This dual effect helps explain how such drugs cause weight loss. The findings also reinforce the role of serotonin, which regulates emotions, mood and sleep, in affecting the brain's melanocortin system, a key pathway that controls body weight, he said.

Learning how these drugs work, one could potentially target these pathways and avoid the harmful side effects associated with a drug like Fen-Phen while still controlling the feeling of hunger, Elmquist said.

"The goal of pharmaceutical companies is to identify the neurons that are key for body-weight control and within those neurons the key signaling pathways," Elmquist said. "If you could target those, you could have a more effective and safe treatment," he said.

One expert agrees that it may be possible to develop new safe and effective diet drugs, but for use only as a bridge to lifestyle changes.

"This finding really shows us where we can focus our efforts for new therapeutics that target the receptor they have identified as the one that's key in the regulation of food intake," said Philip Smith, director of the Division of Diabetes, Endocrinology and Metabolic Diseases at the National Institute of Diabetes, Digestive and Kidney Diseases.

Smith thinks that these new drugs could target centers of the brain that effect behavior. "The key is what motivates behaviors like overeating and smoking," he said. "Drugs that target the pathways found in this study are likely to target motivational pathways that are involved with serotonin."

But drugs alone aren't the answer to the growing obesity epidemic, Smith said. "The only hope is that we actually modify lifestyle," he said.

"The question is, can we find drugs that will help enable that? Not something that would be a lifetime drug. But just like a nicotine patch, one could imagine a patch that would get you through the hardest part of losing weight so that you could actually change your lifestyle, and you are not constantly fighting the urge to eat," Smith said. "It is lifestyle change that will really make a dent in the obesity epidemic."

More information

The National Institute of Diabetes and Digestive and Kidney Diseases can tell you more about dieting.

Chemotherapy in Childhood Can Bring Adult Heart Woes

 THURSDAY, July 20 (HealthDay News) -- New research provides more evidence that certain chemotherapy drugs can harm the hearts of young people with cancer and cause worsening cardiac problems decades later.

Dutch scientists found that some adults who had undergone cancer treatment as children and young adults suffered from growing heart irregularities as they aged into their 30s and 40s.

"The take-home message is that long-term survivors of childhood cancer are a high-risk group for the development of premature symptomatic cardiovascular disease," said Dr. Steven Lipshultz, chairman of pediatrics at the University of Miami School of Medicine.

At issue are chemotherapy drugs known as anthracyclines. According to Lipshultz, the medications revolutionized childhood cancer treatment in the 1970s and helped contribute to today's high long-term survival rate -- almost 80 percent -- for kids with cancer.

But researchers have also found that survivors of childhood cancer, especially girls and black patients, become more likely to develop heart problems later on, Lipshultz said. Radiation treatment that encompasses the heart can also raise the risk of future disease.

Studies have suggested that the risk of heart disease in some long-term cancer survivors is eight times higher than in people who didn't have cancer or cancer treatment, Lipshultz said.

The Dutch researchers tracked 22 patients, averaging 39 years of age, who underwent chemotherapy as children or young adults. While the number of people was small, the study is believed to be the longest-lasting of its kind since the patients were followed for an average of 22 years.

Reporting in the July 20 online issue of the Annals of Oncology, the researchers found that 27 percent of the patients had systolic dysfunction, a condition where the heart's left chambers fail to pump effectively. And nearly half (45 percent) had diastolic dysfunction, where the left chambers of the heart aren't fully relaxed after pumping.

Both percentages rose significantly from a previous study of the patients in 1997, the researchers note. At that time, just 9 percent and 18 percent of the group had systolic and diastolic dysfunction, respectively.

It appears that the chemotherapy treatment somehow damaged cells in the muscles of the heart, said lead researcher Dr. Inge Brouwer, a pediatric oncologist with the University of Groningen in the Netherlands.

"We think that this damage to heart cells is ongoing after cessation of anthracycline treatment, but the exact mechanism that might cause these problems is not yet known," the researcher said.

What to do? Anthracyclines are considered effective in fighting childhood cancers, so doctors are now looking ways to prevent future heart disease.

According to the study, some patients are now receiving lower doses of chemotherapy drugs than in the past, and drugs to protect the heart are now available.

Former patients can also take action themselves. "Healthy lifestyle seems to be important in prevention of cardiac problems, so former patients need to be stimulated to stop smoking, take their exercise and reduce weight if necessary," Brouwer said. Treatment for high cholesterol or blood pressure may also be necessary, she said, and doctors should keep an eye out for not-so-obvious signs of potential heart problems.

More information

Find out more at the Candlelighters' Childhood Cancer Foundation.