His waiting room ? only minutes from the beachfront walkways where roller-bladers whiz by in bikinis ? is full of gray-haired patients.

This 50-something cardiologist set about creating a regime to give a more successful dietary formula for his patients to avoid heart attack.

Now his book "The South Beach Diet" has sold three million copies, and translations are in the works.

Agatston believes the popularity of his and other diets shows the United States is waking up to a worrying increase in obesity, projected to affect 40 percent of the adult population by 2010, if current trends continue.

"The obesity trend is reversible," he told AFP.

"Just as the food industry responded to the low fat guidelines and our lifestyle, I'm hopeful that with the realisation of the role of the glycemic index, the food industry will be responding, it is already responding, creating healthier food, higher on fibres," he said.

His diet relies heavily on fibres, which aid digestion and absorb blood sugars.

"When you take the fibre out of the food, you get a very rapid rise in blood sugar, that causes a response ... and that's where you get horrible cravings and you're hungry," he said.

That "is the most important cause of the epidemic of obesity and diabetes," said the cardiologist, whose diet is endorsed by dieticians and physicians.

Agatston's plan doesn't require abandoning carbohydrates and boosting protein intake, like the popular Atkins diet, nor does it rule out all fat.

Instead, the diet aims to get the stomach to work harder and to flush out industrial foods, which tend to include extra sugar, like in hamburger buns.

"I did not plan to create a diet, the orientation was preventing heart disease," he said.

Diet plans that cut back on carbohydrates but include fats are bad for heart patients, he said.

Before recommending his diet to patients, Agatston tried it out himself and on his colleagues. All were delighted to see the weight drop off them.

"We were just amazed by the success. This was in 1995-96. People were so happy they were sending Xerox copies to relatives around the country," he said.

"It's simple, we are not counting fats or calories. It also makes clear that the good fats are not only neutral but are good for us," he said.

"Our goal was first to prevent heart attacks or stroke. You cannot do that for a couple of weeks, for a wedding or to fit in a bathing suit. It's a way of life. And you lose weight without being hungry or feeling restricted," he said.

"I'm back on the diet. It requires discipline, in planning, especially when travelling."