Friday, April 27, 2012

Fat positivity, BMI and some surveys

I am torn on the issue of fat positivity. I get what feminist do and how they try to help people, but sometimes I get the feeling health issues are overlooked. Here is some stuff I found via reddit:

Body-mass index BMI, the 200-year-old formula widely used by medical experts, health insurers and the fitness industry, may be categorising almost half of women and just over 20 per cent of men as healthy when their body-fat composition suggests they are obese, a US new study has found. [...]

To measure fatness, they used a costly diagnostic test called dual-energy X-ray absorptiometry, or DXA, and calculated subjects' level of obesity based on fat-composition standards used by the American Society of Bariatric Physicians.

The results also suggest that the BMI is a poor measure of fatness in men - but not always in a way that underestimates their obesity. In all, 20 per cent of the study's men shifted from normal and healthy into the obese column under the new measure.

But far more frequently than was the case among women, men who were obese by the BMI standard were reclassified as normal and healthy when they were measured with the DXA.


Abstract Obesity, android fat distribution, and other anthropometric measures have been associated with coronary heart disease in long-term prospective studies. However, fluctuations in weight due to age-related hormonal changes and changes in lifestyle practices may bias relative risk estimates over a long follow-up period. The authors prospectively studied the association between body mass index (BMI) (kg/m2), waist-to-hip ratio, and height as independent predictors of incident coronary heart disease in a 3-year prospective study among 29,122 US men aged 40-75 years in 1986. The authors documented 420 incident coronary events during the follow-up period. Body mass index, waist-to-hip ratio, short stature, and weight gain since age 21 were associated with an increased risk of coronary heart disease. Among men younger than 65, after adjusting for other coronary risk factors, the relative risk was 1.72 (95% confidence interval (CI) 1.10-2.69) for men with BMI of 25-28.9, 2.61 (95% CI 1.54-4.42) for BMI of 29.0-32.9, and 3.44 (95% CI 1.67-7.09) for obese men with BMI > or = 33 compared with lean men with BMI < 23.0. Among men > or = 65 years of age, the association between BMI and risk of coronary heart disease was much weaker. However, in this age group, the waist-to-hip ratio was a much stronger predictor of risk (relative risk = 2.76, 95% CI 1.22-6.23 between extreme quintiles). These results suggest that for younger men, obesity, independent of fat distribution, is a strong risk factor for coronary heart disease. For older men, measures of fat distribution may be better than body mass index at predicting risk of coronary disease.


RESULTS: We found a strong positive association between overall obesity as measured by body mass index (BMI) and risk of diabetes. Men with a BMI of > or = 35 kg/m2 had a multivariate RR of 42.1 (95% confidence interval [CI] 22.0-80.6) compared with men with a BMI < 23.0 kg/m2. BMI at age 21 and absolute weight gain throughout adulthood were also significant independent risk factors for diabetes. Fat distribution, measured by waist-to-hip ratio (WHR), was a good predictor of diabetes only among the top 5%, while waist circumference was positively associated with the risk of diabetes among the top 20% of the cohort. ----------------------------------------------------------------- RECENT FINDINGS: Current epidemiologic evidence suggests that waist circumference and waist-hip ratio, as indicators of abdominal adiposity, are positively related to coronary heart disease in men and women independently of body mass index and conventional coronary heart disease risk factors. But the magnitude and shape of the associations for these abdominal adiposity indices varied with adjustments for mediating and confounding factors. Interestingly, hip waist circumference was inversely associated with coronary heart disease after adjusting for waist circumference. Because waist and hips are positively correlated but have separate and opposite associations with coronary disease, using waist circumference alone may provide underestimated risk estimate if hip girth is not accounted for in the calculation of this risk. ----------------------------------------------------------------- Abstract Obesity is an established risk factor for non-insulin-dependent diabetes mellitus (NIDDM). Anthropometric measures of overall and central obesity as predictors of NIDDM risk have not been as well studied, especially in women. Among 43,581 women enrolled in the Nurses' Health Study who in 1986 provided waist, hip, and weight information and who were initially free from diabetes and other major chronic diseases, NIDDM incidence was followed from 1986 to 1994. After adjustment for age, family history of diabetes, smoking, exercise, and several dietary factors, the relative risk of NIDDM for the 90th percentile of body mass index (BMI) (weight (kg)/height (m)2) (BMI = 29.9) versus the 10th percentile (BMI = 20.1) was 11.2 (95% confidence interval (CI) 7.9-15.9). Controlling for BMI and other potentially confounding factors, the relative risk for the 90th percentile of waist: hip ratio (WHR) (WHR = 0.86) versus the 10th percentile (WHR = 0.70) was 3.1 (95% CI 2.3-4.1), and the relative risk for the 90th percentile of waist circumference (36.2 inches or 92 cm) versus the 10th percentile (26.2 inches or 67 cm) was 5.1 (95% CI 2.9-8.9). BMI, WHR, and waist circumference are powerful independent predictors of NIDDM in US women. Measurement of BMI and waist circumference (with or without hip circumference) are potentially useful tools for clinicians in counseling patients regarding NIDDM risk and risk reduction.

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