A physician’s warning on the keto diet


The keto diet has recently garnered much fame for its apparent ability to improve diabetes and obesity – results so impressive the Journal of the American Medical Association recently highlighted the diet and thereby christened it as something more than a low-carb craze. However, not all the evidence supports such a positive outlook, leading the diet to straddle the increasingly blurred lines between faddist snake oil and sanctified medical therapy.

For starters, the keto diet is not new. Nearly a century ago, prior to the discovery of insulin by Frederick Banting and Charles Best, the keto, or ketogenic, diet was used as a crude way to stave off high blood sugar levels, which was then inevitably fatal. By foregoing carbohydrates, the body utilizes fat, either stored or consumed, as its main energy source without raising blood sugar levels. In the process, ketones are produced, and thus giving the diet its name.

By avoiding carbohydrates altogether, blood sugar levels do no spike, but the underlying glucose resistance may still be present. Although some small non-randomized studies show improvements with the diet, a larger meta-analysis of diabetic patients on either the ketogenic diet or a high-carbohydrate, low-fat diet for more than one year showed no difference in hemoglobin A1cs or glycemic levels between the two diets. If the diet produces results no different than a high-carbohydrate, low-fat diet, then what about its effects on weight loss?

The diet’s initial ability to induce weight loss may non-trivially be related to its ketone production. Since ketones are osmotically active, they can induce a diuretic-like response, causing dieters to lose fluid-related weight, especially during the beginning of the diet. Those early results can serve to positively reinforce dieters and may be crucial in deciding whether to continue dieting, particularly in the face of restrictive dietary options and the malaise associated with the transition, dubbed “the keto flu,” which includes a combination of gastrointestinal distress (especially constipation given the lack of fiber), cramps, dizziness, brain fog, mood disturbances, and/or insomnia.

Long-term weight loss on the keto diet is less mystical than its powers to reduce blood sugar levels: It’s the product of devoted caloric restriction. During the zeitgeist of the last low-carbohydrate craze, which encompassed the Zone, South Beach, Atkins, Paleo and Dukan diets, researchers found that, “In all cases, individuals on high-fat, low-carbohydrate diets lose weight because they consume fewer calories.” Many of the studies done regarding weight loss on the keto diet, including several mentioned in the JAMA article, conspicuously fail to mention daily calorie intake, raising the diets panacea-like allure. However, a closer look shows that these diets are not much better than a low-fat diet. An oft-cited meta-analysis comparing low-carb ketogenic diets to low-fat diets showed a difference in weight-loss of less than a kilogram after twelve months – a negligible difference. Interestingly enough, another, more-recent, meta-analysis showed no difference in results between low-carb and high-carb diets on weight – or blood sugar levels – after one year.

Proponents of the keto diet will maintain that it can be used for the treatment of obesity and diabetes. But, is it safe? Does the risk of taking on a new diet with safety concerns justify the loss of a few or more pounds? It might if you are so obese or diabetic that you suffer from complications of those diseases, as almost anything will be better than suffering a heart attack or an amputation from diabetes. But perhaps not if you don’t have those comorbidities.

One of my concerns is the unnaturally high amount of fat consumed to maintain ketosis. If the diet had another name, it would be called “the fat diet” as 70-80 percent of calories per day come from fat. The only native population eating this much fat were the Inuit, who were forced to subsist on blubber out of necessity. And perhaps because of the high amounts of saturated and trans fats consumed, the Inuit experienced – despite popular misconceptions – a higher rate of heart disease, strokes, and death compared to non-Inuit and Western populations. The opportunity cost of not eating fruits, vegetables, and complex carbohydrates may have also contributed to their heightened risk.

Currently, there is no long-term data on the safety of the keto diet in adults. The keto diet may not be worth pursuing, even for diabetics or the obese, if we are mortgaging those diseases for higher rates of heart disease or colon cancer, a possibility given the low amounts of fiber consumed on these diets. More, we already know that the diet has not been without consequence for pediatric patients treated with it for refractory epilepsy, which has been ongoing since the 1920s.

From this population, children have developed kidney stones, acidosis, fractures and stunted growth. At the more serious end of the spectrum, children on the diet have died from arrhythmias arising from selenium deficiency and pancreatitis. The possibility of these side effects and possibly others yet to be discovered may tilt the diet out of favor.

However, deliberation over the keto diet or other low-carb diets is often omitted for the purposes of a near-Machiavellian attainment of weight loss or some other health goal. Before embarking on a diet with known adverse effects in children, uncertain long-term safety in adults, and equivocal benefits when compared to other dietary strategies, both patients and physicians alike would behoove themselves to remember that diabetes and obesity are not a product of ketone deficiency but the symptom of caloric excess, dietary indiscretion, and torpor. Let food be thy medicine – but not if it involves a Faustian bargain of your health.

Shivam Joshi is a nephrology fellow. He can be reached on Twitter @sjoshiMD and on Facebook

Image credit: Shutterstock.com


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