The researchers from the Harvard School of Public Health say neither is more likely to either cause heart disease, or prevent it.

Atkin's and other low-carb diets have long claimed to prevent obesity and heart disease, but nutrition experts have always questioned the safety of encouraging people to eat animal proteins that are high in saturated fats and cholesterol.

Low-carb diets encourage people to eat more proteins and are popular for weight loss.

The researchers found in fact that the rate of heart disease among women who follow a low carbohydrate diet is no higher than it is among women who eat foods that are low in fat and high in carbohydrates.

For the study the team analyzed data collected over 20 years from more than 82,000 women participating in the Nurses' Health Study.

Researcher Thomas Halton says this does not mean that the two diets are equally good, in fact, they're both equally bad, but he says the study is an eye-opener and goes against a lot of what people think is common wisdom for nutrition.

The researchers say that the only diet that reduces the risk of the disease, and does so dramatically, is one where the fat and protein come from vegetable sources.

Women who showed a 30 percent reduction in the risk of heart disease over 20 years, tended to get their protein from beans, legumes, oatmeal, whole grain, tofu and brown rice, and their fat from nuts, olive oil and canola oil.

Halton says the reason that vegetable sources of protein and fat are so beneficial is that such foods produce a gradual increase in the blood sugar, not the rapid spikes generated by low-fat foods that are high in sugar.

The study is published in the current edition of the New England Journal of Medicine.

A 23-Year Survival Analysis of Prediagnostic BMI and Risk of Lethal Prostate Cancer

A team of Harvard scientists has peered into 23 years of health data on more than 22,000 physicians and concluded that men who are overweight or obese years before being diagnosed with prostate cancer are more likely to die of the disease than those who are of normal weight.

While no studies have definitively shown that obesity and/or higher Body Mass Index, or BMI, which measures body fat, increases the risk of developing prostate cancer, these studies showed that obese men at the time of diagnosis were more likely to have a cancer recurrence.

But according to Jing Ma, M.D., Ph.D., a researcher at the Brigham and Women's Hospital-based Channing Laboratory and associate professor of medicine at Harvard Medical School, few studies have focused on obesity and the risk of dying from prostate cancer.

In fact, she said, there is "considerable debate in the urology and cancer fields regarding whether rising PSA (Prostate Specific Antigen) is a good indicator for whether people will eventually die from prostate cancer or not."

Ma and her co-workers at Brigham and Women's Hospital and at the Harvard School of Public Health examined 23 years of data from the Physician's Health Study, which began in 1982 as a randomized, double-blind trial of aspirin and beta-carotene. More than 22,000 U.S. male physicians were recruited for the trial to study the role of aspirin and beta-carotene in preventing heart disease and cancer.

About 15,000 men provided blood samples at enrollment, along with information on their body weight and height, and their BMI was calculated. Approximately 99 percent of the original participants were tracked through questionnaires for 23 years, including cause of death.

By the end of 2005, 2,367 men had developed prostate cancer, while 265 died of the disease. They found that 39 percent of the participants were overweight and 3.4 percent were obese at the beginning of the study, and that higher BMI was positively associated with the risk of dying from prostate cancer. They also showed that the risk of dying from prostate cancer increased 8 percent for each point increase in BMI.

A person with a BMI of between 25 and 29.9 is considered overweight, whereas someone with a BMI of 30-plus is called obese. The physicians were in relatively good shape compared to the U.S. population in general. U.S. males between 50 and 69 are approximately 40 percent overweight and more than 30 percent are obese.

"It was surprising since it is a moderate association and the BMI was measured in 1982 and was on average eight to 10 years before developing prostate cancer," Ma said. "The beauty of the study is that we could factor out smoking at baseline, and tumor grade and stage didn't affect the trend."

"Some people might think that what they do today has little to do with cancer risk, especially for prostate cancer," Ma said, "and some individuals probably wouldn't believe that obesity has anything to do with prostate cancer. But we have found that if a man develops prostate cancer, being obese could put him at a higher risk of dying from the cancer. There is something many men can do about that."

She and her co-workers are exploring the underlying mechanisms that link being overweight and/or obese to prostate cancer progression. A better understanding of the risk factors that influence the disease's progression, said Ma, is imperative.

Prostate cancer is the most common type of cancer found in American men, other than skin cancer, and the third leading cause of cancer death in men. The American Cancer Society estimates that there will be about 234,460 new cases of prostate cancer in the United States in 2006, with approximately 27,350 deaths from the disease.

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