.49 kg/m(2) higher per each affected parent among the Offspring, and increased to 2.09 kg/m(2) higher among the Third Generation participants (p-value for the cohort comparison=0.007). Parental history of obesity was associated with increased weight gain (p<0.0001) and incident obesity (p=0.009). Despite a stronger association of parental obesity with offspring BMI in more contemporary time periods, we observed no change in the effect size of a BMI genetic risk score from 1948 to 2002 (p=0.11 for test of trend across the time periods). CONCLUSIONS: The association of parental obesity has become stronger in more contemporary time period, whereas the association of a BMI genetic risk score has not changed.