The Low Fat Doctrine Part II: The Dissenters
In Part I of this series we explored how the Low Fat Doctrine (LFD) came to dominate our thinking on diet and health. By the end of the 20th Century the idea that a healthy diet restricted fat consumption was largely unquestioned in mainstream biomedicine and in the popular culture. One of the pillars of that mainstream, the American Heart Association, created a “Heart-Check” certification program which specifies that food items meet the following criteria:
- Total Fat: Less than 6.5 g
- Saturated Fat: 1 g or less and 15% or less calories from saturated fat
- Trans Fat: Less than 0.5 g
- Cholesterol: 20 mg or less
- Milk and milk alternatives must have 130 calories or less per 8 fl oz. [precludes whole milk]
But remarkably this consensus on what constitutes a healthy diet had been reached without the benefit of any valid scientific studies. The primary scientific rationale for the LFD was derived from what are called “observational studies.” These include the Seven Countries study and the Framingham study described in Part I. As the term indicates, in such studies the investigator simply observes (and records) events as they take place. In this case the observations included what people were eating and what was their state of health. And thus researchers observed that people who eat less fat (and related compounds) seemed to have less heart disease than those who ate more fat.
The problem is that observational studies can never establish a causal relationship between a risk factor and a disease. This principle is not under dispute and is the virtual foundation of all clinical science. The only way to reliably establish a causal relationship between diet and health is through experimental studies in which the researcher actually controls the behavior of the subject, in this case, his or her diet. By the late 1990s no such experimental study had ever been performed to test the validity of the LFD.
Not only was there an absence of valid experimental studies, but subsequent review of the observational studies which formed the basis of the LFD found them to be less than convincing. The finding that dietary fat and cholesterol was associated with heart disease was in fact inconsistent and conflicting, And when any association was found, it’s apparent effects were very small. Most concerning is that fact that the seminal data on which the LFD was based, the Seven Countries Study, was deeply flawed even by the low standards of observational studies. The investigators of the study appear to have chosen the countries in the study based on pre-existing data that they knew would support the fat/heart disease hypothesis. Had they chosen different countries (e.g., Switzerland, France, Germany, all of which consume high levels of dietary fat and have low rates of heart disease) the results would have been dramatically different.
The first notable dissenter from LFD orthodoxy was Robert Atkins, MD. Dr. Atkins was a cardiologist who, in order to loose weight himself, tried a diet that restricted carbohydrates and “starches.” It worked for him. In 1972 Atkins published his wildly popular diet book, “Dr. Atkins’ Diet Revolution,” and created a literal low-carb empire of publications, products and programs based on his low-carbohydrate diet.
While Atkins succeeded personally as an entrepreneur he was mostly treated as a pariah and charlatan by the medical mainstream and for decades he was the lone prominent LFD contrarian. But over these decades the scientific foundations of the LFD continued to erode and the ranks of the dissenters grew.
Interestingly, much of the most credible and reliable analysis of the LFD came, not from the biomedical research community, but from science journalists. In 2002, Gary Taubes of the wrote, “What if It’s All Been a Big Fat Lie,” for the New York Times Magazine. Taubes wrote a book-length “Good Calories, Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health.” More recently journalist Nina Teicholz wrote, “The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.”
The mainstream scientific community eventually caught up and we now have a reasonable set of experimental clinical studies on the effects of a low fat diet. These include long-term studies measuring rates of heart disease and related disorders and short-term studies looking at weight loss and metabolic indicators. In virtually all cases the low fat diet failed to demonstrate any benefits and in many cases was shown to be less healthy than other dietary approaches. And these findings have resulted in many in the medical establishment renouncing the low fat approach. The British Medical Journal recently observed:
“It is time to bust the myth of the role of saturated fat in heart disease and wind back the harms of dietary advice [a low fat, high carbohydrate diet] that has contributed to obesity.”
Ironically, because of its prominence in our culture and consequent scientific scrutiny, the only dietary approach to have been eliminated from consideration as an optimal diet is the standard low-fat, high carbohydrate diet.
So the Paleo diet wins, right? Well, no. Yes, it turns out that the low fat approach is not valid, but this fact does not indicate that any other approach is optimal. The question of what is the healthiest diet is very much an unanswered question. I will examine what we do and do not know about diet and health in subsequent posts.
Next week, Part III: Beyond the Low Fat Diet
Postscript: One day after last week’s Part I of this series was posted, Time Magazine featured a cover story titled, “Eat Butter. Scientists labeled fat the enemy: Why they were wrong.” Interesting. It is at the least an indication that even at the level of the popular media the LFD seems to be doomed. But a word of caution… Time Magazine is not (nor is any other popular media outlet) a reliable source for health news. Thirty years ago Time featured another cover story titled, “Cholesterol: And now the bad news…” Oops.