Last week, it was cholesterol. This week, the focus is on fat as a new study calls into question guidelines suggesting that Americans should limit fat as part of a healthy diet.

A recently released study has concluded that the dietary advice given to Americans regarding fat intake is based on flimsy evidence, and may be plain wrong. According to researchers Zoe Harcombe of the University of the West of Scotland and James DiNicolantonio of the Saint Luke's Mid America Heart Institute, the dietary guidelines that suggest limiting fat consumption to 30 percent of total caloric intake and limiting saturated fat to around 10 percent are inconsistent with scientific evidence on the role of fat in the diet.

At the same time, an advisory panel that is chipping away at reshaping official dietary guidelines announced this week that it is lowering restrictions on fat and cholesterol and increasing restrictions on sugar intake, according to the New York Times.

To figure out where we went wrong on fat, we have to go back to the 1970s. That's when The Seven Counties Study was published, claiming that there was a correlation between dietary fat consumption and heart disease. But according to Harcombe and DiNicolantonio, that study was flawed. For starters, the original researchers included data from participants in seven countries who followed diets typical in those countries. But Harcombe and DiNicolantonio allege that the researchers had data from 22 countries, they just neglected to include the participants from countries where the diet was high in saturated fat but the incidence of heart disease was low.

The original study also ignored other important health factors that we now know affect heart health such as smoking rates, sugar consumption, and physical activity. What's more, Harcombe and DiNicolantonio suggest that the original guidelines were arbitrary. There was never any scientific evidence to suggest that limiting dietary fat consumption to 30 percent of total calories was any healthier than a diet that included a higher or lower percentage of fat.

“The bottom line is that there wasn’t evidence for those guidelines to be introduced,” Harcombe says. “One of the most important things that should have underpinned the guidelines is sound nutritional knowledge, and that was distinctly lacking.”

Despite these failings, the countries study prompted more than three decades of government warnings about dietary fat consumption. And those warnings have been heeded. According to the British Medical Journal, the percentage of calories from consumed fat has fallen from 40 percent to 30 since the 1970s. But in that same time period, obesity has doubled and heart disease remains the leading cause of death in the U.S.

So does that mean that hot dogs should be back on the menu? No, says Harcombe. While she admits that she does not know the magic number that Americans should shoot for when analyzing their diets, she suggests one rule that people can use to cut through the confusion. “It’s one message, in three words — eat real food,” she told Time magazine.

That includes an emphasis on plant foods and steering clear of processed foods — including processed meats or sugary foods — and stick to a diet based on whole foods, including meats, grains, vegetables and fruits. In fact, while you're at it, ditch the cigarettes and make sure you get a little exercise each day. That's a far better recipe for heart health than a diet based on arbitrary numbers. 

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