Are carbs worse than fat?

Love eating fatty french fries? Then you've certainly heard warnings that they're no good for you.

Consuming too much fat causes cardiovascular disease and diabetes, experts say, especially when they include saturated fatty acids, like those in deep-frying fats.

However, Jeff Volek, a professor of human sciences at the Ohio State University in Columbus, disagrees.

"There is widespread misunderstanding about saturated fat," he said. "In population studies, there's clearly no association of dietary saturated fat and heart disease."

His controlled diet study was supported by the Dairy Research Institute, the National Cattlemen's Beef Association and the Egg Nutrition Center and published in the open-access peer-review science journal "Plos One" on Friday (21.11.2014).

Its conclusion: saturated fat is not as bad as its reputation.

Carbohydrates, Volek argues, are the true evil.

High carbs, high fats

In the study, participants ate diets that progressively increased in carbohydrates while simultaneously reducing fat and saturated fat. Holding steady were the calories and protein.

As a result, all 16 participants suffered from a metabolic syndrome which placed them at a high risk of cardiovascular disease.

Meanwhile, doubling or even nearly tripling saturated fat in the diet had no effect on the total level of saturated fat in the blood, the researchers say.

For the carbohydrate eaters, however, the result was a higher level of a fatty acid called palmitoleic acid in blood samples. This acid is linked to an elevated risk for diabetes and heart disease, according to the researchers.

According to Volek, this finding "challenges the conventional wisdom that has demonized saturated fat."

'So what?'

Dieticians, however, say the finding is not surprising at all.

"It has been known for many years that increased carbohydrate intake stimulates the synthesis of fat in the liver," says Matthias Schulze of the German Institute of Human Nutrition in Potsdam. He adds that triglyceride levels, which transport fatty acids in the blood, rise under these circumstances.

"The fatty acid palmitoleic acid [which the researchers found in the carb-eaters' blood] is a marker of that."

Peter Stehle, a nutrition physiologist at University Bonn, agrees. A study with 16 participants, he says, doesn't change anything.

A perfect diet?

In the study, the carb-eaters' diets contained no more than 2500 calories per day. The diets started with 47 grams of carbs and 84 grams of saturated fat and ended with 346 grams of carbohydrates per day and 32 grams of fat.

Participants lost on average almost 22 pounds by the end of the trial.

Nutrition specialist Stehle points out that 47 grams of carbohydrates - which Volke and his team claims to be a healthy option - is too little, though.

"These participants must have had a deficiency of glucose," he says.

The body needs glucose for the brain, the muscles and many other organs to operate.

Uwe Wenzel, a professor of molecular nutrition research at University Giessen, adds that a diet with too few carbohydrates will make you lose weight but will also stimulate your body to produce ketone bodies out of fat. Those are water-soluble molecules that lower the pH of the blood, "and that is no good."

Wenzel assumes the effects measured in the study are due to the participants being overweight in the beginning and losing weight during the trial - that "the participants were getting more sensitive to insulin due to their weight loss."

According to Wenzel, the effects had nothing to do with saturated fats directly.

Take-home message

In the end, the experts agree that Volek's study will not change any dietary recommendations.

Too much fat in combination with carbohydrates will in the end make you gain weight, Wenzel says. Too much fat without any carbohydrates, though, will blanch your body and make it accumulate acid.

"Neither are a healthy option."

"The most important thing," Wenzel says, "is to have a healthy body weight - and not to be overweight."