Current issues of ACP Journal Club are published in Annals of Internal Medicine


Etiology

Weight gain in women was associated with type 2 diabetes mellitus

ACP J Club. 1995 Sept-Oct;123:50. doi:10.7326/ACPJC-1995-123-2-050


Source Citation

Colditz GA, Willett WC, Rotnitzky A, Manson JE. Weight gain as a risk factor for clinical diabetes mellitus in women. Ann Intern Med. 1995 Apr 1;122:481-6.


Abstract

Objective

To examine the association between weight gain and the risk for type 2 diabetes mellitus in adult women.

Design

14-year cohort analysis study of women in the Nurses' Health Study who responded to a mailed questionnaire.

Setting

Community-based study.

Participants

114 824 registered nurses aged 30 to 55 years (100% women, 98% white) without diabetes, coronary heart disease, stroke, or cancer who responded to the initial questionnaire and were enrolled in the study in 1976. Participants responded to biennial questionnaires about development of type 2 diabetes, coronary heart disease, cancer, or other major illness, and they recorded their current weight, their weight at age 18, and the existence of diabetes in their immediate family. Women with diabetes, coronary heart disease, stroke, or cancer were not enrolled in the study.

Assessment of risk factors

Body mass index (BMI) (grouped into 10 categories ranging from < 22.0 kg/m2 to ≥ 35.0 kg/m2), weight change between age 18 years and 1976 (grouped into 8 categories), and family history of type 2 diabetes .

Main outcome measures

Relative risk (RR) and incidence rates of type 2 diabetes. Diagnosis of type 2 diabetes was confirmed by information obtained from a supplementary questionnaire, validated by review of a random sample of participants' medical records by an endocrinologist unaware of the questionnaire responses. Women who developed gestational diabetes or type 1 diabetes mellitus were excluded from analysis.

Main results

Type 2 diabetes was reported in 2204 women. The risk for type 2 diabetes increased as BMI increased. A BMI of 22.0 to 22.9 kg/m2 had an age-adjusted RR for type 2 diabetes of 2.9 (95% CI 2.0 to 4.1) compared with a BMI of < 22.0 kg/m2; a mean BMI of 24.0 to 24.9 kg/m2 had an RR of 5.0 (CI 3.6 to 6.6); and a BMI of 31.0 to 32.9 kg/m2 had an RR of 40.3 (CI 33.7 to 48.3). The association between BMI and type 2 diabetes remained consistent within different age groups and was also seen in women with a BMI ≥ 22.0 kg/m2 at 18 years of age. Weight gain was associated with risk for type 2 diabetes (RR for gain ≥ 20.0 kg 12.3, CI 10.9 to 13.8), whereas weight loss reduced risk for type 2 diabetes (RR for loss ≥ 20 kg 0.13, CI 0.1 to 0.3). Family history of diabetes was associated with risk for type 2 diabetes (age and BMI-adjusted RR in women with 1 parent with type 2 diabetes 1.92, CI 1.70 to 2.17; for women with 1 parent and 1 sibling 2.78, CI 2.18 to 3.55). Family history did not affect the association between weight gain and risk for type 2 diabetes.

Conclusions

Body mass index was associated with the risk for type 2 diabetes mellitus in adult women. The risk increased with weight gained since age 18 years. Weight loss was associated with a reduced risk for type 2 diabetes mellitus.

Source of funding: National Institutes of Health.

For article reprint: Dr. G.A. Colditz, Harvard Medical School, Channing Laboratory, 180 Longwood Avenue, Boston, MA 02115, USA. FAX 617-525-2008.


Commentary

At first glance, the results of this well-done study seem to break little new ground. All physicians know that adiposity is strongly associated with an increased risk for diabetes mellitus. The prospective design of the study and the huge sample size, however, provide strong supporting evidence for several more detailed conclusions. First, the RR for type 2 diabetes increases dramatically with increases in BMI. Second, the increased risk is significant even at normal or low-normal BMI levels. Third, weight gain during adulthood increases the risk for type 2 diabetes, and weight loss reduces this risk by an average of 50% in those who lose 5.0 kg.

These findings will help both patients and clinicians to realistically consider the RR for type 2 diabetes that is associated with a given BMI. Perhaps more importantly, they show that important clinical benefit can be achieved during adulthood by even modest weight loss. As valuable as these data are, however, they only marginally advance our ability to identify specific persons who will develop type 2 diabetes. In part, this relates to the low incidence of type 2 diabetes that was seen even in the more obese subgroups of the study.

We should also keep in mind that the study participants were predominantly white women. Although the results may well apply to men and to other ethnic groups, proof of this assumption awaits further study. It also remains to be seen whether a more accurate index of adiposity (e.g., body fat mass by bioelectric impedance) or the characterization of body fat distribution (e.g., computed tomographic measurement of visceral fat) will enhance our ability to accurately identify persons who are likely to develop type 2 diabetes (1, 2).

Paul D. Levinson, MD
Brown University School of MedicinePawtucket, Rhode Island, USA


References

1. Sowers JR. Modest weight gain and the development of diabetes: another perspective [Editorial]. Ann Intern Med. 1995;122:548-9.

2. Bray GA. Pathophysiology of obesity. Am J Clin Nutr. 1992;55(Suppl 2):488S-94S.