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.Besides cigarette smoking, two other risk fac-tors that have received insufficient attention in health education programsare physical exercise and overweight.Although interest in physical exercise has a long history, perceptionsof its benefits for healthy persons have undergone periodic shifts.Through-out the nineteenth century physical exercise was believed to instill moralvalues and counterbalance the evils of urban life.During the early twenti-eth century, exercise was recognized as an aid in weight control, but wasconsidered less important than caloric intake.After mid-century, the de-cline in strenuous physical exercise due to workplace changes and the auto-mobile has led to the recognition of the health benefits of physical exercisefor cardiovascular functioning, circulation, muscle tone, joint mobility, andweight control.68Research on the relationship between physical activity and coronaryheart disease was first undertaken about mid-century and became a com-ponent of risk-factor research.A 1990 analysis of a number of studies founda dose-response relationship: persons with the highest physical activity lev-els had the lowest coronary heart disease rates, persons with the lowestactivity levels had the highest rates, and persons with moderate activitylevels had rates between the two extremes.The review also found that therelationship was stronger in the studies judged to be methodologically su-perior.However, the findings of practically all studies of physical activityare affected by the tendency of persons in poorer health to select sedentaryoccupations and avoid vigorous exercise.Given the small number of casesof coronary heart disease in most studies, even a few such persons in asample can affect the findings.At least part of the statistical correlationbetween physical activity and coronary heart disease results from the self-selection of persons into high and low physical activity groups based ontheir preexisting health status.69Overweight became one of the most rapidly growing health prob-lems toward the end of the twentieth century.Between 1960 62 and 198894, the age-adjusted proportion of all Americans ages 20 74 who weresignificantly overweight rose from 24% to 35%, with increases occurringfor both sexes and all age groups.Significant overweight was defined as abody mass index in the top 15% of the population using a distributionbased on a sample of men and women ages 20 29 in a 1976 80 nationalsurvey.Among children, the age adjusted proportion of boys and girls whowere defined as overweight increased from 5% in 1963 70 to 14% in 198894 of those ages 6 11 and from 5% to 12% of those ages 12 17, using amore restricted definition of overweight.70Dietary Recommendations and Guidelines 339The adverse health consequences of obesity have been most convinc-ingly demonstrated by many life insurance longitudinal studies.These areamong the most impressive studies of risk factors ever conducted: theyhave very large samples, long time durations, and statistically valid meth-ods of selecting representative samples from the population of life insur-ance policyholders.The policyholders were given medical examinationsand found to be in good health when they purchased insurance and there-fore were less likely to have unrelated illnesses that affected their mortalityrates.They were more homogeneous than the general population with re-gard to socio-economic status, which reduced differences in that importantdeterminant of mortality.Policyholders are rarely lost to follow-up over thecourse of the study because of the need to present evidence of death.Thelife insurance mortality studies before mid-century are especially valuablebecause few treatments were available to extend the lifespans of policyhold-ers who died of causes related to obesity.A study of 25,998 overweight men and 24,901 overweight womenwho purchased ordinary life insurance policies from the Metropolitan LifeInsurance Company between 1925 and 1934 followed them until 1950,an average duration of twenty years.During the period 3,713 deaths oc-curred among the men and 2,687 among the women.The policyholderswere sufficiently overweight to be sold substandard insurance policies buthad no other impairments with regard to physical condition, medical his-tory, or occupation.This is an extremely important condition because itreduces the probability that preexisting illnesses could have raised theirmortality rates.Using age at issuance, the mortality rates of the overweightpolicyholders compared to policyholders who purchased standard policieswere as follows: 80% higher for men ages 20 29; 69% higher for men ages30 39; 52% higher for men ages 40 49; and 31% higher for men ages 5059.Among women the overweight groups had mortality rates that were 34to 52% higher, but no age trends were evident.The higher death rates fromsome specific diseases for men and women respectively were as follows:diabetes mellitus 3.8 and 3.7 times standard risks; coronary and organicheart disease 1.4 and 1.8 times standard risks; stroke 1.6 and 1.6 timestandard risks; and chronic nephritis 1.9 and 2.1 times standard risks.Theoverweight policyholders were at no greater risk of dying from cancer orpneumonia.A 1997 review of more recent studies not conducted by thelife insurance industry also found a strong relationship between obesityand total and cardiovascular disease mortality rates.71Many studies have found a strong dose-response relationship betweenbody weight and mortality rates.The 1959 Build and Blood Pressure Study340 Risk Factors and Coronary Heart Diseaseof the Society of Actuaries examined several million men and women whopurchased ordinary life insurance policies from 26 large life insurance com-panies from 1935 to 1953 and followed them to the anniversary of theirpolicies in 1954.Mortality rates of overweight policyholders with no otherknown impairments that affected their insurability were compared to themortality rates of all standard risk policyholders.By age at policy issuance,men 10% above average weight had a 3% higher mortality rate at ages 1539 and an 8% higher at ages 40 69.Men 20% above average weight had a15% higher mortality rate at all ages.Those 30% above average weight hada 30% higher mortality rate at all ages.Women 10% above average weighthad no higher mortality rate, those 20% above average weight had a 6%higher mortality rate for those ages 15 39 and 15% higher for those ages40 69, and those 30% above average weight had a 12% higher mortalityrate for those ages 15 39 and 25% higher for those ages 40 69 [ Pobierz całość w formacie PDF ]