The fastest way to lose weight—including fat—is through diet, but heres the hitch: The faster you shed pounds, the more lean body mass you lose. “Thats why its best to lose one to two pounds a week,” says Donald K. Layman, PhD, professor emeritus at the University of Illinois Department of Food Science and Human Nutrition.

According to his research, the diet you choose matters, too. In general, in a high-carb diet, about 70% of the weight you lose is fat and 30% is lean muscle. With a moderate-protein diet, the ratio is 80-to-20 or better—but adding 30 minutes of exercise each day (walk five days a week; do Pilates or yoga, or lift weights on the two other days) will help you lose almost all fat and very little lean muscle, Laymans research shows. “Thats the winning combination,” he says. Heres what else is in the news.

Bariatric surgery
For those who are severely overweight (typically having a BMI of 40 or greater, or 35 or higher with health problems), gastric bypass and banding procedures have been shown to improve—and even cure—type 2 diabetes, hypertension, high cholesterol, and sleep apnea, says Jeffrey Tice, MD, assistant professor of internal medicine at the University of California, San Francisco.

Gastric bypass reroutes the digestive system to bypass much of the stomach and the first section of the small intestine, decreasing the absorption of calories. Banding involves wrapping a small beltlike device around the top of the stomach to limit food intake. Note: There are risks involved with any surgery.

The reason these surgeries are so effective: Patients typically lose about half of their excess weight. A recent study found that obese women who had lost weight with bariatric surgery also reduced their risk of pregnancy-related complications like gestational diabetes and high blood pressure.

Next Page: Liposuction [ pagebreak ]

This fat-removal surgery (docs use a thin surgical instrument to break up fat cells in a particular area, then vacuum out the cells with a suction device) is best for healthy people who have localized fat deposits they want to get rid of—saddlebags, love handles, tummy fat—not those who want to lose lots of weight, says John Canady, MD, president of the American Society of Plastic Surgeons. “If you maintain your weight afterward, the fat loss is permanent.” The average amount of fat thats removed varies.

The newer laser-assisted liposuction produces about the same results, although fewer studies have been done on it. So far, neither lipo procedure has been proven to improve cardiovascular risk factors.

Fat dissolving
Liposuction-like techniques that claim to dissolve fat by injecting a number of different chemicals havent been approved by the Food and Drug Administration. (Some like Kythera Biopharmaceuticalss ATX-101, used for zapping fat deposits under the chin, are aiming for approval.)

“There hasnt been a lot of research demonstrating that they are effective,” Dr. Canady says. A diffferent approach that does look promising: injections that block the receptor for neuropeptide Y, a molecule that enhances the growth of fat. “Weve studied it in mice, and it not only eliminates fat but can prevent metabolic syndrome in those fed a high-fat diet,” says Stephen Baker, MD, DDS, an associate professor of plastic surgery at Georgetown University Hospital.

Most of those fat-burning supplements advertised on the Internet dont work. But a few do. Conjugated linoleic acid (CLA), a polyunsaturated fatty acid found naturally in meat and dairy products, may increase the amount of fat you burn, especially at night.

“Placebo-controlled clinical trials have shown that taking supplements of CLA for six months or more result in about 4.5 pounds of fat loss,” says Dale Schoeller, PhD, a professor of nutritional sciences at the University of Wisconsin in Madison who has studied the substance. And green tea may help with weight loss, according to animal studies, although more research is needed on humans.

Weight-loss Meds
When used with a sensible diet and exercise plan, drugs like orlistat can help you lose an additional 5 to 10 pounds. “Thats not trivial, but its not a huge impact, either—especially if you have a lot of weight to lose,” says Howard Eisenson, MD, executive director of the Duke Diet and Fitness Center.