This week’s contribution from “lifestyle epidemiology” was the report — from a huge study of 359,387 participants from nine countries in Europe — that spare tires, love handles, and bulges (the kind you battle) just ain’t good for you. The scientific term for this term is “abdominal adiposity.” Thus, the title of the paper, General and abdominal adiposity and risk of death in Europe (N Engl J Med. 2008;359:2105-20), by T. Pischon and 46 other authors. This is also related to the concept that being shaped like a pear is healthier than being shaped like an apple. Apples, beware!
Once upon a time, nutritional epidemiologists and other anthropometric scientists thought that the measure of a man (or woman) was the BMI — the body mass index. The body mass index is computed by dividing a person’s weight in kilograms (W) by the square of height in meters (H): BMI = W ÷ H2. For weight in pounds and height in inches, the formula is BMI = 703.07 x W ÷ H2. Thus, the existence of BMI tables; online programs for automatically computing your BMI by inputting your height and weight; the NCHS/CDC/NIH/American standard medical categories of BMI:
Underweight = <18.5
Normal weight = 18.5-24.9
Overweight = 25-29.9
Obesity = BMI of 30 or greater;
and the voluminous medical literature showing that (1) overweight and obesity are increasing problems in the United States, the United Kingdom, much of the industrialized world and developing world, and (2) being overweight is bad for your health and being obese is much worse.· Indeed, it seems that as BMI increases upward from normal weight, not only are there monotonically increased risks of mortality and cardiovascular disease, there are also positive associations with dementia, cancers of the esophagus and gastric cardia (the gastroesophageal junction adjacent to the esophagus), and breast cancer.
To measure abdominal adiposity —appleness, if you will — in their New England Journal study, Pischon et al. measured waist circumference and waist-to-hip ratio. The 350,000+ participants were followed up for about ten years and 14,723 died. The authors reported that, “after adjustment for BMI, waist circumference and waist-to-hip ratio were strongly associated with the risk of death.” The relative risk among men with waist circumferences above the 95th percentile (>102.6 cm) was 2.1; the relative risk among women with waist circumferences·above the 95th percentile (>88.9 cm) was 1.8. For men with waist-to-hip ratios above the 95th percentile (>0.98), the relative risk of death was 1.7; for women with waist to hip ratios above the 95th percentile (>0.84), the relative risk was 1.5. The authors point out that even men and women with low-risk BMI’s had a relatively high probability of dying if their waist circumference or waist-to-hip ratio was high.
As with body mass index, there’s a rather large medical literature on abdominal adiposity and its association with health. It’s related to coronary heart disease, pulmonary function, insulin resistance, type 2 diabetes, gallstone disease, and metabolic syndrome. And a time trend study of NCHS’s National Health and Nutrition Examination Surveys (NHANES) between 1960 and 2000 shows an increase in the prevalence of abdominal obesity in the United States, which has “…ominous public health implications across the entire population, particularly among normal weight subjects.” But cheer up. (Or not.) Evidence suggests that exercise does reduce abdominal adiposity.
Those of you with a more practical, activist frame of mind may be interested in The Ashwell Shape Chart. In 1995 the British Medical Journal (BMJ) published a paper by Lean, Han & Morrison arguing that waist circumference — rather than BMI — could be used in health promotion programs to identify individuals who should seek and be offered weight management. Men with waist circumference >/=94 cm and women with waist circumference >/=80 cm should gain no further weight; men with waist circumference >/=102 cm and women with waist circumference >/=88 cm should reduce their weight. In another paper in the BMJ in 1995 Han, van Leer, Seidell, & Lean reported that larger waist circumferences did identify people with increased prevalences of cardiovascular risks (i.e., high risk total plasma cholesterol concentrations, high density lipoprotein cholesterol concentrations, and blood pressures) in a cross-sectional study. In true BMJ fashion, this naturally resulted in the spontaneous generation of a multitude of Letters to the Editor, three of which were: “Ratio of waist circumference to height may be better indicator of need for weight management” by Ashwell & Lejeune; “Ratio of waist circumference to height is strong predictor of intra-abdominal fat” by Ashwell, Cole & Dixon; and “Ratio of waist circumference to height is better predictor of death than body mass index” by Cox & Whichelow. In the first letter the authors·used data from the 1992 health survey to show that the ratio of waist circumference to height was more highly correlated with the risk of coronary heart disease than any other anthropometric measure in both men and women — and much more highly than BMI. In the second letter, the authors used computed tomography data to show that “the ratio of waist circumference to height is the best simple anthropometric predictor of intra-abdominal fat in men and women.” In the third letter, the authors used data from a prospective longitudinal follow-up of British adults to establish that, “there was a linear trend with the ratio of waist circumference to height for both all cause mortality and cardiovascular mortality in women and for cardiovascular mortality in men.” There was, however, no consistent trend observed for body mass index.
The first author of two of these BMJ letters and creator of the Ashwell Shape Chart mentioned above is Dr. Margaret Ashwell. Dr. Ashwell·is a British nutrition researcher who has taken the argument that the ratio of waist circumference to height is superior to BMI to its logical conclusions, both scientifically, in the form of journal articles, and practically, in the form of the Ashwell Shape Chart.
I would love to discuss these issues in more detail, but I’m still having computer problems. I thought I had fixed my wireless router, but it keeps semi-crashing, and I’m afraid it’s going to crash completely before I post this article. For an iconoclastic, more critical viewpoint on the BMI, obesity, etc, check out the series of articles by Patrick Basham and John Lui here, here, here, here, here, here, here, here, and elsewhere on Spiked Online. I’d be interested in hearing your opinions.