For the obese, a small loss may be a big victory.

Evidence is building that really heavy people may be able to greatly improve their odds of dodging weight-related illnesses while remaining very heavy.

The secret: Lose just a few pounds. Weight reduction, it appears, is powerful medicine for the large, no matter how seemingly insignificant the dose.

Many obesity experts agree that getting down to a normal size may not be necessary to avoid much of the bad effects of being big. Dropping just 10 or 15 pounds � too little to even miss on many people � can have a surprising and substantial effect on the body processes that obesity disrupts.

If true � and the idea still has some skeptics � this means that at least a partial antidote to the apocalyptic predictions about the obesity epidemic may be within reach, even if people remain vastly overweight by every measure.

“The bad news is people are getting more and more obese,” says Dr. Christie Ballantyne, a cardiologist at Methodist Hospital in Houston. “The good news is losing a modest amount of weight can have really profound health benefits.”

Of course, many big people want to slim down so they will look better. But doctors say the best reason for getting control of weight is to be healthier.

“That is one of the most important public health messages to get out to people,” says Dr. Judith Fradkin, diabetes endocrinology head at the National Institute of Diabetes and Digestive and Kidney Diseases. “The goal should be to become healthy, not become a fashion model. If you move in the right direction even a little bit, that can make a big difference in health.”

That’s good news for people who throw up their hands in defeat because they cannot get down to their ideal weight. Just a loss of 15 pounds for someone 90 pounds too heavy can make a big difference, Fradkin says.

There is little doubt among mainstream experts that obesity is a potentially deadly condition, blamed for about 300,000 deaths annually in the United States alone. For a middle-aged person, it is considered to be about as bad for health as smoking is.

Many experts believe that the real hazard of being overweight is the torrent of hormones and other chemicals pumped out by fat storage cells, which become hyperactive when filled to capacity with fat.

The damaging effects of obesity are obvious on a physical exam. Not every nondiabetic, overweight person has all these abnormalities � which can raise the risk of heart attacks, diabetes and strokes � but many do. The most common:

  * HDL cholesterol, the good variety, is unusually low � below 40 in men and 50 in women � even though the bad LDL is normal.

  * Blood pressure is 130 over 85 or greater.

  * Fasting blood sugar is between 110 and 126.

  * Free-floating fats called triglycerides are over 150.

  * C-reactive protein, a sign of bloodstream inflammation, is high, often over 3.

Experts believe that overactive fat can do all of this, at least in part by making the body less receptive to signals from insulin that tell it to store up energy. As a result, the liver has to produce more insulin, which can be harmful itself at high levels and raises the risk of diabetes.

The benefits of losing just a bit of weight are often apparent in people with a body-mass index well into the obese range � 35 and beyond. Typically, these people are at least 50 pounds overweight and often much more.

In his weight clinic, Ballantyne watched patients whose BMI’s averaged 41. After losing about 7 percent of their weight in a month, most of these ominous signs got substantially better, even though their BMI’s still averaged 38.

Their blood pressure fell to normal. Triglycerides dropped 40 percent back into the healthy range. Inflammation dropped between a quarter and a third. HDL budged upward slightly.

In many cases, the benefits are as big as typically seen with a fistful of pills, says Ballantyne. “You are altering the metabolic functions more profoundly than the weight, which is great news.”

Doctors say people whose weight continues to fall do best, and those who put some of it back on lose part these improvements. Still, they seem much better off having lost and partially regained than never having lost at all.

The biggest questions, though, are how long these improvements last and whether they translate into better survival, as doctors expect they should.

“I think it would probably help them,” says Dr. Xavier Pi-Sunyer, head of obesity research at St. Luke’s Roosevelt Hospital Center in New York City. “But is there good evidence this is so? We don’t have it.”