Adiposity Compared With Physical Inactivity and Risk of Type 2 Diabetes in Women

  1. Jamal S. Rana, MD, PHD1,
  2. Tricia Y. Li, MD23,
  3. JoAnn E. Manson, MD, DRPH345 and
  4. Frank B. Hu, MD, PHD234
  1. 1Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
  2. 2Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts
  3. 3Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts
  4. 4Channing Laboratory, Harvard Medical School and Brigham and Women’s Hospital, Boston, Massachusetts
  5. 5Division of Preventive Medicine, Harvard Medical School and Brigham and Women’s Hospital, Boston, Massachusetts
  1. Address correspondence and reprint requests to Frank Hu, Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115. E-mail: frank.hu{at}channing.harvard.edu

Abstract

OBJECTIVE—The relative contribution of adiposity and physical inactivity to the risk of developing type 2 diabetes remains controversial.

RESEARCH DESIGN AND METHODS—We prospectively examined the individual and joint association of obesity and physical activity with the development of type 2 diabetes in 68,907 female nurses who had no history of diabetes, cardiovascular disease, or cancer at baseline. Adiposity was measured by BMI and waist circumference. Physical activity was assessed through average hours of moderate or vigorous exercise and computation of an MET score.

RESULTS—We documented 4,030 incident cases of type 2 diabetes during 16 years of follow-up (from 1986 to 2002). In a multivariate model including age, smoking, and other diabetes risk factors, risk of type 2 diabetes increased progressively with increasing BMI (P < 0.001) and waist circumference (P < 0.001) and with decreasing physical activity levels (P < 0.001). In joint analyses of BMI and physical activity, using women who had a healthy weight (BMI <25 kg/m2) and were physically active (exercise ≥21.8 MET h/week) as the reference group, the relative risks of type 2 diabetes were 16.75 (95% CI 13.99–20.04) for women who were obese (BMI ≥30 kg/m2) and inactive (exercise <2.1 MET h/week), 10.74 (8.74–13.18) for women who were active but obese, and 2.08 (1.66–2.61) for women who were lean but inactive. In combined analyses of waist circumference and physical activity, both variables were significant predictors of type 2 diabetes, but the association for waist circumference was substantially stronger than that for physical inactivity.

CONCLUSIONS—Obesity and physical inactivity independently contribute to the development of type 2 diabetes; however, the magnitude of risk contributed by obesity is much greater than that imparted by lack of physical activity.

Footnotes

  • A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

    The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Accepted October 6, 2006.
    • Received July 11, 2006.
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