MadSci Network: Evolution

Re: Short term evolution of human race

Area: Evolution
Posted By: Jim McCarter, MD/PhD Student, Genetics.
Date: Tue Apr 9 22:30:03 1996


Dear Adrian,

To quote from a recent review "Obesity is a major contributor to chronic and costly diseases and disabilities. More than 30% of American adults are obese, and the percentage has been rising for 20 years. A recent estimate placed the direct economic costs of obesity at more than $39.3 billion, or 5.5% of all medical expenditures in the mid-1980s. You are right when you say that the norm weight is increasing in the U.S. Both the median and the mean are going up. An ideal weight, however, does not change. (In other words, just because we Americans are all getting fat doesn't make it ok.)

A Body Mass Index of 25-30 means the person is >20% over their ideal body weight. These people are considered to have Grade 1 obesity, and even this level of extra weight does lead to greater morbidity. Obesity is associated with high blood pressure, high cholesterol, heart disease, stroke, adult onset diabetes, degenerative arthritis, sleep disorders, and cancers of the breast, uterine, cervical, and ovarian in women, and colon and prostate in men.

One paradox is that increased weight leads to morbidity and mortality, yet Americans are living longer. This appears to be due to other improvements in health despite obesity. Infectious diseases are better controlled, some people have stopped smoking, others are obese yet treat their high blood pressure and cholesterol, and therefore prevent immediate cardiovascular disease.

There are web sites on obesity at Weight and bkrentzman

Take care,


ps- Increasing obesity in the U.S. over a few generations really can't be considered "short term evolution of the human race". Evolution requires changes in gene frequency in a population and just because our "phenotype" is bigger doesn't mean our genotype has changed. A better way to characterize obesity is culturally, each Burger King and Pizza Hut ad is a cultural "meme" transmitted over the airwaves and changing our phenotype far more rapidly than evolution can.

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