The Origin of The Low-Fat Diet

The history of the low-fat diet recommendations is rich with interesting characters, powerful institutions and twisted studies.

A funding explosion

In the 1940s, the American Heart Association (AHA) went from a small unfunded group, to an extremely well funded one, when Procter and Gamble (P&G) awarded them a million dollar prize, the equivalent of $17 million today. Just 20 years later, the AHA was the largest non-profit in the USA, with over 300 chapters bringing in over 30 million dollars annually. The AHA was focused on diet as the primary cause of heart disease. They were empowered by their founder Dr White’s apparent success treating President Eisenhower after his heart attack, which led to a 40% increase in their income in 1 year. At the time, the AHA was still cautious with dietary recommendations, stating that it was too soon to claim that high cholesterol predicted heart attacks. They simply recommended limiting fat as a method of weight loss, and did not support Ancel Keys’ “rigid” stance on dietary intakes.

Control the institutions

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In the 1960s, Keys and his supporter Dr Jeremiah Stamler took control of the American Heart Association (AHA) and the National Institute of Health (NIH), and gained a front cover story in Time magazine. Neither Keys or Stamler had training in epidemiology, nutrition science or cardiology, but they still managed to convince their peers that the ‘diet-heat hypothesis’ was accurate. This changed the AHA’s stance on diet, stating that cutting saturated fat and cholesterol from the diet would reduce risk of heart attacks, and recommended replacing these fats with seed oils instead. These were the first national nutrition guidelines ever created, and since then, the AHA has become the global leader in nutrition advice.

Advice for thee, not for me

In the Time magazine article, Keys recommended cutting dietary fat from 40% to 15% of total calories, saturated fat from 17% to 4%, insisting this was the only was to prevent heart disease. “People should know the facts. Then if they want to eat themselves to death, let them” Keys said.

Despite all of this, Keys did not follow his own advice, eating scrambled eggs and bacon for breakfast, and dinners of steak, chops and roast. When questioned he replied “no-one wants to live on mush”. The media keenly showcased the theory, using Keys talent for publicity, fiery language, and seemingly definitive solution, which was more compelling than the cautious approach of other physicians.

So simple, it’s wrong

Blocked coronary artery. Computer artwork of a clot (red) in a coronary artery. The clot has been caused by atherosclerosis, the build up of fatty plaques (yellow) on the artery wall.

Paired with the advice from the now high-status AHA, the public believed that the dietary cause of heart disease was fact. The chain of causation seemed to make intuitive sense; saturated fat increases cholesterol, cholesterol blocks arteries, narrow arteries cause heart attacks. Each of these statements have since been disproven, and amazingly the data to disprove the theory already existed. Yet no matter how many studies were published to the contrary, Keys and his colleagues would not acknowledge the results as accurate.

Blind to the truth

The explanation for this poor scientific rigour is selection bias. Keys felt that the burden of proof was on other to disprove him, and that his own theory did not require skepticism. Keys could not imagine that there could be any negative effects caused by reducing dietary fat. Researcher Pete Ahrens was not convinced, and stated that the ‘diet-heart hypothesis’ did not yet have sufficient evidence to be considered fact.

Ahrens suggested that carbohydrates could be causing obesity and disease, and predicted that a low-fat diet would increase consumption of these high-carbohydrate foods. Ahrens was interested in triglycerides (a type of fat circulating in the blood), not serum cholesterol, as a health marker. He discovered that those with heart disease had high triglycerides far more often than high serum cholesterol, and observed that triglycerides spiked following consumption of carbohydrates. At lectures he would show two test tubes of blood; one containing clear serum, the other cloudy with fat. He shocked attendees when he announced that the cloudy blood came from someone a high-carbohydrate diet, and the clear blood from someone eating high fat. Ahrens findings would suggest that a healthy diet was the opposite to that which Keys proposed. Despite being one of most respected scientists in the field, he was unable to overcome the powerful position enjoyed by Keys.

Bullying wins

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Keys and Stamler aggressively disparaged their opponents, and mocked Ahrens for his slow, methodical approach, as they saw themselves as responding with appropriate urgency. Stamler was proud of “shooting down” Yudkin’s sugar theory, and called prominent cardiologist and critic Michael Oliver “a scoundrel”. Keys was equally scathing in response to the rigorous and thorough analysis of his work presented by Texas A&M professor Raymond Reiser, describing it as ‘distorted as a fun-house mirror’, and claiming that Reiser ‘obviously has no comprehension’. Reiser responded, clarifying that it was not his intention to smear reputations with the analysis. However, these kinds of reputation-damaging responses slowly silenced opponents of Keys theory.

