Ten percent.

Losing that amount of body weight is what a growing number of studies suggest can significantly improve your health if you are overweight or obese.

It doesn't sound like much and, in fact, it's far less than the lofty goals that most overweight people set for themselves. But studies consistently show that trimming 10 percent of your body weight -- that's 15 pounds for someone who weighs 150; 20 pounds for a person whose scale reads 200 and 30 pounds for a 300-pounder -- can make a big health difference.

"I encourage my patients to try to first lose 10 percent of their body weight," said Rena Wing, professor of psychiatry and human behavior at Brown University in Providence and co-founder of the National Weight Control Registry, a group of 4,000 people who have lost an average of 70 pounds and kept it off for five years. "If after doing that, if they still want to pursue more, then they can. But at least work on doing that 10 percent and keep it off."

Among the health benefits from shedding this amount of weight are:

Better blood pressure. Studies suggest that every 1 percent reduction in body weight translates to a drop of about one millimeter of mercury in systolic blood pressure (the top number in a blood pressure reading, taken when the heart contracts) and about two millimeters in diastolic blood pressure (the bottom number, measuring pressure when the heart relaxes between beats.) So losing 10 percent of your body weight could add up to a 10- to 20-millimeter drop in blood pressure, which could mean a reduction or even elimination of the need for blood pressure medication.

Improved blood cholesterol levels. Numerous trials show that modest amounts of weight loss improve levels of various blood fats, from decreasing dangerous triglyceride levels and low density lipoprotein (LDL) to increasing protective cholesterol or high density lipoprotein (HDL.)

Decreased risk for diabetes. The Diabetes Prevention Program, a large, federally funded study of more than 3,000 overweight and obese people, examined the benefits of losing just 7 percent of body weight and found that doing so produced a 58 percent reduction in diabetes risk for people who were on the cusp developing diabetes.

Better sex. According to a recent study by Martin Binks, director of behavioral health at the Duke University Diet and Fitness Center, subjects' feelings of sexual attractiveness, sexual desire, enjoyment of sexual activity, comfort at being seen undressed and sexual performance all improved with a 10 percent loss in body weight. Binks and his colleagues drew their conclusions from a two-year trial of 100 very obese men and women with an average body mass index of 40, roughly equal to someone 5 feet 7 inches tall weighing 255 pounds.

"Most of the improvements seem to happen around the 10 percent mark," said Binks, who presented his findings at the annual meeting of the North American Association for the Study of Obesity in Vancouver. "We see medical improvements at that point, a lot of physical health improvements, and sexual quality of life follows a similar pattern."

There's a clear message that "you don't have to be some ideal weight to have a happy and healthy sexual life," Binks said. "Often expectations of weight loss are unrealistically high. I encourage people to focus on the quality-of-life factors, and this is one of them. They may experience a level of reward that helps them move forward in sticking with a healthy lifestyle."

Evidence for the power of achieving a 10 percent drop in body weight has also prompted Shape-up America!, a nonprofit group founded by former U.S. Surgeon General C. Everett Koop, to develop a free, online program called "Drop 10." (www.shapeup.org/shape/sud10index.html)

"People are daunted by saying, 'I have to lose 100 pounds,' " said Barbara Moore, executive director of Shape-Up America! "But losing 10 percent of your body weight is something they can accomplish."

Here's what you need to know if you decide to lose 10 percent of your body weight:

Keep it slow, but steady. Quick weight loss is what most people dream of and what is dangled by many diet books and weight loss programs. But a comprehensive report on weight loss issued by the National Heart, Lung, and Blood Institute notes that "a reasonable time line for a 10 percent reduction in body weight is six months."

Get into negative balance. To lose weight, you need to achieve a calorie deficit. For people with a body mass index of 27 to 35 -- that's 170 to 225 pounds for someone who is 5 feet 7 inches tall -- plan on decreasing calories by 300 to 500 per day. That works out to losing about half a pound to a pound per week; over six months, that equals 10 percent of body weight. For heftier folks, a good goal might be cutting 500 to 1,000 calories daily. That adds up to a one- to two-pound weight loss per week, or about a 10 percent loss of body weight in six months.

No need to just reduce your food intake. Achieve your negative calorie balance with a combination of physical activity and fewer calories. So to reach a 500-calorie deficit, you might eat 250 fewer calories and increase physical activity by 250 calories. For example, switch from large fries at McDonald's to small and you save 290 calories. Walk briskly for 45 minutes and burn about 250 calories. And you don't have to do that walking all at once; 10 minutes at a time produces the same results -- another example of the power of 10.

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