WE HAVE LONG BEEN TOLD THAT FEWER CALORIES AND MORE EXERCISE LEADS TO WEIGHT LOSS. And we want to believe that science is purely a matter of data-that superior research will always yield the right answer. But sometimes research is no match for a strong personality. No one better embodies that than Dr. Ancel Keys, the imperious physiologist who laid the groundwork for the fight against fat. Keys first made his name during World War II, when he was asked by the U.S. Army to develop what would become known as the K ration, the imperishable food supplies carried by troops into the field. It was in the following years that the fear 0f heart disease exploded in the U.S., driven home by President Dwight Eisenhower’s heart attack in 1955. That year, nearly half of all deaths in the U.S. were due to heart disease, and many of the victims were seemingly healthy men struck down suddenly by a heart attack. “There was an enormous fear overtaking the country,” says Nina Teicholz, author of the new book The Big Fat Surprise.”The heart-disease epidemic seemed to be emerging out of nowhere.”
Keys had an explanation. He posited that high levels of cholesterol-a waxy, fatlike substance present in some foods as well as naturally occurring in the body-would clog arteries, leading to heart disease. He had a solution as well. Since fat intake raised LDL cholesterol,(Bad cholesterol) he reasoned that reducing fat in the diet could reduce the risk of heart attacks. In the late 1950’s and 60’s Keys sought to flesh out that hypothesis, traveling around the world to gather data about diet and cardiovascular disease. His landmark Seven Countries Study found that people who ate a diet low in saturated fat had lower levels of heart disease. The Western diet, heavy on meat and dairy, correlated with high rates of heart disease. That study helped land Keys in 1961 on the cover of Time magazine, in which he admonished Americans to reduce the fat calories in their diet by a third if they wanted to avoid heart disease. That same year, following Keys strong urging, the American Heart Association (AHA) advised Americans for the first time to cut down saturated fat. “People should know the facts,” Keys told Time magazine. “Then if they want to eat themselves to death, let them.”
Keys work became the foundation for a body of science implicating fat as a major risk factor for heart disease. The Seven Countries Study has been referenced close to 1 million times. The vilification of fat also fit into emerging ideas about weight control, which focused on calories in vs. calories out.”Everyone assumed it was all about the calories,” says Lustig. And since fat contains more calories per gram (9 per gram) than protein (4 per gram) or carbohydrates, (4 per gram) the thinking was that if we removed fat, the calories would follow.
That’s what Keys, who died in 2004, believed, and now it’s what most of us believe to. But Keys research had problems from the start. He cherry picked his data, leaving out countries like France and West Germany that had high fat diets but low rates of heart disease. Keys high lighted the Greek island of Crete, where almost no cheese or meat was eaten and people lived to an old age with clear arteries. But Keys visited Crete in the years following World War II, when the island was still recovering from German occupation and the diet was artificially lean. Even more confusing, Greeks on the neighboring isle of Corfu ate far less saturated fat than Cretans yet had higher rates of heart disease.”It was highly flawed,” says Dr. Pieter Attia, the president and director of the Nutrition Science Initiative, an independent obesity research center. “It was not on the level of epidemiology work today.”
Keys unshakable confidence and his willingness to take down any researcher who disagreed with him was at least as important as his massive data sets. Keys research also played into a prevailing narrative that Americans had once eaten a largely plant based diet before shifting in the 20th century to meals rich in red meat. Heart disease followed, as if we were being punished for our dietary sins.
The reality is that hard numbers about the American diet are scant before mid century and all but nonexistent before 1900. Historical records suggest Americans were always voracious omnivores, feasting on the plentiful wild game available throughout the country. (That is the same for us in South Africa) In his book Putting Meat on the Table, the historian Roger Horowitz concludes that the average American in the 19th century ate 68 to 91 kg of meat per year in line with what why eat now.
But the anti fat message went main stream, and by the 1980s it was so embedded in modern medicine and nutrition that it became nearly impossible to challenge the consensus. Dr. Walter Willett, now the head of the department of nutrition at the Harvard School of Public Health , tells that in the mid 1990s, he was sitting on a piece of contrary evidence that none of the leading American science journals would publish. “There was a strong belief that saturated fat was the cause of heart disease, and there was resistance to anything that questioned it, Willett says. “He had been running a long term epidemiological study that followed the diets and heart health of more than 40000 middle aged men. Willett found that if his subjects replaced foods high in saturated fat with carbohydrates, they experienced no reduction in heart disease. Willett eventually published his research in the British Medical Journal in 1996.
In part because of Willett’s work, the conversation around fat began to change. Monounsaturated and polyunsaturated fats the kind found in some vegetables and fish were found beneficial to heart health. The Mediterranean diet, rich in fish, nuts, vegetables and olive oil, surged in popularity. And the Mediterranean diet isn’t low in fat, not at all. Up to 40% of its calories come from poly and monounsaturated fat. Today, medical groups like the Mayo Clinic embrace this diet for patients worried about heart health, and even the fat phobic AHA has become receptive to it. There is growing evidence that the Mediterranean diet is a pretty healthy way to eat, say’s Dr. Rose Marie Robertson, the chief science officer of the AHA.
But what about saturated fat? Here, the popular wisdom has been harder to change. The 2010 USDA dietary guidelines recommend that Americans get less than 10% of their daily calories from saturated fat. The AHA is even stricter: Americans over the age of 2 should limit saturated fat intake to less than 7% of calories, and the 70 million Americans who would benefit from lowering cholesterol should keep it under 6% of calories-equal to about two slices of cheddar per day. When you replace saturated fats with polyunsaturated and monounsaturated fats, you lower LDL (Bad cholesterol) says Dr. Robert Eckel, a past president of the AHA. But that’s not the full picture. The more we learn about fat, the more complex its effects on the body appear.