Those who are considering the claims that climate change is “settled science” would do well to review the history of the study of coronary heart disease.

Crossfit, the hip workout program, would seem to be a strange bedfellow for climate-change skeptics. The fitness brand is known for its intense workouts and cult-like following, not necessarily for its politics or public-policy positions. But Crossfit gurus have been tenacious and vociferous opponents of what they see as bad science as it relates to health and nutrition. Perhaps most notably, they have led the counterattack against what was once considered settled science — that cholesterol and fat are dietary enemy #1 and leading contributors to shorter life spans.

The idea that dietary fat was fatal gained legitimacy with help from the U.S. government. A few staff members from a George McGovern-led Senate committee “almost single-handedly changed nutritional policy in this country and initiated the process of turning the dietary fat hypothesis into dogma,” said Gary Taubes in Science back in 2001. The bureaucrats likely had great intentions, but they based their flawed guidance off a study that used cherry-picked data to “prove” the author’s hypothesis. The author, like the Committee staff, had good intentions, but he made some big jumps to get from correlation to causation. His analysis of coronary heart disease focused on the fat and ignored other factors like smoking, stress, activity levels, and obesity.

The Department of Agriculture translated the Committee’s dogma into policy: fat-free and reduced-fat products became the norm for any food program that involved government funding — school lunches, WIC, and SNAP — and received what was effectively free advertising in the form of USDA guidelines that strongly encouraged people to avoid fat and cholesterol. As is almost always the case when bureaucrats intervene, the Law of Unintended Consequences was in full effect. Consumers dutifully modified their eating habits, replacing the fat with large quantities of carbohydrates. Although the studies need to be taken with a grain of salt (if that wasn’t a no-no as well), recent research suggest a high-carb diet may be much more harmful than a high-fat diet. Thanks to the sugar and carbs (with an assist from more sedentary lifestyles), obesity rates have climbed steadily, from the mid-teens when the dietary fat bogeyman was first introduced to well over 30% today. Diabetes has followed a similar trend.
As a result of the bureaucratic meddling, millions of people are worse off and billions more dollars have been spent on healthcare (often for obesity-related illnesses) than had we maintained the status quo (fat isn’t dietary enemy #1).

One of the most vocal critics of the fat-is-bad fallacy framed it this way:

The history of the national conviction that dietary fat is deadly, and its evolution from hypothesis to dogma, is one in which politicians, bureaucrats, the media, and the public have played as large a role as the scientists and the science. It’s a story of what can happen when the demands of public (health) policy-and the demands of the public for simple advice run up against the confusing ambiguity of real science.

Another skeptic wrote:

For 50 years an increasingly specious, pseudoscientific dogma has been growing in the Western World. This hypothesis originally proposed that coronary artery disease … is caused by the kind and amount of fat in our diets. That hypothesis was based upon fragile and selected data. The hypothesis has now been tested in dozens of clinical trials costing hundreds of millions of dollars. In adequate trials, that answer has been the same: dietary treatments are not effective. The statements ring just as true if we replace fat and coronary heart artery disease with fossil fuels and climate change. Whether it purports to study biology or climate, agenda-driven research that merely seeks to validate politically popular ideas isn’t science. The question of dietary-fat-heart-disease correlation should also give us pause when we consider climatology. If we have this much trouble proving hypotheses when we have a relatively reliable sample population to collect data from (human beings), it would be foolhardy to believe that we can definitively assess something as complex as global climate trends, much less predict where those causes and effects will take us decades from now.