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Surprise! Ten myths that can trip you up

Nutrition Action Healthletter, Jan-Feb, 2008 by Bonnie Liebman

When it comes to diet and health, everyone's an expert.

Whether the advice comes from your cousin or co-worker, your personal trainer or chiropractor, a magazine or the Internet, what you hear often sounds convincing.

What's more, even well-respected scientists--and their studies--often disagree about how to lose weight, prevent cancer, or protect your heart, bones, brain, or eyes. And that doesn't begin to cover what you see on food labels or in ads.

This month we take on some common misconceptions. And there are plenty more where these came from.

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Here are ten myths that may surprise you.

More Articles of Interest: Can you afford the extras?; Secrets of successful losers; Tackling salt; Legume magic; Fish for Thought?

1 It's okay for older people to be overweight.

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"Extra Pounds May Carry Certain Benefits," ran the front-page headline in The Washington Post last November. A new study, published in the Journal of the American Medical Association, brought news that most people wanted to hear.

In an analysis of nearly 37,000 participants in the National Health and Nutrition Examination Survey, the obese had a higher risk of dying of diabetes, heart disease, and several cancers. However, people who were not quite as heavy--the merely overweight--had no higher risk of dying of cancer or heart disease than people who were normal weight.

What's more, the overweight had a lower risk of dying of diseases like emphysema, pneumonia, tuberculosis, and Alzheimer's disease than those who were normal weight.

"Extra weight means longer life" may make eye-catching headlines. But it's always a suspicious finding.

"When people have underlying chronic diseases that lead to weight loss--diseases like cancer or respiratory or cardiovascular disease--they shift into the lower-weight categories, and that makes leaner people look worse off than the overweight," explains JoAnn Manson of Harvard Medical School and Brigham and Women's Hospital in Boston.

Researchers try to exclude people who are already ill, but it's not easy to do. "It's difficult to account simultaneously for past smoking, pre-existing disease, and weight loss due to underlying disease at the same time," says Manson. "It takes a large study to do that."

In other studies, including the Physicians' Health Study of more than 99,000 men and the Nurses' Health Study of more than 115,000 women, the risk of dying was higher in the overweight. (1,2)

It's not entirely clear why studies disagree, says Manson (see "The Weight Debate," Nutrition Action, October 2005). Perhaps researchers should only look at whether being overweight when you're middle-aged or younger affects your risk of dying when you're older, she suggests.

"Measuring weight at midlife may be a more reliable measure because older people have already lost muscle mass and many have lost weight due to chronic diseases."

Once people are older, it's not so much weight, but how much muscle they've lost and how much fat they've gained, that may matter. In a recent study, older men with the largest arm circumference (a sign of greater muscle mass) and the smallest waists had the lowest risk of dying. (3)

More importantly, the recent study that made headlines says nothing about your risk of getting cancer, heart disease, or diabetes.

"We know that both overweight and obesity increase the risk of many diseases that affect health and quality of life and that markedly increase medical costs," says Manson.

And, for many people, overweight is just a stepping stone on the road to obesity.

"We can't afford to become complacent about the epidemic of overweight and obesity," warns Manson. "We don't want to send the message that you should be overweight to lower your risk of premature death."

(1) Int. J. Obes. 31: 1240, 2007.

(2) N. Engl. J. Med. 333: 677, 1995.

(3) Am. J. Chn. Nutr. 86: 1339, 2007.

2 High-fructose corn syrup is worse for you than ordinary sugar.

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"The Devil's candy," a "sinister invention," "the crack of sweeteners," and "crud" are just some of the names people have given high-fructose corn syrup (HFCS), according to The New York Times. The brewing hysteria has led some companies to brag that they use sugar instead of HFCS, which is now added to soda pop and just about every other food that's sweetened.

The myth got some legs in 2004, when several respected researchers suggested that one cause of the obesity epidemic was the ten-fold jump in high-fructose corn syrup consumption from 1970 to 1990.

"A colleague, George Bray, and I wrote an article in which we speculated about potential harm from HFCS," Barry Popkin, director of the Interdisciplinary Center for Obesity at the University of North Carolina, told us in 2006. "But we really don't think this is a key issue."

It's difficult to see how high-fructose corn syrup--which is roughly half fructose and half glucose--could be much different from ordinary table sugar (sucrose), which is quickly broken down in the body into--you guessed it--half fructose and half glucose. In fact, the acids in soft drinks that contain sucrose break down some of the sucrose right in the can.

Surprise! Ten myths that can trip you up

Nutrition Action Healthletter, Jan-Feb, 2008 by Bonnie Liebman

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