Is it okay to be overweight? A widely publicized study in the Journal of the American Medical Association in April seemed to answer yes.

Government researchers analyzed large national surveys and concluded that obesity could be linked to about 112,000 deaths annually in the U.S. That's a lot of deaths, but far less than previous estimates. What caused the most shock waves was the finding that people who are slightly or moderately overweight (but not obese) may actually have a lower death rate than those at normal weight. Columnists had a field day, making fun of overzealous government health experts as well as people who have struggled to stay thin. And food-industry groups launched a self-serving ad campaign claiming that some people have been misled about weight.

First of all, what is normal, overweight, or obese? That, of course, is the crux of the matter. The study used the standard ranges based on the body mass index (BMI, a weight-to-height formula). Normal weight is defined as BMI between 18.5 and 25. Overweight is 25 to 30; obese is 30 and above. Accordingly, for someone 5' 8" tall, normal is 122 to 164 pounds; overweight, 165 to 196; and obese, 197 and over. (To figure out your BMI, click here.)

There always has been debate about these numbers and what optimal weight is. Before 1998 the ranges were looser. At 5' 8", overweight didn't begin until 180 pounds. These lines are hard to draw, and this study (as well as some other research) suggests that the normal range may now be too low.

The good news: If the new study is correct, fewer people are dying of obesity-related illnesses than expected, particularly after age 60. One explanation is that things have changed in recent years. In fact, another study in that same issue of JAMA showed that Americans, especially those overweight or obese, are at far lower risk for cardiovascular disease than 20 to 40 years ago because they have lower blood pressure and cholesterol, on average largely thanks to medication and perhaps better diet and much lower smoking rates. Remarkably, overall death rates from heart attacks have been cut in half since 1980.

The bad news: Headlines about these new studies may make some people think it's okay to pack on lots of pounds. However, there's no question that obesity increases the risk of heart attacks, strokes, diabetes, osteoarthritis of the knees and hips, and some cancers, and that it can shorten lives. Diabetes rates are skyrocketing. Obese people who lose weight benefit greatly. The new study looked only at death rates just the tip of the iceberg according to the researchers not at how obesity impairs quality of life and increases disability and health-care costs.

The confusing news: Calculating the adverse effects of overweight/obesity is complex, and this study is not the last word. The Centers for Disease Control and Prevention is still reviewing the new findings, and is not softening its campaign against obesity. The fact is, no one knows how many people die as a result of obesity. Obese people often have a poor diet and are sedentary, so it's hard to tell whether it's obesity itself or these other factors that put them at risk. The health risks of being merely 10 or 20 pounds overweight are especially unclear.

Words to the wise: Your optimal weight depends on many factors notably your fitness level, family history, risk for various diseases, and genes. If you are 5' 8" and weigh 185 pounds, that's overweight. But if you exercise regularly, don't smoke, and are healthy in other respects, you don't need to make big changes. On the other hand, if you have borderline-high blood pressure or blood sugar, or not-so-great cholesterol levels, one of the most important things you can do is lose weight. If you have diabetes or a family history of premature heart disease, this is essential.

For many people, being a little overweight is not a health problem, except that it often leads to greater weight gain. Thanks to medical advances, we are better at treating obese people, thus prolonging their lives. But the cost, in dollars and quality of life, is great.

What's your BMI?