Women Give Weight Study a Pounding
At 5 feet, 7 inches and 127 pounds, Sarah Cooper is so thin that co-workers nicknamed her Olive Oyl. Naturally, then, she was startled to discover that according to a study released 10 days ago, her risk of dying is 20% higher than that of a woman the same age and height who is a few pounds lighter.
“Wow, it’s pretty amusing that even I bombed out,” Cooper said, referring to the scale of mortality and weight developed by the researchers.
The 37-year-old La Habra resident was not alone in her dismay at the heavily publicized Harvard Medical School study of more than 100,000 middle-aged female nurses, which included the zinger that the “lowest mortality rate was observed among women who weighed at least 15% less than the U.S. average.”
Reacting to that news, many women expressed frustration that the ideal weight appears to be an ever-receding goal, about as attainable as the pot at the end of a rainbow. And given American culture’s sometimes dangerous and often inane idealization of slimness, it seemed that for Harvard physicians to promote the same image was to heap insult upon injury.
Although many experts said the study was perfectly sound and much welcome, especially because one in three Americans is obese, some researchers criticized the study, even saying it was irresponsible for not paying more attention to body shape and the ratio of fat to muscle.
They cite previous work suggesting that lower body fat in “pear-shaped” people is less dangerous than upper body fat, not to mention muscular, physically active people who may be above the ideal weight but are probably healthier than most.
“Not all fat is equal,” said Judith S. Stern, a UC Davis nutritionist who headed an Institute of Medicine study of obesity that was released last spring. “If your weight was lower-body weight, and you had no family history of heart disease, you may not need to focus so much” on the study’s optimum weights.
Kelly Brownell, a psychologist and director of the Yale Center for Eating and Weight Disorders, does not criticize the study, but is concerned that some people may take a “be skinny at all costs” message from it. “In some ways, it’s bad news,” he said. “There’s already tremendous pressure on people to be lean, and this creates even more.”
The recent outbreak of anxious misunderstanding reflects a basic quandary of life in the Era of the Worried Well: translating masses of data from elaborate population studies into simple lessons to live by.
To a researcher steeped in statistics, the Harvard study’s finding that a 5-foot, 5-inch woman minimized her death risk by weighing 119 pounds or less is a useful abstraction. But to a woman hoping to maximize her health and longevity, the very precision of that conclusion appeared to give it the force of doctor’s orders to lose weight--or else.
“Should a middle-aged woman keep losing weight until she’s 15% less than the average? Certainly not,” Stern said. “What the study suggests is that a person might be healthier if some weight is lost.”
The Harvard study, published in the New England Journal of Medicine, was directed by Dr. JoAnn E. Manson, an endocrinologist who is co-director of the Women’s Health Center at the Brigham and Women’s Hospital in Boston.
Delving into a continuous health survey of 115,195 nurses who were 30 to 55 years old when the study began in 1976, Manson and her co-workers found that 4,726 had died. Predictably, the great majority of deaths were among the oldest women.
Next, the researchers sorted all the women into seven weight categories ranging from very thin to morbidly obese. And, to highlight the effects of body weight per se, they focused on women who neither smoked nor gained a lot of weight since early adulthood.
They found that compared with the thinnest women, those who weighed successively more had higher mortality rates. A 5-foot-5 woman’s added mortality risk was 20% at 122 pounds; 30% at about 140 pounds; 60% at 170 pounds, and 100%, or twice the mortality risk, at 180 pounds. “Even women with average weights had higher mortality” than the skinniest women, the researchers concluded.
Although the study has generated much debate over the dangers of being moderately heavy or even average in weight, it has firmly settled one key issue. In previous research, the thinnest people generally had a higher death rate than those of moderate weight. That raised the possibility that skinniness was unhealthy. But Manson and co-workers showed that observation to be largely the result of smoking, which lowers weight and causes death.
So far, so good. But when non-scientists try to use precise study data to understand their own chances of survival, it gets puzzling.
Cooper is among the women seemingly penalized by the study’s statistical categories. If she weighed just 4 pounds less, she would fall into the thinnest group and thus lose the extra 20% mortality risk she is so worried about. Yet it makes no scientific or common sense that she would get so much benefit by changing so little.
Similarly, some women may be misclassified because of their shape. Previous studies have found that weight built up around the belly (the so-called apple shape) contributes more strongly to heart disease than weight around the hips and thighs (the pear shape).
To be sure, the Harvard study found that the apple shape was somewhat more associated with heart disease than the pear shape, but the data was limited to the study’s last six years, leaving the question partly open.
