Food laden with saturated fat does not drive up levels of the "junk" nutrient in the blood, contrary to popular opinion, research suggests.
Higher consumption of carbohydrates, not saturated fat, was associated with changes linked to diabetes and heart disease, scientists found.
The discovery turns on its head the view of the harmful effects of eating too much saturated fat.
Butter, cheese, fatty cuts of meat, processed meat products such as sausages and bacon, cakes and biscuits are all examples of "unhealthy" foods high in saturated fat.
Starchy carbohydrates such as potatoes, bread, cereals, rice and pasta are considered important for health and should make up about a third of the diet, according to expert advice.
Professor Jeff Volek, from Ohio State University, said: "There is a widespread misunderstanding about saturated fat.
"In population studies, there is clearly no association of dietary saturated fat and heart disease, yet dietary guidelines continue to advocate restriction of saturated fat.
"That's not scientific and not smart. But studies measuring saturated fat in the blood and risk for heart disease show there is an association.