Clinical Briefs: Diet, Lifestyle, and Type 2 Diabetes in Women
Clinical Briefs: Diet, Lifestyle, and Type 2 Diabetes in Women
With Comments from John La Puma, MD, FACP
Source: Hu FB, et al. Diet, lifestyle, and the risk of type 2 diabetes mellitus in women. N Engl J Med 2001;345:790-797.
Previous studies have examined individual dietary and lifestyle factors in relation to Type 2 diabetes, but the combined effects of these factors are largely unknown.
Hu et al followed 84,941 female nurses from 1980 to 1996; these women were free of diagnosed cardiovascular disease, diabetes, and cancer at baseline. Information about their diet and lifestyle was updated periodically.
A low-risk group was defined according to a combination of five variables: A body-mass index (BMI = weight in kilograms divided by the square of the height in meters) of less than 25 kg/m2; a diet high in cereal fiber and polyunsaturated fat and low in trans fat and glycemic load (which reflects the effect of diet on the blood glucose level); engagement in moderate-to- vigorous physical activity for at least 30 minutes per day; no current smoking; and the consumption of an average of at least half a drink of an alcoholic beverage per day.
During 16 years of follow-up, 3,300 new cases of Type 2 diabetes were documented. Overweight or obesity was the single most important predictor of diabetes. Lack of exercise, a poor diet, current smoking, and abstinence from alcohol use all were associated with a significantly increased risk of diabetes, even after adjustment for the BMI.
As compared with the rest of the cohort, women in the low-risk group (3.4% of the women) had a relative risk of diabetes of 0.09 (95% confidence interval [CI], 0.05-0.17). A total of 91% of the diabetes cases in this cohort (95% CI, 83-95%) could be attributed to habits and forms of behavior that did not conform to the low-risk pattern.
These findings support the hypothesis that the majority of cases of Type 2 diabetes could be prevented by adopting a healthier lifestyle.
Comment
The Nurses’ Health Study began in 1976, when 121,700 female nurses 30-55 years of age responded to a questionnaire regarding medical, lifestyle, and other health-related information. Together with the Physicians’ Health Study, it is one of the major sources of what we know in epidemiological retrospect about nutrients and disease.
Here, the follow-up rate with respect to the incidence of diabetes in the overall cohort was 97%; the authors used cumulative update methods for dietary intake and physical activity, assessed every two years; BMI and smoking status were updated every two years; and information about alcohol intake was updated in 1984, 1986, and 1990.
The relative risk of diabetes was 38.8 for women with a BMI of 35 kg/m2 or higher and 20.1 for women with a BMI of 30.0-34.9 kg/m2, as compared with women who had a BMI of less than 23 kg/m2. The lowest quintile for exercise (0.5 hours per week) among those with a BMI higher than 30 kg/m2, promoted diabetes only half as much as 7.0 hours prevented it in women with BMIs lower than 25 kg/m2. But minimal exercise still was significantly and independently associated with diabetes development. Activities included brisk walking, heavy gardening, heavy housework, vigorous sports, jogging, and "other activities vigorous enough to build up a sweat."
Last year, Chandalia et al (N Engl J Med 2000;342:1392-1398) found that a high-fiber diet (total, 50 g; 25 g of soluble fiber and 25 g of insoluble fiber) containing unfortified, high-fiber foods, dropped mean daily preprandial plasma glucose concentrations by 13 mg/dL; total cholesterol concentrations by 6.7% (P = 0.02); triglyceride concentrations by 10.2% (P = 0.02); and very low- density lipoprotein cholesterol concentrations by 12.5% (P = 0.01).
And Field and colleagues (Arch Intern Med 2001;161:1581-1586) recently found that women with a BMI higher than 35 kg/m2 (now considered "severely obese," until they get to 40 kg/m2, when they are properly diagnosed as "morbidly obese") were 17 times more likely and men were 23 times more likely to develop diabetes than those of normal weight (BMI < 25 kg/m2). There was a linear dose-response curve.
The harder questions is "What can my patients do to lose weight, keep it off, and prevent diabetes?" The answer is almost as individual as are patients, but here are some guidelines:
- Diets that exclude whole food groups do not allow patients to maintain any weight lost. Don’t recommend them for weight loss.
- Eating simply, eating slower, and eating sitting down all help.
- Celebrate small successes. They add up to big ones in the minds of overweight and obese people, who are used to failing at this (though they may be highly successful at many other endeavors).
- Start with what people can do, and be very specific. Add just one new effort per week. "Eat only foods with a maximum of 3 g of saturated fat per serving today—look on the label," or "Walk four blocks by yourself five of the seven days this week. Do five blocks next week."
- Be positive, even if you don’t feel that way. Patients need it, especially from their doctor.
Recommendation
The authors properly note that excess body fat is the single most important determinant of Type 2 diabetes. Most people do not recognize the connection between overweight or obesity and diabetes. State this clearly to patients at risk, and tell them, specifically, what to do about it.
La Puma J. Diet, lifestyle and Type 2 diabetes in women. Altern Med Alert 2001;12:144.Subscribe Now for Access
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