Myths & Facts

Fact:

Numerous studies show that the ketogenic diet has helped athletes improve their body composition, trim fat, maintain performance and improve recovery. These studies have included marathon runners,¹ triathlon competitors,² CrossFit athletes,³ gymnasts,⁴ and other athletes performing high intensity⁵ and interval⁶ exercises.

One study found that after 12 weeks eating a ketogenic diet, endurance athletes cut body fat, increased oxidation and sprint power, and performed better overall on a critical power test compared to athletes on high-carb diets.⁷

Fact:

The ketogenic diet has actually been endorsed by the American Diabetes Association as the best diet to control blood sugar for people with Type 2 diabetes. Some studies have shown that extreme caloric restriction can also reverse diabetes, but continued starvation is largely unsustainable.

No other diet has demonstrated more promising results for Type 2 diabetes than one very low in carbohydrates.

Upwards of 17 scientific studies⁸ support the idea that carbohydrate restriction works to manage blood sugar, or glycemia, in patients with diabetes.

Fact:

Upon starting the diet, some patients report symptoms like fatigue, headaches, and muscle aches. However, these short-lived symptoms are, in fact, a sign that the diet is working, and the body is switching over from burning glucose as fuel to burning fat. This transition involves upregulating certain enzymes and down-regulating others; it is a profound shift for the human body that can have uncomfortable symptoms. However, these side effect usually last only 3-4 weeks.

Fact:

While it’s true that low-carb diets do raise the so-called bad LDL-cholesterol in some people, it’s important to note that LDL-C, when influenced by diet, has never been shown to have any effect on cardiovascular risk.

More importantly, the ketogenic diet also reliably raise the “good” HDL-cholesterol, while also improving most other cardiovascular markers, including blood pressure, as this study shows.⁹ Thus, the overall effect on cholesterol and other markers for heart disease is positive.

Fact:

One study¹⁰ found carbs to be the “main culprit” in causing acne. However, another study found that low-glycemic diets lessened acne.¹¹What’s more, a review¹² conducted by Italian researchers suggested that the keto diet could target acne by reducing inflammation and levels of insulin and IGF-1 — all known causes of acne.¹³

Fact:

Patients with gastroesophageal reflux disease (GERD) have been shown to improve after eating very low carbohydrate diets.^{14, 15} Another study found increased carb-intake worsened GERD, while a high-fat, low-carbohydrate diet reduced symptoms.¹⁶ And two studies have linked esophageal diseases, including Barrett’s esophagus (BE)¹⁷ and GERD,¹⁸ to sugar and carbohydrate intake.

Fact:

The European Association for the Study of the Liver actually cites a low-carbohydrate diet as a way to treat the disease.¹⁹ Studies show that cutting carbohydrates²⁰ and particularly fructose,²¹ or sugar from plants, works to improve liver fat metabolism.

What’s more, high-carbohydrate diets have been associated with worsening non-alcoholic fatty liver disease. Find evidence here,²² here²³ and here.²⁴

Fact:

There seems to be no foundation for this claim. People eating diets very low in carbohydrates and high in fats and proteins have been found, in one study,²⁵ to enjoy better sleep quality, meaning they spent more time in deep sleep than those on high-carbohydrate, low-fat diets. A survey of 1,580 low-carb consumers published by the Journal of Insulin Resistance²⁶ found that while more than 11% of respondents reported using sleep-aids before beginning their low-carb diet, less than 5% reported using them after their diet.

Fact:

Multiple studies have found that diets higher in fat prevent gallstone formation. Examples are here²⁷ and here.²⁸ Meanwhile, diets low in fat actually increase gallbladder volume²⁹ and may increase the risk of gallstone development, as do diets high in sugar and carbohydrates.³⁰

Fact:

Studies have demonstrated that the keto diet may in fact be ideal for long term weight management. One meta-analysis³² found that individuals following very low-carbohydrate ketogenic diets lost more weight in one year than those on low-fat diets.

A survey published in the Journal of Insulin Resistance³³ found that three of four respondents on a low-carb diet reported losing 10 pounds or more; one-third reported losing more than 30 pounds. Six out of 10 respondents who were on the diet two years or more reported losing 20 pounds or more and 46% said they lost 3 inches from their waists.

Fact:

The ketogenic diet does not limit calories; people can eat as much as they like so long as they restrict carbohydrates. This means that people don’t have to endure long periods of feeling hungry—which is why the ketogenic diet tends to be sustainable.

The survey in Journal of Insulin Resistance found that before respondents started their low-carb diets, nearly nine of 10 experienced intense hunger between meals. Once on the diet, only 3.5% said they grew hungry between meals. Respondents reported similar improvements in other aspects of their physical and psychological well-being.³⁴

Of the 1,580 survey participants, more than half reported staying on a low-carb diet for at least one year, and 34% reported more than two years. Further, those on the diet for two years or more said that they had largely maintained their weight loss.

Fact:

The widely reported Lancet Public Health study ³⁵ that made this claim is based on very thin data. The questionnaire underlying the report left out questions regarding popular foods, such as pizza and energy bars, and did not consider alcohol consumption. Moreover, the “low-carb” diet group in this study included people eating up to 37% of calories as carbohydrates—not low-carb according to the latest science. Ultimately, this is the kind of data that can show association but not establish causation, which means it is the kind of data one can use to generate hypotheses but not prove them. This kind of data would never be considered sufficient to approve a drug, for instance. The same standards should be applied to diet. Quite a few researchers had their critiques published in Lancet Public Health.³⁶ The authors replied but did not respond to most of the criticisms.

Meanwhile, more than 70 trials have examined the health effects of a low-carb diet. They attest to the benefits³⁷ associated with ketosis and low-carb diets, including a reduction in body weight and body mass index, improved cardiovascular risk factors including blood pressure, and the reversal of Type 2 diabetes. It is virtually impossible to imagine that a diet with so many health improvements in the ‘near term’ (2 years) could ultimately shorten life—and the study authors offer no possible mechanism to explain how this might happen.

The larger question is why we are seeing such a sudden rash of anti-keto stories. So many of them quote no experts sources and do not provide citations for their claims. Skeptics with little acquaintance with the diet are quoted exclusively instead. From a journalistic perspective, this lack of balance of viewpoints and the failure to back up claims with evidence falls below basic reporting standards. Offenders on this list include even the Harvard School of Public Health, which recently published more than one  unsourced, one-sided article on the keto diet (This is in addition to the Lancet Public Health article cited above, by Harvard researchers, which suggests that a low-carb diet kills you). These stories could reflect lazy reporting or they could very well be scare tactics to steer people away from the keto diet. Now why would reporters or scientists at Harvard be doing such a thing?