[ kee-toh ]


, Chemistry.
  1. of or derived from a ketone.


  1. a combining form representing ketone in compound words:




  1. indicating that a chemical compound is a ketone or is derived from a ketone



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Word History and Origins

Origin of keto1

First recorded in 1910–15; independent use of keto-

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Example Sentences

Popular as the keto diet may be, there’s no evidence that a low-carb diet is any healthier than one that includes a balance of all macronutrients.

In a study he conducted, he found that energy expenditure increased 57 calories per day on the keto diet, although there was no accompanying fat loss.

This time, he compared a keto diet to a low-fat, high-carb plant-based diet.

The keto group lost more fat-free mass, but Hall points out that a big component of that is water, which you always lose when you cut carbs.

The keto diet was tied for second to last, with Whole30 just above it.

Around the time Elite took over,” she says, “I was put on a so-called keto diet.


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About This Word

What does keto mean?

Keto is short for ketogenic, referring to a diet that is low in carbohydrates but high in protein.

While originating as a medical diet, it’s popularly associated with weight loss.

Where does keto come from?

All protein and fat, all the time. That’s essentially the idea of the keto, or ketogenic, diet.

Ketogenic is the adjective of ketogenesis, a Greek-based word dating back to 1910–15 and literally meaning “producing ketone bodies.”

To put it simply, the keto diet has the body get energy from fat (which the liver converts into fatty acids and ketone bodies) rather than carbohydrates (broken down and stored as glucose). This diet dates to the 1920s; it was originally prescribed to help treat epilepsy.

The classic keto diet is medical and therapeutic, carried out in consultation with doctors and dietitians. It declined throughout the 20th century, but saw a revival after Hollywood director Jim Abrahams saw success with it in the 1990s in treating his son’s epilepsy.

In the health and wellness boom in the 2000s, keto has come to refer to a popular diet approach that’s low in carbs and high in fats and proteins. Leanne Vogel, for instance, published her popular cookbook, The Keto Diet, in 2017.

How is keto used in real life?

Keto can refer to the traditional diet as well as foods, recipes, and dietary approaches that are inspired by its general low-carb, high-fat/protein principles.

Outside of medical applications, mainstream followers of keto-inspired diets love it for weight loss. Others have criticized it as a fad—and some medical publications warn that it can cause problems if not properly applied. Always consult your physician, folks.

More examples of keto:

“… as a general weight-loss plan, keto is more controversial. Some health experts warn against it entirely, citing unpleasant side effects, health risks, and the diet’s unsustainable nature. Even many keto proponents admit that, if the diet’s not done “the right way,” it can be the opposite of healthy.”
—Amanda MacMillan, Health, October, 2018


This content is not meant to be a formal definition of this term. Rather, it is an informal summary that seeks to provide supplemental information and context important to know or keep in mind about the term’s history, meaning, and usage.