Robert C. Atkins, 72, the cardiologist and best-selling author who three decades ago declared war on sugar and flour with a popular low-carbohydrate, high-protein diet that was dismissed by the medical establishment as nutritional folly, died April 17 at a New York hospital. He slipped on an icy sidewalk nine days earlier while walking to work from his home in Manhattan, severely injuring his head.

He underwent surgery for a blood clot, but later went into a coma. He had been hospitalized for cardiac arrest last April, but he said it was related to an infection of the heart and was not related to the diet.

Dr. Atkins became a figure of national controversy in 1972 after advocating a diet that emphasizes meat, eggs and cheese and discourages bread, rice and fruit. His first book, "Dr. Atkins' Diet Revolution," began luring dieters away from the tyranny of hunger-inducing lettuce regimes and went on to become one of the 50 best-selling books ever.

On the Atkins diet, up to two-thirds of calories may come from fat -- more than double the amount recommended by most medical professionals. Carbohydrates have long been described by the U.S. government and nutritionists as the foundation of a good diet. Eating calorie-dense fat is what makes people fat, they say, and eating saturated fat is dangerous.

To Dr. Atkins, the key dietary villain in obesity was carbohydrates. He argued that they make susceptible people pump out too much insulin, which in turn encourages them to put on fat. Fat in foods can be a dieter's friend, Dr. Atkins said, in part because it quenches appetite and stops carbohydrate craving.

He also recommended that people following the diet take 20 vitamin and mineral pills a day. He himself took 60. The 6-foot-tall physician said he kept his weight at about 189 pounds, down from a high of 225.

The publication of Dr. Atkins' first book came when the saturated fat of meat and dairy products were being recognized increasingly as a nutritional evil, and low-fat, high-carbohydrate diets were gaining favor. In 1973, the American Medical Association officially declared the diet unhealthy, and Congress summoned him to Capitol Hill to defend the plan. The New York Board of Health later tried, unsuccessfully, to revoke his license.

Labeling the diet "potentially dangerous," the AMA said the diet's scientific underpinning was "naive" and "biochemically incorrect." It scolded the book's publishers for promoting "bizarre concepts of nutrition and dieting."

Despite this, Dr. Atkins' books sold 15 million copies, and millions of people tried the diet. His philosophy enjoyed a resurgence in the 1990s with "Dr. Atkins' New Diet Revolution," which sold more than 10 million copies worldwide and spent five years on The New York Times bestseller list.

His book "Atkins for Life" has topped best-seller lists since its release in January.

He was the host of "Your Health Choices," a nationally syndicated radio show, and published a monthly newsletter, "Dr. Atkins' Health Revelations." His company, Atkins Nutritionals, which sells diet foods and supplements, had more than $100 million in revenue last year.

Despite the diet's popularity, criticism persisted, with many detractors arguing that the diet could affect kidney function, raise cholesterol levels and deprive the dieter of important nutrients. Dr. Atkins said no study showed that people with normal kidney function developed problems because of a high-protein diet, and he never gave in to his detractors.

In 1981, when a rival diet guru, Nathan Pritikin, said the Atkins diet could cause everything from heart problems to bad breath, Dr. Atkins threatened him with $5 million libel and slander suit.

The American Heart Association issued a strong recommendation in 2001 against following high-protein diets, including the Atkins Diet, Protein Power, the Zone and Sugar Busters. The AHA said there might be short-term weight loss from temporary fluid loss, but said that health benefits were "not demonstrated over the long term."

This year, Dr. Atkins's diet approach was vindicated in part when a half-dozen medical studies were reported to show that people on the Atkins diet lost weight without compromising their health. The studies showed that Atkins dieters' cardiovascular risk factors and overall cholesterol profiles changed for the better.

Still, many of the researchers were reluctant to recommend the Atkins diet, saying a large study now underway could settle lingering questions about its long-term effects. The obesity epidemic that has overtaken Americans in recent decades has continued unabated. Americans are said to spend $35 billion a year on commercial weight-loss plans and products.

Dr. Atkins was born in Columbus, Ohio, and raised in Dayton, Ohio, on a diet he later said emphasized meat and potatoes for dinner and doughnuts for breakfast. He studied medicine at the University of Michigan and Cornell University.

He told interviewers that, after gaining 30 pounds during medical school, he tried unsuccessfully to lose weight. He first followed a controlled carbohydrate diet in 1963 after reading about it in the Journal of the American Medical Association. He said he lost 27 pounds in six weeks and soon converted his fledgling Manhattan cardiology practice into an obesity clinic.

An article about his low-carbohydrate "eat all you want" advice was published in Vogue in 1970, generating 1 million requests for copies of his diet plan, which lead to his first book, "Revolution."

In later years, Dr. Atkins founded the Foundation for the Advancement of Innovative Medicine, as well as the Robert C. Atkins Foundation, which finances diet research, sponsoring research at Duke University, the University of Connecticut and Harvard University.

Survivors include his wife of 15 years, Veronica Atkins of New York; and his mother, Norma Atkins of Palm Beach, Fla.

Robert C. Atkins's diet recently gained some medical validation.