Wouldn't it be nice - a pill that would allow people to eat what they wanted, as much as they wanted, and not gain weight?
With an epidemic of obesity sweeping industrialized countries like Britain and the United States - and starting to affect other affluent places such as Japan and Hong Kong - drug firms are thinking along the same lines.But although the pharmaceutical industry has poured billions of dollars into obesity drug research, the outlook is not good for a magic bullet for the overweight any time soon.
"We need more potent and newer and better anti-obesity drugs," Dr. Nick Finer, an endocrinologist at Luton and Dunstable Hospital, told a recent conference.
The reasons why obesity drugs are needed are clear. Obese people have higher rates of heart disease and diabetes and cost health care systems millions of dollars. One-third of all Americans are overweight, and a quarter clinically obese - defined as being 20 percent above ideal weight or having a body mass index (weight in kg divided by height in meters squared) of above 30.
Researchers are looking at close to a dozen different approaches to formulating new drugs. The old amphetamine-based drugs have been largely discredited as useless and harmful.
New drug goals fall into three broad areas - curbing appetite, reducing the body's ability to absorb calories and raising the metabolic rate so that what does get eaten is burned off.
The two great hopes of recent months are dexfenfluramine, licensed by Interneuron Pharmaceuticals Inc. and sold under the brand name Redux, and Roche Products Ltd.'s orlistat, now being considered for U.S. and European licenses.
Redux works on serotonin, a neurotransmitter or message-carrying chemical that affects mood. Redux seems to help reduce appetite - but scientists admit they do not yet understand the exact mechanism.
Consumers were evidently desperate for such a drug - more than a million prescriptions were written for it in the first three months after U.S. approval last year.
Orlistat (Xenical) takes a different route. By limiting how much fat the body absorbs, it cuts calories and theoretically should help dieters keep weight off.
Five thousand patients put on a "modest" fat-reduced diet lost on average 8.5 percent of their body weight over a year. Those given a placebo but put on the diet lost an average of 5.4 percent.
Experts agree that the effects of drugs developed so far are modest - and do not last for long.
"All drugs show the same profile," said Gareth Williams, an expert in diabetes at the University of Liverpool. "First weight drops by eight to 10 kg (18 to 22 lb), then after six months it slowly drifts back up."
Scientists seeking an answer are looking to molecular biology to find more and more specific targets.
Dr. Jon Arch, an expert in vascular biology at SmithKline Beecham, said his company's efforts targeting one tiny part of brain cells known as the beta-3 adenoreceptor were disappointing so far.
"These drugs are remarkably effective in rodents but not in man," he said. "Either they just don't get absorbed or they get metabolized by the liver or they get kicked out by the kidneys."
Another possible target is uncoupling protein (UCP), which plays a vital role in metabolism by helping convert fat into body heat. Mice genetically engineered to lack UCP do not become obese, even when fed a high-fat diet.
Researchers are also finding out more about the possible genetic causes of obesity, having identified the ob (obesity) gene and the gene for leptin, which is secreted from fat cells and helps communicate with the brain as it regulates feeding behavior, metabolism and energy levels.
Then there is neuropeptide Y. "It is probably one of the key brain chemicals that regulates energy intake and expenditure in rodents," Williams said. "It has been found to induce obesity when given experimentally to rodents. But we can't do that in humans, so we don't know whether it does it in them."
Despite the careful focus of many of the drugs, it is becoming increasingly clear that a variety of causes - genetic, behavioral and biochemical - unite to cause obesity.
Nevertheless, and despite all the research into drugs, it is agreed that careful eating is the most effective way to lose weight.
Humans evolved through ice ages, droughts and other times of uncertain food supply. Those who could lay down a good supply of blubber in good times would be more likely to survive lean times - and pass on their genes.
It could take a long time to find a drug that could counteract the effects of hundreds of thousands of years of evolution.