Fat was once the devil. Now more nutritionists are pointing accusingly at sugar and refined grains.

Most people can count calories. Many have a clue about where fat lurks in their diets. However, fewer give carbohydrates much thought, or know why they should. But a growing number of top nutritional scientists blame excessive carbohydrates — not fat — for America's ills. They say cutting carbohydrates is the key to reversing obesity, heart disease, Type 2 diabetes and hypertension.

"Carbohydrates are a metabolic bully," Phinney says. "They cut in front of fat as a fuel source and insist on being burned first. What isn't burned gets stored as fat, and doesn't come out of storage as long as carbs are available. And in the average American diet, they always are."

Here's how Phinney explains it: When you cut carbs, your body first uses available glycogen as fuel. When that's gone, the body turns to fat and the pancreas gets a break. Blood sugar stabilizes, insulin levels drop, fat burns. That's why the diet works for diabetics and for weight loss.

When the body switches to burning fat instead of glycogen, it goes into a process called nutritional ketosis. If a person eats 50 or fewer grams of carbs, his body will go there, Phinney says. (Nutritional ketosis isn't to be confused with ketoacidosis, a dangerous condition that can occur in diabetics.)

Beyond the fat-burning effects of ketosis, people lose weight on low-carb diets because fat and protein increase satisfaction and reduce appetite. On the flip side, simple carbs cause an insulin surge, which triggers a blood sugar drop, which makes you hungry again.

"At my obesity clinic, my default diet for treating obesity, Type 2 diabetes and metabolic syndrome is a low-carb diet," says Dr. Eric Westman, director of the Lifestyle Medicine Clinic at Duke University Medical Center, and co-author of the new Atkins book. "If you take carbohydrates away, all these things get better."

http://articles.latimes.com/2010/dec/20/health/la-he-carbs-20101220