Is tribalism undermining objectivity about low-carb, high-fat diets?

Anyone who is active on social media has come to expect a certain degree of tribalism around the issues of the day: guns, climate change, abortion, politics, and the like. We’ve been surprised to see it creep into the online conversation about nutrition science, especially the discussion about low-carbohydrate, high-fat diets. Even more surprising to us is that such advocacy sometimes comes from health professionals, scientists, and journalists, from whom we would normally expect a certain degree of objectivity.

These diets aren’t new. William Banting described in 1863 how a low-carbohydrate diet helped him lose weight, and since the 1970s the low-carb Atkins and South Beach diet books have sold millions of copies. Emerging data show that low-carb, high-fat diets can lead to reduced weight and better control of blood sugar, insulin, triglycerides, and possibly blood pressure. But they may increase cholesterol in the bloodstream, which has been associated with an increased risk of heart disease. That doesn’t necessarily mean low-carb, high-fat diets increase the risk of heart attack in everyone — or even in those with high cholesterol — because of the many potential benefits associated with these diets.

It’s a classic issue of balancing benefits and risks, one complicated because it isn’t clear if, how much, or in whom an increase in cholesterol even matters. That’s why there is general consensus that rigorous clinical trials are needed to answer this critical question.

The role of advocates who work on behalf of a cause or group can be essential to the success of these movements. But advocates also inflame the bitterness inherent in these battles. Given the current discourse in nutrition science, it can be hard to disentangle science from advocacy.

The idea that a dietary intervention might affect heart attack risk isn’t complicated or controversial. According to the cholesterol hypothesis, too much low-density lipoprotein (the so-called bad cholesterol) in the blood leads to its deposition in artery walls; the resulting plaque can block arteries and lead to heart attack or stroke. This theory has been bolstered by decades of evidence ranging from epidemiological associations to genetic studies and interventional drug trials. There may be no better studied pathway in modern medicine.

We believe in low-carb, high fat nutrition. One of us (E.J.W.) advises a company that uses this approach to treat individuals with type 2 diabetes and also recently co-founded a company using this approach for weight loss. The other (N.G.) uses low-carb, high-fat nutrition with her own patients and is the principal investigator of multiple studies of low-carb, high-fat nutrition in type 1 and 2 diabetes. We see this approach to nutrition as an exciting tool in the management of weight and cardiometabolic disease.

Yet we are disturbed by the discourse surrounding these diets, which often feels less like science and more like cheerleading. To be sure, nutritional tribalism is not limited to discussions about the relative merits or demerits of low-carb, high-fat diets. The evidence that nutrition has become a team sport is found in Twitter handles of individuals rooting for their favorite nutritional movement, such as small plant emojis in the Twitter handles of vegan advocates or a Ó in those promoting carnivore-type diets.

To bolster their cause for low-carb, high-fats diets, these advocates, including some scientists and doctors, claim that the cholesterol hypothesis is a conspiracy led by pharmaceutical companies in an effort to sell more drugs. Others have suggested that cholesterol may actually protect against cardiovascular disease. This goes on and on.

The effort to discredit the role of cholesterol in cardiovascular disease is striking because the evidence linking elevated cholesterol to heart attack risk is so strong. This makes us wonder why advocates might take this approach.

It’s possible that acknowledging an unknown risk might undermine or discredit the benefits of low-carb, high-fat nutrition. But that kind of thinking ignores a central tenet of medicine: Everything we do in medicine — from appendectomies to cancer chemotherapies to diet therapy — has benefits and risks. If a chemotherapy has a 10% chance of a side effect, that doesn’t make it any less likely to cure the cancer. So why would we treat the science of nutrition any differently? Perhaps because science has morphed into advocacy. Successful advocacy demands a clear narrative, yet science and biology are inherently gray.

The conversation about low-carb, high-fat nutrition is being painted as binary without room for nuance, when nuance is exactly what is required. The choice for individuals following low-carb, high-fat diets isn’t should they quit the diet or ignore the science. There are other choices, such as seeking testing to better define cardiovascular risk or taking a statin or other medication if needed. It’s also possible to change the types of high-fat foods in the diet, emphasizing those with unsaturated fats such as olive oil, salmon, avocado, or nuts while eating fewer foods with saturated fats such as butter, cream, and bacon. These approaches aren’t anti-low-carb, high-fat nutrition.

Nutrition science may be especially ripe for advocacy because of the linked epidemics of obesity and type 2 diabetes that so clearly stem from our changing lifestyles. And everyone has a stake in nutrition. But that is all the more reason we should be clear-eyed about what we know, even if what we know is “we don’t know.” We all have to eat, and make our choices based on imperfect evidence.

Of course, if a high-quality, large-scale, randomized control trial showed conclusively that the risks of the low-carb, high-fat approach outweighed the benefit, as health professionals and scientists we would accept that. In the other direction, if low-carb, high-fat diets were shown to protect against cardiovascular disease — regardless of their effect on LDL cholesterol — then that should be accepted and integrated into clinical practice.

We believe that the intrusion of advocacy into science has led to reductionism and the creation of false dichotomies. We believe that scientists, health care professionals, and journalists must avoid intentionally confusing or alarming the public in an attempt to discredit legitimate science, ultimately in the name of advocating for an agenda.

In addition to being dangerous, such ostensible advocacy appears to be an intentional attempt to degrade the public’s trust in science. One need look no further than the tragedy of the false story linking vaccines to autism as an example of what can and will result.

Nicola Guess, Ph.D., is a registered dietitian, associate professor of nutrition at the University of Westminster in London, head of nutrition at the Dasman Diabetes Institute in Kuwait, and a director of CityDietitians, a private clinical and consultancy company based on London. Ethan J. Weiss, M.D., is a preventive cardiologist and associate professor of medicine at the University of California, San Francisco.

Guess reports having received research or fellowship funding from Diabetes UK, the Medical Research Council, Diabetes Research and Wellness Foundation, American Overseas Dietetic Association, Chronic Disease Research Foundation, Winston Churchill Memorial Trust, and Oviva, and speaking or consultancy fees from Sanofi, Boehringer Ingelheim, and Fixing Dad (a low-carb app). Weiss reports having received research funding from the National Institutes of Health, Pfizer, and Lilly. He is an advisor to Virta Health and a co-founder and advisor to Keyto, Inc.