What you need to know about the keto diet

By John Murphy, MDLinx
Published September 13, 2018

Key Takeaways

For the past year or so, the “keto diet” has been the latest fad diet to be popularized by health and fitness magazines and touted on social media. But what is the keto diet? Is it safe and, perhaps, even effective for your patients?

The keto—or ketogenic—diet is very low in carbohydrates, moderate in protein, and very high in fats. The “classic keto” diet consists of only 4% carbs, 6% protein, and as much as 90% fat. By starving the body of carbohydrates (ie, glucose, our typical energy source), the diet forces the body to burn fats as its main fuel. To get to this point, the body must not only use up its glucose, but also deplete its stored glycogen.

After a few days of strict dieting, the metabolism switches into a state of ketosis, in which it burns up fats at a high rate. The fats are then converted into fatty acids and ketone bodies, which are used as energy in place of the missing glucose. This is what gives the keto diet its reputation for fat-burning weight loss.

Origin of the ketogenic diet

But the diet didn’t start off this way. About a century ago, researchers confirmed that fasting reduced epileptic attacks in children. Because constant fasting is not exactly a great diet plan for anyone, endocrinologist and researcher Russell M. Wilder, MD, at the Mayo Clinic, Rochester, MN, proposed in 1921 that a ketogenic diet (a term he coined) could have the same effect as fasting in reducing epileptic attacks. The diet could be maintained for a longer period than fasting, too. This made it a popular treatment option for the management of epileptic episodes until newer, more conventional antiepileptic drugs came along, starting in the 1930s.

But does it work for weight loss?

Research shows that the ketogenic diet can accelerate weight loss. But the diet is meant to be followed for only a few weeks at a time, not year-round. So, whether patients can keep the weight off is another story. One meta-analysis found that people on a ketogenic diet did have long-term weight loss, but it was only about 1 kg (about 2.2 lbs).

These researchers concluded, “the present findings demonstrate that a [very-low-carbohydrate ketogenic diet (VLCKD)] has favorable effects on body weight and some cardiovascular risk factors…however, in the long term and when compared with conventional therapy, the differences appear to be of little clinical significance, although statistically significant. Healthcare professionals should weigh the advantages and disadvantages of recommending a VLCKD and consider their patients’ will power, since this therapy prominently alters an individual’s daily habits.”

Who shouldn’t be on a keto diet?

According to two recent studies, athletes and people with type 2 diabetes should probably avoid the keto diet.

In the first study, nutritionists at Saint Louis University, St. Louis, MO, studied the effect of the ketogenic diet on athletes. They found that the diet reduced exercise performance, especially for anaerobic activities. This finding has clear performance implications for athletes, especially those who participate in high-intensity, short-duration activities and sports.

“This diet is especially hot among people who are trying to optimize their health,” said study author Edward Weiss, PhD, associate professor of nutrition and dietetics, Saint Louis University. “What this study tells me is that unless there are compelling reasons for following a low-carb diet, athletes should be advised to avoid these diets.”

The second study, by researchers in Zurich, Switzerland, found that mice on a ketogenic diet had decreased glucose tolerance to a greater degree than mice fed a typical Western high-carb, high-fat diet.

“Although ketogenic diets are known to be healthy, our findings indicate that there may be an increased risk of insulin resistance with this type of diet that may lead to type 2 diabetes,” said corresponding author Christian Wolfrum, PhD, professor, Department of Health Sciences and Technology, Institute of Food, Nutrition and Health, ETH Zürich. “The next step is to try to identify the mechanism for this effect and to address whether this is a physiological adaptation. Our hypothesis is that when fatty acids are metabolized, their products might have important signaling roles to play in the brain.”

The bottom line?

“Instead of engaging in the next popular diet that would last only a few weeks to months (for most people that includes a ketogenic diet), try to embrace change that is sustainable over the long term,” recommended primary care physician Marcelo Campos, MD, on the Harvard Health Blog. “A balanced, unprocessed diet, rich in very colorful fruits and vegetables, lean meats, fish, whole grains, nuts, seeds, olive oil, and lots of water seems to have the best evidence for a long, healthier, vibrant life.”

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