Objective: To examine the association of BMI with functional status and self-rated health among US adults and how the association differs by age and sex.
Methods and procedures: All analyses are based on the National Health Interview Survey (NHIS), 1997-2005, a yearly, representative study of the US household population. We pooled all survey years and fitted logistic regression for the two sexes and three age strata (ages 18-44, 45-64, and > or =65).
Results: Our study found that although underweight and severe obesity are consistently associated with increased disability and poorer health status, overweight and moderate obesity show associations that vary considerably by age and sex. For men, the adjusted odds ratios (ORs) for disability and poor/fair self-rated health tended to be lowest among overweight persons, especially for ages > or =45. Among men with moderate obesity, the risk of disability was elevated for ages 18-44 but lower for ages > or =65. For women, the adjusted ORs for disability and poor/fair self-rated health tended to be lowest among normal-weight persons, particularly for ages < or =45. Compared to normal-weight counterparts, overweight women aged > or =65 had a lower risk of disability but a somewhat elevated risk of poor/fair self-rated health.
Discussion: The results suggest that the association of BMI with functional status and self-rated health varies significantly across ages and sexes. The variations in the association of BMI with functional status and self-rated health suggest that a single "ideal body weight category" may not be appropriate for all persons or all health outcomes.