What You Can Change _. And What You Can't - Martin E. Seligman [157]
Substantial Obesity (30 to 100 percent above “ideal “weight): Choosing the low cut point is the most difficult and controversial part of distilling this large literature. Thirty percent overweight looks to me to be approximately the point at which some danger begins. The “Pooling Project” combined data for 12,381 men from eight different American populations who had been followed for five to ten years. Looking at first heart attack, the inflection point seems to be at 30 percent over “ideal” weight. This is a conservative estimate, however, since it can be argued from these data sets that there is no increase at all in coronary risk with weight. See The Pooling Research Project Research Group, “Relationship of Blood Pressure, Serum Cholesterol, Smoking Habit, Relative Weight and ECG Abnormality to Incidences of Major Coronary Events: Final Report of the Pooling Project,” Journal of Chronic Diseases 31 (1978): 201–306; E. Barrett-Connor, “Obesity, Atherosclerosis, and Coronary Artery Disease,” Annals of Internal Medicine 103 (1985): 1010–19.
The other essential source is Ancel Keys’s curve fitting of more than a dozen large-scale studies of body mass and coronary heart disease. His curves show two inflection points: one at the 30 percent overweight locus and the other at underweight. Importantly, the direction of the slope with mild overweight (o to 30 percent) is downward, with more weight up to about 30 percent associated with less risk. See A. Keys, “Overweight, Obesity, Coronary Heart Disease.”
See also E. Hammond and L. Garfinkel, “Coronary Heart Disease, Stroke, and Aortic Aneurysm,” Archives of Environmental Health 19 (1969): 167–82. This is a landmark prospective study of one million people, and it shows increased risk with body weight. But the body weight at which the risk begins is in the upper 20 percent of the population, which seems to correspond to about the 30 percent overweight cut point.
One consoling note to people in this category: This amount of overweight probably does put you at risk in and of itself. Overweight correlates with high blood pressure and serum cholesterol. If your blood pressure is normal, if your cholesterol is normal, if you exercise moderately, and if you don’t smoke, your risk of heart attack is not increased by being overweight. See the classic A. Keys, C. Aravanis, H. Blackburn, et al., “Coronary Heart Disease: Overweight and Obesity as Risk Factors,” Annals of Internal Medicine 77 (1972): 15–27.
Diabetes mellitus, in contrast to coronary heart disease, presents a clearer picture of risk with moderate overweight. In one prospective study, risk went up 1,000 percent with moderate obesity and 3,000 percent with 45 percent obesity. See K. Westlund and R. Nicholaysen, “Ten-Year Mortality and Morbidity Related to Serum Cholesterol,” Scandinavian Journal of Clinical and Laboratory Investigations 30 (supplement 127) (1972), 3. See also A. Rimm, L. Werner, B. Van Yserloo, and R. Bernstein, “Relationship of Obesity and Disease in 73,532 Weight-Conscious Women,” Public Health Reports 90 (1975): 44–51. My conclusion is that if diabetes runs in your family, you should be more attentive to overweight as a risk factor than if heart disease runs in your family.
Mild to Moderate Overweight (10 to 30 percent above “ideal” weight): I have chosen my language carefully here—“possibly associated with a marginal increase in mortality”—because for every study that shows some health risk in this category, there is at least one that shows no health risk.
The thrust of the Keys and Barrett-Connor reviews is that there is little or no more heart-attack incidence in this range. Indeed, these people may be at lower risk