Food matters

The keto diet: 5 fast facts

This popular diet has been used to treat epilepsy and may improve insulin sensitivity, but it has its downsides, too.


The ketogenic diet is an ultra-low-carbohydrate, high-fat diet that has been used for decades to treat certain medical conditions. Today, adherents claim that it will help you drop pounds while boosting your energy levels and controlling your blood sugar. Its promise of fast and aggressive weight loss is a compelling one in our world of quick fixes, but the ketogenic diet can be complicated in its execution and the research of its long-term benefits and drawbacks is ongoing.

Colin Zhu, DO

“Most people’s expectations are to lose weight with this diet. However, whether this is a sustainable strategy has yet to be determined. I advocate for whole health and taking care of all aspects of it, not just dropping weight,” says Colin Zhu, DO, a family physician who specializes in lifestyle medicine.

Here are five fast facts about the ketogenic diet—including its pros and cons.

    1. Burning fat: On most diets, the body uses glucose as its primary energy source. The ketogenic diet essentially forces the body to use fat as its main source of energy instead. It does this by mimicking a state of starvation where the body breaks down fat stores and converts them into ketones through a biochemical process called ketosis.
    2. Reaching ketosis: Generally speaking, the ketogenic diet is composed of 70-75 percent fat, 20-25 percent protein, and 5-10 percent carbohydrates. This strict formula is the key to ensuring a person enters the metabolic state of ketosis, which isn’t necessarily easy. In fact, reaching and maintaining ketosis can be exceptionally challenging for many people and requires diligence and planning. Newbies to the keto diet may experience symptoms such as dizziness, headaches, brain fog, nausea and irritability, says Dr. Zhu. This is sometimes referred to as “the keto flu.” These side effects generally go away after several weeks once someone becomes “keto-adapted.”
    3. Nuts and bolts: Foods to be limited on the ketogenic diet include: whole grains; beans and legumes; starchy vegetables like yams and potatoes; high-carbohydrate fruits like apples, oranges and bananas; alcohol; sugar; and low-fat dairy products. The keto diet does promote eating meat from various sources, as well as eggs, fish, avocados, coconut and olive oils and non-starchy vegetables.
    4. The good: Beyond weight loss, the ketogenic diet has been in use for conditions like epilepsy since the 1920s and obesity treatment since the 1960s.“ The keto diet really alters energy metabolism in the brain, so that’s why it’s thought to stabilize the functions of the neurons exposed to seizures in people with epilepsy,” says Junella Chin, DO, who uses the keto diet as a tool for treating children with intractable epilepsy in her integrative medical practice. “It helps children with seizures decrease their episodes and shorten their recovery time from seizures.” The keto diet has also been implicated for therapeutic use in chronic diseases such as heart disease, neurological conditions, polycystic ovary syndrome, and cancer. There’s also limited evidence that insulin sensitivity improves on the diet, which bodes well for managing diabetes.
      Junella Chin, DO
    5. The bad: The downside of a ketogenic diet is that there is no well-established evidence to support its sustainability on a long-term basis, and further well-controlled trials are recommended, says Dr. Zhu. Recent research published by The Lancet found that restricting carbs and replacing them with animal-based protein and fat could lead to a shorter lifespan. For children with epilepsy, the biggest challenge of the keto diet is compliance, says Dr. Chin. “We struggle with compliance with kids and then parents because, of course, parents need to be on board too. And constipation can be a really big side effect that deters compliance.”

Stay tuned

While studies of the ketogenic diet have shown short-term benefits for people that include weight loss and improvements in blood sugar and blood pressure, the jury is still out on whether these benefits can be sustained long-term.

“The ketogenic diet has the potential to be a game-changer,” says Dr. Zhu, “but a lot depends on whether its benefits pan out in large-scale trials and whether individuals can tolerate its dietary restrictions over the long haul. People struggling to lose weight for health reasons should keep it on their radar and stay tuned for more conclusive information.”

Further reading

Half failed this nutrition quiz. Can you pass it?

5 myths about whole-food plant-based diets debunked

Let’s talk about nutrition: 4 ways to advise your patients on what to eat


  1. Michael Nigro,D.O.

    Having used the ketogenic diet to treat intractable epilepsy in 200+ children I can attest to its effectiveness but also point out the potential problems of compliance weight loss hypercholesterolemia ,and rare sudden unexpected medical crisis. A skilled dietitian should be involved. Important to recognize that the concept evolved from the success of an Osteopathic physician who successfully treated epilepsy in 1920’s. His work was studied by Johns Hopkins and Mayo clinic doctors.

  2. James Schmitz D.O.

    Article is full of nonsense statements like “Lancet found that restricting carbs and replacing them with animal-based protein and fat could lead to a shorter lifespan.”
    Where is the evidence of this? If you are lowering Blood Sugar, Blood Pressure, and hyperinsulinemia then it is much more likely to be increasing lifespans. When you paint with a broad brush like the statement above it needs to be backed up with reliable facts before making it. Show us the research reported in the Lancet to back this statement up.

  3. R Colucci, DO

    I love the media hype of “diets” that have been around forever and certain physicians acting like they are pioneers in nutritional science. The ketogenic diet, so called, has been in use for decades. This diet was used in the day primarily by fashion models and starlets in Hollywood who had to drop weight/body fat and by athletes as well, in particular, body builders. The biggest issue with this diet, longer term, is the “brain fog” where concentration is more difficult and short term memory is impaired. This is due to the brain’s preference for glucose as a fuel vs fatty acids. The majority of folks that are on this diet and who are truly in ketosis never overcome this shortcoming causing its cessation. It is also a difficult diet to sustain due to severe CHO craving. It can be an excellent short-term diet for T2D who have had constant “insulin creep” (as I call it) where the amount of insulin used has gradually increased over time to cover rising blood sugars. Insulin requirements plummet and weight loss being achieved to some degree while giving the pancreatic islet cells a rest. Again, due to the difficulty of sustaining this diet, pts fall off or are slowly removed from it by 2-3 months in, usually to the point where ketosis has ceased but where the insulin requirement is much less. This strategy takes careful planning and diabetologists or endocrinologists working with an RD is the best way to attain the goals of wt loss and stopping insulin creep.

  4. Joseph C. Benedetto, D.O.

    The Lancet article is a population study which is great for generating hypotheses but not conclusions. As to the amount of carbohydrate consumed by the “low carbohydrate group,” this was nearly 50% of total caloric intake. I don’t think one can extrapolate to a ketogenic diet at this level of carbohydrate intake. Finally, “the participants who consumed a relatively low percentage of total energy from carbohydrates”…”were more likely to be young, male, a self-reported race other than black, college graduates, have high body-mass index, exercise less during leisure time, have high household income, smoke cigarettes, and have diabetes.” That is, were more likely to have other risk factors for early mortality.

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  8. Martin connarton

    Very lucid and helpful well-organized article on the keto approach and its complexity thank you so much for your sound work on this difficult subject Martin connaughton clinical social worker and drug and alcohol counselor in New Hampshire and Massachusetts thank you so much the article was logical clear and very helpful piece

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