by Ya’el Courtney

In 2022, the majority of Americans (52%) followed a particular diet or eating pattern, primarily motivated by two things: a desire to protect long-term health and a desire to lose weight. According to data from the International Food Information Council, 23 million Americans chose to follow a ketogenic, or “keto”, diet last year to work towards these goals. This number has more than doubled since 2018, when only 10 million Americans chose keto. The business world has not missed this momentum – the keto diet market was valued at $10.22 billion in 2019 and is expected to grow 5.3% annually, reaching a value of $15.27 billion by 2027. It’s clear that the ketogenic diet is becoming increasingly popular, but should it be? Does it meet dieter’s main goals of long-term health and weight loss? Scientific research conducted over the last two decades says no, not really, and that this diet may be harmful for most people.

What is a ketogenic diet? 

Among dieting categories, methods that encourage low carbohydrate consumption and high protein consumption are increasingly popular. This includes things like Paleo, the South Beach diet, and the Atkins diet, which people sometimes mistakenly refer to as ketogenic diets. A true ketogenic diet is different. The ketogenic diet is a high fat, moderate protein, low carbohydrate eating pattern that differs from general healthful eating recommendations (set forth by the U.S. National Academy of Medicine) (Figure 1). Keto typically reduces total carbohydrate intake to less than 50 grams a day, with some people adhering to less than 20 grams a day. For context, one six-inch banana has 30 grams of carbohydrates, and one cup of cooked pasta has 45 grams. Keto dieters are encouraged to break down their daily caloric intake into approximately 70-80% fat, 10-20% protein, and 5-10% carbohydrates.

The ketogenic diet aims to induce weight loss by reducing the body’s supply of glucose, which is the primary source of energy for all cells in the body and is derived from consuming carbohydrate-rich foods. Instead, the diet encourages the production of an alternative fuel source called ketones from stored fat, hence the name “keto”-genic. The brain requires a steady supply of glucose, about 120 grams daily, and cannot store glucose. Therefore, when carbohydrate intake is minimal or during fasting, the body initially obtains glucose from liver stores. After 3-4 days, if stored glucose is depleted, the body enters a state called ketosis. During ketosis, the liver becomes able to produce ketone bodies, a type of fuel made from stored fat. In theory, the body will then eat away at its stored fat to meet its energy demands, leading to fat loss in an individual. 

Figure 1. Macronutrient composition by percentage of a regular diet vs. a true ketogenic diet (upper). Differential energy production pathways utilized on a regular diet vs. a ketogenic diet (lower). 

Is the keto diet effective for weight loss? 

While the theory behind fat loss resulting from a keto diet is appealing, it does not hold up well in practice. While keto dieters often experience a satisfying initial weight loss, this is a short-term result from the loss of body water that accompanies lower carbohydrate intake, not fat loss. This is because when we eat carbs, the energy that we do not use immediately is stored as glycogen molecules, and each gram of glycogen is stored with 3 grams of water attached to it. When you cut down on carbs, you quickly use up your glycogen stores, losing that water weight. Furthermore, the ketogenic diet’s restrictive nature makes it unlikely that people will follow it correctly, with over 50% of people failing to adhere to a ketogenic diet in many medical studies, which negates any short-term weight loss effects. Even if properly followed, a ketogenic diet is not intended to be adhered to long-term, nor is it uniquely effective. Studies show that after 6 months, a ketogenic diet does not lead to significantly higher weight loss than other weight loss approaches.

What health risks are associated with a ketogenic diet? 

So, if a ketogenic diet isn’t particularly effective for weight loss, how does it measure up to dieters’ second main objective: protecting long-term health and preventing future health conditions? Studies conducted over the last 10 years suggest that keto is likely riskier for most people than calorie-reduction approaches with moderate carbohydrate intake (Figure 2). 

First, while of course there is individual variability in food intake, the macronutrient ratios demanded by a ketogenic diet tend to lead to a general nutrient imbalance with glaring deficiencies. Many adherents curtail or eliminate fruits, vegetables, whole grains, and legumes while increasing consumption of animal products. This leads to deficiencies in thiamin, folate, vitamin A, vitamin E, vitamin B6, calcium, magnesium, iron, and potassium. These deficiencies can lead to a host of frustrating daily health issues. For example, common symptoms of potassium deficiency – referred to medically as hypokalemia – include constipation, heart palpitations, and extreme fatigue. Magnesium deficiency leads to fatigue, muscle twitches and cramps, apathy, and high blood pressure. Even when dieters focus on nutrient-dense foods, a ketogenic diet is reported to have multiple micronutrient shortfalls, often lacking in vitamin K, linolenic acid, and most water-soluble vitamins. Ketogenic diets are also typically low in the fiber needed for healthy intestinal function, nutrient absorption, and immune function. It is not yet known whether fiber supplements can counter these effects. Keto is also not conducive to optimal kidney function, as it significantly increases the occurrence of kidney stones. 