Write it off as nonsense

The study of the Masai by George Mann was still clearly undermining the ‘diet-heart hypothesis’, so several universities sent research teams to Kenya to find flaws in the study. They instead found exactly what Mann had, but postulated that the reason for the Masai’s health was genetic. This theory was quickly disproven by the fact that Masai who moved to urban areas had elevated cholesterol. Keys of course claimed that data about “the primitive nomads has no relevance”, believing his international populations were better reference points. Stefansson (who had studied and ate like the Inuit), thought he would be heralded for his research, but was completely wrong. Keys publicly dismissed Stefansson’s work as “exotic and irrelevant”, describing that ‘although their bizarre manner of life excites the imagination, especially that popular picture of the Eskimo happily gorging on blubber, on no grounds was it possible to suggest that the case of the Inuit contributes anything, and it certainly does not demonstrate an exception to the diet-heart hypothesis’.

Cholesterol fails to predict disease

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George Mann was a successful researcher prior to studying the Masai. He was the associate director of one of the most famous heart disease studies ever undertaken, The Framingham Study. Starting in 1948, five thousand middle-aged men and women participated, with comprehensive physicals, detailed interviews and tests every two years. The study sought to investigate factors such as smoking, high blood pressure and genetics played a part in the development of heart disease. After six years of study, they announced that high total cholesterol predicted heart disease. This finally gave researchers a welcome indicator to measure prior to the death of their patients, and validation of the diet-heart hypothesis. It was presumed therefore, that any food that raised cholesterol would lead to a heart attack. However, 30 years later, the Framingham follow-up study showed that this original correlation was weakened. It was found that half of the people who had heart attacks had cholesterol below the normal level of 220mg/dL, and men aged 48–57 with mid-range cholesterol 183–222mg/dL had greater heart disease risk than those with higher cholesterol (222–261mg/dL). Total cholesterol was clearly not a reliable predictor of heart disease after all.

Just exclude the results

As these follow-up figures contradicted the message they had been confidently proclaiming for 30 years, the results were published far more quietly than the originals had been. Instead, the researchers shifted the conversation to types of cholesterol, HDL and LDL, although these too turned out be disappointing in their predictive power. The study also failed to demonstrate that lowering cholesterol reduced risk, finding that for each 1% mg per dL drop in cholesterol, there was an 11% increase in coronary and total mortality. As shocking as this outcome was, it is never included in the Framingham study reviews, despite other research finding similarly.

Bury them in the basement

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George Mann also worked with a nutritionist to analyse food samples of 1000 subjects, and showed that saturated fat consumption was not related to heart disease, concluding “no relationship found”. It “went over like a wet blanket with my superiors at NIH” said Mann. As a result, the NIH would not allow Mann to publish those findings, instead relegating them to storage in the NIH basement. Only decades later were they quietly published, buried deep in 28 volumes of journals. It wasn’t until 1992 that a Framingham study director acknowledged these findings in an obscure editorial, stating that “the more saturated fat one ate, the lower the person’s serum cholesterol, and they weighed the least”.

Agree or die

George Mann’s findings opposed Keys, and thus devastated his career. He lost the ability to publish research in any prominent scientific journals, and had his research grants cancelled. How did Keys have such power? “You have to understand what a forceful and persuasive person Keys was. He could talk to you for an hour, and you would utterly believe everything he said”, Mann explained. Yet, it wasn’t just Keys’ power and bullying that managed to silence a generation of intelligent scientists and researchers. It was through enshrining the theory in institutions, such as the AHA and NIH. If any new scientists wanted to conduct research, they had to agree with the diet-heart hypothesis in order to receive funding grants from these two institutions.

Stronger together

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In 1948 the NHI lobbied the government to setup the National Heart Institute (NHI), which became the National Heart, Blood and Lung Institute (NHLBI) which still exists today. The AHA and NHLBI have always been closely related, jointly reporting their progress against heart disease, creating joint task forces, running joint conferences, and celebrating their 30th anniversaries together. The history of these institutions is the history of heart disease research, with everything opposing their position excluded from it. A small group of men from research institutes, teaching hospitals and medical schools formed expert panels that worked closely with the AHA and NHLBI. They had overlapping responsibilities, co-authored influential articles, sat on the boards of influential journals, peer reviewed each others work, and dominated the major professional conferences. Together, these institutes controlled (and continue to control) the vast majority of funds for cardiovascular research, a total of $1.5 billion by 1995.

Too big to fail

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The more money spent trying to confirm the diet-heart hypothesis, the harder it became to reverse their position. A large amount studies failed to confirm the theory, so the results had to minimised, rationalised, and distorted, because by now the diet-heart hypothesis was taken as fact. Still, other biochemical processes that could lead to heart disease were abandoned by researchers in favour of the cholesterol theory. George Mann described this as a history “more political than scientific”, controlled by “a heart mafia” who had “supported the dogma and hoarded research funds”.


This article was based on the incredible book ‘The Big Fat Surprise’ by Nina Teicholz. Her deeply researched book is filled with data and stories detailing the evolution of the ‘diet-heart hypothesis’, which is the basis for modern food guidelines and medical treatments. Please consider purchasing a copy from her website, a local book store, or Audible.

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