A team from North Carolina, USA, assessed the development of body mass in young US adults.
They also examined the role of race or ethnicity, sex, and birth year in obesity onset.
In the prospective study, the National Longitudinal Survey of Youth (1979), a national sample with over-sampling of minority ethnic groups, was given to 9179 persons.
Body mass index (BMI) was calculated from 12 self-reported height and weight samples, and recorded between 1981 and 1998.
Logistic regression identified predictors of obesity at age 35 to 37 years.
In addition, Cox proportional hazards models compared the incidence of obesity by ethnicity and birth year.
Overall, 26% of men and 28% of women were found to be obese (BMI ≥ 30 kg/m2) by age 35 to 37 years.
|35 to 37-year-olds that are obese:|
| Annals of Internal Medicine |
Race or ethnicity and baseline BMI were significant predictors of obesity.
The authors discovered that obesity onset was 2.1-times faster for black women and 1.5-times faster for Hispanic women, than for white women.
The pattern for men differed.
Overall, obesity developed most rapidly in Hispanic men.
However, relative rates of obesity onset for white men, compared with black men, varied according to age.
The rate of obesity onset increased 26% to 28% over an 8-year span in birth year.
Dr Kathleen M. McTigue, of the University of North Carolina at Chapel Hill, said on behalf of her colleagues, "Marked ethnic-based differences were found in rates of weight accumulation in young US adults, with later birth cohorts experiencing earlier onset of obesity."
"To alter the course of obesity in the United States, interventions should target young adults, especially those of minority ethnic groups," she concluded.