Manson disagreed with the assumption that some shapes are safer than others. “We don’t have evidence that lower-body obesity is safe,” she said. “It would be misleading to suggest that if you’re overweight and you’re pear-shaped that you don’t need to lose weight.”
Because muscle weighs more than fat, a lean muscular woman might also be assigned an inflated death risk by the Harvard study, even though medical researchers believe that a high muscle-to-fat ratio, usually the result of physical activity, indicates good health.
Deborah Praver, a Los Angeles aerobics instructor, said she is “almost 5-foot-2” and weighs 127 pounds. Accordingly, she has a 30% increased mortality risk. Yet she works out two to four hours a day, six days a week. Her body-fat content rivals that of Shredded Wheat.
The researchers “don’t talk enough about fat-free weight,” Praver said. “In terms of disease prevention, fat is the problem, not muscle.” Although she is relatively heavy, she said the last dress she bought was Size 2. “Muscle takes up less space than fat,” she said.
Much of the confusion involves the concept of risk. The 20% increase in mortality ascribed to slim women such as Cooper may sound like an immediate, substantial threat. But the risk that a nonsmoking young or middle-aged woman will die in a given year is so small that a 20% rise verges on the imponderable. The jump in odds translates roughly to a rise from 10 in 10,000 to 12 in 10,000.
Moreover, it turns out that the somewhat notorious 20% figure is not statistically significant, said epidemiologist Susan E. Hankinson, a co-author of the study. That does not mean that the figure is meaningless, she hastened to add, only that the mathematical techniques the researchers were compelled to use give it a misleading precision.
In reality, the added risk conferred by a small amount of excess weight may be less than 20%. Or, for that matter, it may be more. At the moment, 20% is the best approximation the researchers have until they collect more data.
In fact, the middle range of weights is a statistical gray area. Only near the extremes of weight do the researchers’ statistics attain real significance, such as when that 5-foot-5 woman weighs 160.
Still, the added risk burden became vividly apparent when the researchers focused exclusively on heart disease, which is believed to be directly influenced by body fat content. Manson and colleagues found that a woman who gained 40 or more pounds since early adulthood was seven times more likely to die of heart disease than a woman the same age whose weight had remained stable.
Dr. Rena Wing, a psychiatrist and obesity expert at the University of Pittsburgh Medical School, suggests that lay people disregard the finicky statistics and focus on the big picture.
“It’s not as though there’s this magic number when all of a sudden there’s a change in risk,” Wing said of the relationship between body weight and mortality. “Rather, the risk goes up gradually, and any decrease in excess weight would be helpful to people.”
Manson said that perhaps the most important finding pertained not to losing weight but to keeping it off: The lowest death rate of all was among middle-aged women who gained no more than 20 pounds since young adulthood. “We feel that a weight gain of 10 to 15 pounds in early adulthood should serve as an early warning sign,” Manson said.
The idea that such weight gain in middle age increases health risks goes against current federal height-weight guidelines, which incorporate an added 15 pounds or so in middle age. But because other researchers have also lately called attention to the apparent risks of middle-aged spread, the federal guidelines are being revised and are expected to disallow that additional weight.
Dr. David Williamson, an epidemiologist at the U.S. Centers for Disease Control and Prevention, advised against concentrating on pounds and survival odds. Rather, he emphasized healthful habits: don’t smoke, walk plenty, eat wisely, drink moderately if at all, and wear a seat belt. “That’s what we should all be doing, regardless of our body weight,” he said.
In any event, micromanaging one’s health is a practice guaranteed to fail for some people. After all, not even the thinnest people have a zero mortality rate.
Dr. Kenneth Rothman, editor in chief of the journal Epidemiology, acknowledged the difficulty of converting public health data into personal health information. “Epidemiology cannot tell you how to live,” he said. “It can only tell you what the consequences of living a certain way might be.”
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Suggested Weights
Proposed federal guidelines for women and men no longer condone adding pounds in middle and late life. Recommended weights are shown below, with small-boned women at the lower range, big-boned men at the upper.
Height: Weight
5’0”: 97-128
5’1”: 101-132
5’2”: 104-137
5’3”: 107-141
5’4”: 111-146
5’5”: 114-150
5’6”: 118-155
5’7”: 121-160
5’8”: 125-164
5’9”: 129-169
5’10”: 132-174
5’11”: 136-179
6’0”: 140-184
6’1”: 144-189
6’2”: 148-195
6’3”: 152-200
6’4”: 156-205
6’5”: 160-211
6’6”: 164-216
Sources: U.S. Department of Health and Human Services, U.S. Department of Agriculture
