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When it comes to nutrition, it's easy to spend a lot of time worrying about what to eat. But how much you eat puts as much of a stamp on your long-term health as picking the right kind of fat or choosing the right mix of vitamins.
How much you weigh (in relation to your height), your waist size, and how much weight you've gained since your mid-20s strongly influence your chances of:
•dying early,
•having, or dying from, a heart attack, stroke, or other type of cardiovascular disease,
•developing diabetes,
•developing cancer of the colon, kidney, breast, or endometrium,
•having arthritis,
•developing gallstones,
•being infertile,
•developing asthma as an adult,
•snoring or suffering from sleep apnea,
•developing cataracts, or
•having a poorer quality of life.
Although researchers are quibbling about just how many people die each year as a direct cause of excess weight and what it costs our health-care system, excess weight takes an enormous toll—all the more worrisome, given that we are in the midst of an obesity epidemic.
If your weight is in the healthy range and isn't more than 10 pounds over what you weighed when you turned 21, great. Keeping it there—and keeping it steady—by watching what you eat and exercising will limit your risk of developing one or more of the chronic conditions noted above. If you are overweight, doing whatever you can to prevent gaining more weight is a critical first step. Then, when you're ready, shedding some pounds and keeping them off will be important steps to better health.
What's a Healthy Weight? Body Mass Index (BMI) Defined
Although nutrition experts still debate the precise limits of what constitutes a healthy weight, there's a good working definition based on the ratio of weight to height. This ratio, called the body mass index (or BMI for short), takes into account the fact that taller people have more tissue than shorter people, and so tend to weigh more.
Dozens of studies that have included more than a million adults have shown that a body mass index above 25 increases the chances of dying early, mainly from heart disease or cancer, and that a body mass index above 30 dramatically increases the chances. Based on this consistent evidence, a healthy weight is one that equates with a body mass index less than 25. By convention, overweight is defined as a body mass index of 25 to 29.9, and obesity is defined as a body mass index of 30 or higher.
Nothing magical happens when you cross from 24.9 to 25 or from 29.9 to 30. These are just convenient reference points. Instead, the chances of developing a weight-related health problems increases across the range of weights.
Muscle and bone are more dense than fat, so an athlete or muscular person may have a high body mass index, but not be fat. It's this very thing that makes weight gain during adulthood such an important determinant of weight-related health—few adults add muscle and bone after their early twenties, so nearly all that added weight is fat.
HARVARD - School of Public Health
