DEAR DOCTOR: I'm hearing a lot about the health benefits of a ketogenic diet, that it's great for weight loss and can even reverse diabetes. What is the diet, exactly? Are the claims true?
DEAR READER: The ketogenic diet, widely known as "keto," is an eating plan that switches an individual's main energy source from carbohydrates to fat. In its strictest form, 80 percent of calories come from fat, 15 percent from protein, and carbohydrates are limited to 5 percent of the total daily food intake. Considering that most Americans get about half of their daily calories from carbohydrates, 15 percent from protein, and about one-third from fat, keto basically flips the typical American diet on its head.
The name comes from the word "ketosis," the metabolic state that arises from this particular distribution of nutrients. When adequate carbohydrates are available, the body turns them into glucose, which it uses for energy. With carbs missing in action, the body switches to Plan B -- its stored fat. Burning that fat creates an energy source known as ketones. This shift takes place over the course of the first few days of limiting carbs to the 20- to 50-gram range. (Some dieters opt to jump-start the process with a 24- or 36-hour fast.)
People on a ketogenic diet eat mainly meat, fish, eggs, full-fat dairy, oils and low-carb vegetables, like leafy greens. Because of their high carb count, fruit, root vegetables, corn, grains, cereals and legumes don't make it onto the plate. Needless to say, pasta, rice, bread, and sweets become a thing of the past. In fact, with carbs restricted to about 20 grams per day, a single apple or banana will blow your carbohydrate budget.
While the extreme nature of the keto diet makes it sound like a fad, it was actually introduced in the 1920s to help children with medication-resistant epilepsy. Ongoing research suggests the diet may be neuroprotective, and scientists are looking into its potential to help patients with neurodegenerative diseases like Parkinson's and Alzheimer's disease.
You're right that the keto diet has been shown to improve glycemic control in people with Type 2 diabetes. Some patients do go on to reduce or even discontinue their medication. However, the diet's effect on blood chemistry can be extreme enough to require rapid adjustments in medication levels. People with Type 2 diabetes should not attempt it without a doctor's supervision. The diet is not recommended for people with Type 1 diabetes.
And while those on the keto diet experience rapid weight loss, they're also subject to constipation, electrolyte imbalances, nutritional deficiencies, poor mood and just plain boredom. Our main concern is the high fat content. Despite a dieter's best intentions to stick to good fats, the focus on high fat inevitably leads to excessive bad fat consumption. One of our patients wound up with LDL levels that doubled, which is never a good thing.
You've heard this from us before, but seriously, please check with your doctor before going keto. And if you do decide to give it a try, it would be wise to work with a nutritionist to craft the most well-rounded version of the diet possible.
Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.