Rich foods, clotting, and heart attacks.

A high-fat diet may lead to an overly aggressive blood-clotting system, which in turn can lead to a heart attack in people with coronary artery disease.

Fat-laden diets tend to raise concentrations of cholesterol in the blood. Cholesterol is a fatty substance that builds up on the inner wall of the artery and along with other debris hardens into a substance called plaque. ff that plaque gets too thick, it can obscure the blood flowing through the heart's coronary arteries and thus cause a heart attack.

However, there's another way for a heart attack to occur: If a hunk of plaque breaks away from the artery wall, the body's clotting system attempts to repair the breach. In arteries already narrowed with plaque, the resulting blood clot can block the vessel, leading to a heart attack. People with a penchant for fatty foods may be at increased risk for a heart attack because their clotting system overreacts to such an injury and builds a monster clot, says George 3. Miller of the Medical College of St. Bartholemew's Hospital in London.

In particular, Miller says, a high-fat diet leads to increased activity of a blood protein called factor VII. Miller likens factor VII to the spark that sets off an explosion. His research suggests that people with a fat-filled diet are likely to have more active factor VII than people who eat low-fat foods.

For hours after eating a fat-rich meal, people have high concentrations of fat circulating in their bloodstream, Miller says. Somehow, that fat activates a blood factor that in turn ignites factor VII. Miller believes this scenario explains the observation that heart attacks surge in the predawn and early morning hours. The industrialized world's habit of eating on the run during the day means that most people don't sit down for a large meal until evening. People who eat a high-fat dinner may face an explosive situation when the alarm goes off in the morning, he says.