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Gaining Time

Over time, weight takes an upward drift, says study

WEDNESDAY, Nov. 21, 2001 (HealthDayNews) -- A study at the University of Michigan Institute for Social Research confirms what most of us suspected: Many of us are getting a little fatter every year, but relatively few of us dramatically change shape over time.

Frank Stafford, an economist who leads the Panel Study of Income Dynamics at the Institute, analyzed weights of more than 10,000 adults over a 13-year period, from 1986 to 1999.

He concluded that 51 percent of men who were of average weight in 1986 stayed essentially the same, 27 percent gained a substantial amount of weight and about 21 percent lost a lot of weight. In the beginning of the study, mid-range weight averaged 175 pounds for a 5-foot-10-inch man. At the upper limit were men who weighed 210 pounds.

The same trend held true for women. About 55 percent of women who were of average weight in 1986 were still that way in 1999, 28 percent had gained a substantial amount and 17 percent had lost a substantial amount. In the beginning, average was about 150 pounds for a 5-foot-5-inch woman. The high-weight range was 180 pounds for the same height.

But even among those whose weight stayed about the same, there was an upward weight drift, with the median body mass index rising from 24.3 in 1986 to 25.9 in 1999. A BMI of 24 for a 5-foot-5-inch woman means she weighs 144 pounds; a BMI of 26 puts her at 156 pounds.

So why should an economist care? Stafford was looking at weight as it relates to death rate and the demand for health care, and he says at least four issues are worth more study:

  • What the government says is a healthy weight doesn't seem to reflect mortality -- at least at midlife. The study indicated that men and women who were somewhat overweight according to federal guidelines had the lowest risk of dying during their mid-30s through their mid-50s.
  • Being underweight appears to be riskier than being overweight for African-Americans. Especially in the case of men, there is a substantially greater risk of death for black men who are thinner than average.
  • There is a link between the weight of the grandmother and her grandchildren that is as strong or stronger than the link between the weights of parents and their children. An overweight grandmother is likely to have overweight grandchildren, and a thin grandma probably has thin grandchildren.
  • One-fifth of children between the ages of 2 and 12 are overweight; another 14 percent are at risk of moving into that category. Boys are chubbier, with 39 percent of them falling into one of the overweight categories compared to 28 percent of girls.

Stafford's research also linked body mass increases with net worth and concluded that, as a general rule, as body mass increases, so also does household wealth. "That's understandable, since people often gain both weight and net worth as part of the aging process," he says.

But another economist who is examining the link between weight and income says that, at least in the case of white women, the fatter-richer idea appears not to be true.

John Cawley, a Cornell University researcher, found in a study he did last year that women who weighed 65 pounds more than average in a sample of 1,442 white female workers earned about 7 percent less than their slimmer colleagues who had similar education and work experience.

Cawley says that this weight-wage discrepancy did not hold true for Hispanic and African-American working women, and it wasn't true for men of any race. And he couldn't find any conclusive evidence that this richer-fatter phenomenon was linked to discrimination in either hiring or promotion.

But it did appear to be linked to how women see themselves. White women report more negative connotations associated with their weight than do men or women of other races. "It could have something to do with self-esteem," Cawley speculated.

Cawley, an economist and an assistant professor of policy analysis and management at Cornell, says his findings could be economically important because the percentage of women who meet the clinical definition of obesity has risen from 15 percent in 1980 to 23 percent in 1990 to 26 percent in 1999.

What To Do

The USDA Food and Nutrition Center provides a wealth of information on weight control, including tools to analyze your body mass index.

If you're concerned about the cost of being overweight, the National Institutes of Health has examined that extensively. This agency also provides a lot of weight-control information specifically aimed at African-Americans . And here's a helpful chart on the BMI levels.

SOURCES: Interviews with Frank Stafford, Ph.D., Director of Income Dynamics, University of Michigan Institute for Social Research; John Cawley, Ph.D., assistant professor of economics, Cornell University; information from the Panel Study of Income Dynamics at the Institute
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