Among those who attended the AHA Scientific Sessions 2003, the prevalence of obesity was notably low, but in the surrounding streets and shops of Orlando, Fla, the picture was very different. The United States is indeed a leader in obesity—a condition now pandemic, with a billion people affected worldwide. The explanation, seemingly, lies in humankind’s hunter-gatherer inheritance, which leaves us ill equipped to deal with today’s abundant diet and sedentary lifestyle. About one third of obese individuals (mainly those with central obesity) develop either type 2 diabetes mellitus or its milder variant, the metabolic syndrome, in which hyperinsulinemia leads to excess cardiovascular risk. We face the prospect that the pandemic, as it gains momentum, will reverse all the population benefits achieved over the past decades through control of hyperlipidemia, hypertension, and tobacco smoking. Indeed, a plenary session was titled “The Obesity Epidemic: Will It Undo the Last 40 Years of Progress?” In it, Dr Scott M. Grundy (Dallas, Tex) summarized the pharmacological strategies for suppressing different components of the metabolic syndrome—hyperlipidemia, prothrombotic state, hypertension. He was hopeful, also, that cardiovascular risk will prove reducible by agents that lessen insulin resistance.
Dr Grundy did not discuss a proposal made in the British Medical Journal last June whereby a daily “polypill” (statin, antihypertensives, folic acid, aspirin), if taken by most men and women over age 55 years, would substantially reduce the population incidence of heart disease and stroke. Though this concept has been widely derided by the medical profession, it received sympathetic mention from Dr Augustus Grant, President of the American Heart Association, in his opening address. The principle is that large gains can be achieved by modest effects in large numbers. Discussing the alarming trend in childhood obesity (prevalence 15% now in US adolescents, coupled with an increase in severity), Dr Stephen R. Daniels (Cincinnati, Ohio) favored a preventive approach on the same principle. Once obesity is established, it is very hard to treat. The aim here would be to reduce the averagebody mass index of children and adolescents by interventions such as reduction of food portion size and greater provision for physical education in schools (in 15 states of the United States, there is at present no requirement for physical education in high schools, despite the fact that in leisure time the children’s physical activity is often near zero). An additional preventive approach would be to focus on children at high risk, such as those with obese parents, low birthweight, or rapid weight gain in the first year. Might new genetic or biochemical markers be helpful? One candidate is adiponectin, a protein from fat cells that enhances insulin sensitivity along with other antiatherogenic effects, with low blood levels being unfavorable. Dr Koji Ohashi and coworkers (Osaka University, Japan) reported a mutation associated with low blood adiponectin levels, independent of body mass index, and an excess of both metabolic syndrome and coronary artery disease.
Once a child has become overweight, he or she is very likely to become an obese adult. In a longitudinal study of children recruited at age 13 and followed up to age 26, Dr Julia Steinberger (University of Minnesota) found that adiposity in adolescence predicted not only obesity but also metabolic syndrome. That early intervention can be effective was suggested in a study by Drs Katie Watts and Daniel Green (University of Western Australia, Perth, Western Australia). In a randomized crossover trial, 35 obese children underwent special programs of exercise lasting 8 weeks and had tests of vascular endothelial function. Even though they did not lose weight (lean muscle replaced fat), flow-mediated vasodilatation improved significantly with exercise. Unfortunately, the benefit quickly disappeared when exercise ceased.
Naturally, at such a congress, the emphasis was on cardiovascular end points. A powerful argument for the population approach to obesity is that coronary artery disease and stroke are just two out of a host of comorbidities.