Relationship of physical activity vs body mass index with type 2 diabetes in women.
BACKGROUND
Physical inactivity and body mass index (BMI) are established independent risk factors in the development of type 2 diabetes; however, their comparative importance and joint relationship with diabetes are unclear.


OBJECTIVE
To examine the relative contributions and joint association of physical activity and BMI with diabetes.


METHODS
Prospective cohort study of 37 878 women free of cardiovascular disease, cancer, and diabetes with 6.9 years of mean follow-up. Weight, height, and recreational activities were reported at study entry. Normal weight was defined as a BMI of less than 25; overweight, 25 to less than 30; and obese, 30 or higher. Active was defined as expending more than 1000 kcal on recreational activities per week.


METHODS
Incident type 2 diabetes, defined as a new self-reported diagnosis of diabetes.


RESULTS
During the follow-up, 1361 cases of incident diabetes occurred. Individually, BMI and physical activity were significant predictors of incident diabetes. Compared with normal-weight individuals, the multivariate-adjusted hazard ratio (HR) was 3.22 (95% confidence interval [CI], 2.69-3.87) for overweight individuals and 9.09 (95% CI, 7.62-10.8) for obese individuals. For overall activity (kilocalories expended per week), compared with the least active first quartile, the multivariate-adjusted HRs were 0.91 (95% CI, 0.79-1.06) for the second quartile, 0.86 (95% CI, 0.74-1.01) for the third, and 0.82 (95% CI, 0.70-0.97) for the fourth (P for trend =.01). In the combined analyses, overweight and obese participants, whether active or inactive, had significantly elevated risks, compared with normal-weight active individuals. The multivariate-adjusted HRs were 1.15 (95% CI, 0.83-1.59) for normal-weight inactive, 3.68 (95% CI, 2.63-5.15) for overweight active, 4.16 (95% CI, 3.05-5.66) for overweight inactive, 11.5 (95% CI, 8.34-15.9) for obese active, and 11.8 (95% CI, 8.75-16.0) for obese inactive participants.


CONCLUSIONS
Although BMI and physical inactivity are independent predictors of incident diabetes, the magnitude of the association with BMI was greater than with physical activity in combined analyses. These findings underscore the critical importance of adiposity as a determinant of diabetes.
Weinstein
Amy R
AR
Boston VA Healthcare System, MA, USA. aweinste@bidmc.harvard.edu
Sesso
Howard D
HD
Lee
I Min
IM
Cook
Nancy R
NR
Manson
JoAnn E
JE
Buring
Julie E
JE
Gaziano
J Michael
JM
D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009765:Obesity; D010809:Physical Fitness; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors