Fitness Vs. Fatness

Posted on: 25 March 2008 by Gareth Hargreaves

A woman’s level of fitness predicts and prevents heart disease in women better than a focus on weight.

Which is less healthy; being overweight or being physically inactive?

A woman’s level of fitness predicts and prevents heart disease in women better than a focus on weight. However, being overweight is stronger indicator of risk for diabetes than level of physical activity in women.

Researchers have found that a higher body mass index (BMI) has a stronger association with development of diabetes than does physical inactivity, according to a study in the Journal of the American Medical Association (JAMA).

Dr Amy R. Weinstein and colleagues investigated the combined relationship of BMI and physical activity with diabetes to understand whether increasing physical activity levels reduces the elevated risk of diabetes from obesity. The study included 37,878 participants who were free of cardiovascular disease, cancer, and diabetes at the beginning of the study, and follow-up averaged about 7 years. Weight, height, and recreational activities were reported at the beginning of the study. Normal weight was defined as a BMI of less than 25; overweight, 25 to less than 30; and obese, 30 or higher. A 5'4" woman would have a BMI of 25 if she weighed 145 lbs; a BMI of 30 if she weighed 174 lbs. Active was defined as expending more than 1,000 calories on recreational activities per week.

The researchers found that individually, BMI and physical activity were significant predictors of incident diabetes. Compared with normal-weight individuals, overweight individuals had a 3.2 times increased risk for diabetes; obese individuals, a 9.1 times increased risk. For overall activity, compared with the least active, a decreased risk of diabetes ranged from 9 percent to 18 percent.

"We observed a modest reduction in the risk of diabetes with increasing physical activity level compared with a large increase in the risk with increasing BMI," said the researchers. They believe these findings underscore how important someone’s level of body fat is as a determinant of type 2 diabetes. “Because physical activity is a significant individual predictor and has a beneficial effect on BMI, it remains an important intervention for diabetes prevention. Our study suggests that to further reduce the risk of diabetes with physical activity, it should be performed in conjunction with achieving weight loss. By furthering our understanding of the relative influence of BMI and activity on diabetes, we may improve our ability to risk stratify patients and in turn may reduce the incidence of diabetes," they said.

While getting rid of excess weight may be important to prevent diabetes, fitness level may be more accurate than obesity in predicting cardiovascular disease risk in women. Women reporting higher levels of physical fitness have fewer coronary artery disease risk factors, less coronary artery disease, and a lower risk for cardiovascular events, whereas measures of obesity are not as strongly associated with these outcomes, according to a study in JAMA.

Individual contributions of obesity and physical fitness to risk of coronary heart disease (CHD) in women remain unclear. Most obesity studies have not adequately measured physical activity and many studies of physical fitness have excluded women with known or suspected coronary heart disease.

Dr Timothy R. Wessel, of the University of Florida College of Medicine, and colleagues investigated the relationships of physical fitness and obesity measures with CHD risk factors, coronary angiographic findings, and adverse cardiovascular events among a group of women undergoing coronary angiography to evaluate suspected ischemia (inadequate blood supply).

The study included measures of obesity - BMI, waist circumference, waist-hip ration, and waist-height ratio - and physical fitness. Participants included 936 women enrolled at the time of coronary angiography, and then assessed for adverse outcomes, with an average follow-up time of 3.9 years.

The researchers found that of 906 women, 76 percent were overweight, 70 percent had low functional exercise capacity, and 39 percent had obstructive coronary artery disease (CAD). "During follow-up, 337 (38 per cent) women had a first adverse event, 118 (13 per cent) had a major adverse event, and 68 (8 per cent) died. Overweight women were more likely than normal weight women to have CAD risk factors, but neither BMI nor abdominal obesity measures were significantly associated with obstructive CAD or adverse cardiovascular (CV) events after adjusting for other risk factors," the researchers said. Conversely, women with lower levels of physical fitness were significantly more likely to have CAD risk factors and obstructive CAD, at 44 per cent compared to 26 per cent, and each measure of energy expenditure increase was independently associated with an 8 per cent decrease in risk of major adverse CV events during follow-up.

"These results suggest that fitness may be more important than overweight or obesity for CV risk in women. Evaluation of physical activity and functional capacity using simple questionnaires should be an integral part of CV risk stratification, and interventions aimed at increasing physical fitness levels should be included in the management of all women at risk for CHD," the authors concluded.

Dr Steven N. Blair and Dr Tim S. Church of the Cooper Institute, Dallas, believe the findings provide a timely opportunity to examine an ongoing debate and offer a resolution.

"The results presented by Weinstein et al suggest that increased BMI is substantially more important for incident diabetes, and Wessel et al suggest that inactivity or low fitness is a greater threat to health in terms of CVD outcomes. In recent years, the 'fitness vs. fatness' issue has led to controversy and heated debate."

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