People who are pregnant or may become pregnant should be especially wary of following a ketogenic diet, as carbohydrate-restricted diets have been clearly associated with birth defects. This applies even if people follow carbohydrate-restricted diets before becoming pregnant and stop immediately upon learning they are pregnant. If the pregnancy was planned, people who followed keto in the year prior to conception were 30% more likely to have a child with a neural tube defect, specifically anencephaly or spina bifida. Additionally, in the 40% of pregnancies that are unplanned, there is an 89% increase in risk of neural tube defects if a carbohydrate-restricted diet was followed for the preceding year. This is likely related to decreased folate intake, since many carbohydrates are fortified with folate. 

Finally, a long-term health metric that many people who choose to lose weight are concerned about is cardiovascular risk, since it is well-established that obesity directly contributes to many incident cardiovascular risk factors. Unfortunately, emerging research shows that a ketogenic diet actually increases the risk of cardiovascular disease. In a young, fit population of CrossFit athletes, following a keto diet for 12 weeks led to an average weight loss of 6 pounds but increased “bad cholesterol” (LDL-C) by a whopping 35%. Typically, you would expect to see LDL-C levels drop when you lose weight. LDL-C has long been associated with cardiovascular risk because it forms arterial plaques (a cholesterol build-up in the inner lining of arteries), and emerging research that followed people for 12 years has now directly linked long-term ketogenic dieting with a 2x higher risk of heart disease or other negative cardiac events. More longitudinal research is being done on these risks, but many doctors are now stepping up and advising people to follow other weight-loss approaches to preserve their cardiovascular health. 

Figure 2. Graphic summary of long-term health risks associated with a ketogenic diet, including nutrient deficiencies, impaired intestinal function, increased bad cholesterol, increased risk of negative cardiovascular events, impaired kidney function, and birth defects. 

Is a ketogenic diet good for anyone?

Interestingly, the keto diet was not originally intended for the everyday dieter, as it was designed and used in clinical settings since the 1920’s to treat seizure disorders. Countless studies over the years support that keto often yields a significantly positive outcome for the treatment of refractory epilepsy in children and adults. Even in these cases, when it significantly reduces seizure incidence, keto is associated with adverse effects including dehydration, hypoglycemia (low blood sugar), lethargy, metabolic acidosis, gastrointestinal symptoms, and elevated cholesterol. However, the quality of life improvements brought about by seizure reduction are compelling enough for some patients to continue to follow the diet. 

Keto is being tested as an intervention for a host of other afflictions with mixed results. For example, this diet may be useful for the treatment, but not the prevention, of Alzheimer’s disease (AD). It seems to yield mild cognitive benefits for AD patients, though saturated fat intake, which typically increases on a ketogenic diet, is strongly associated with the risk of developing Alzheimer’s, and more research is underway to understand the nuances of this effect. It has been tried, but is now discouraged, for patients with Type 1 diabetes. Additionally, studies are underway regarding the impact of a ketogenic diet on Type 2 diabetes, non-alcoholic fatty liver disease, and a variety of cancers, but potential benefits remain unclear

Though more longitudinal studies are still being conducted, early conclusions already suggest that a ketogenic diet does more harm than good for almost everyone. Rather than a one-size-fits-all miracle weight loss approach, a ketogenic diet should be considered as a medical intervention only to be undertaken upon specific recommendation from a physician. 

Ya’el Courtney is a fourth-year PhD candidate in the Neuroscience program at Harvard University. You can find her on Twitter as @ScienceYael. 

Figures created with

Cover image by AbsolutVision on pixabay.

For more information: 

  • For a series of reviews from the Harvard T.H. Chan School of Public Health on the research behind popular diets, click here.
  • Check out a long-term weight management program created by a team of weight-loss experts at the Mayo Clinic that is generally safe for most adults here.
  • To learn about the history of the ketogenic diet, read this article.
  • To read about how the ketogenic diet might work to reduce seizures in patients with epilepsy, click here.

9 thoughts on “Keto – It’s Probably Not Right for You

  1. I’ve been carnivore for 6 months and have gotten off my meds, my cholesterol went to normal and my sugar is about back to normal. I’ve been diabetic for 20 years running in the 300s now I’m at 117 . Quit living to the American public to help big farms. Go watch Dr Ken Barry

  2. I’ve been on a low-carb diet to counter severe spinal arthritis inflammation and it began doing that after about three weeks. My daily pain level went from 7-8 to 1-2. Also, as a great side effect, I lost 50 pounds in about ten months. Unfortunately, I am dealing with long covid (9 months now) and I am not able to cook for myself so I purchase pre-cooked meals that are keto but higher than what I was making for myself. I am now in a carb maintenance mode so I am maintaining my weight. When I can begin to cook for myself again I will drop my total daily carbs as in this mode my daily pain level is higher.

    Sticking to keto and getting your daily nutrition is not difficult. I wish I had understood the interaction of carbs and inflammation years ago. Having a good electrolyte supplement is also a good thing on or off keto, one that also provides daily vitamin supplement.

    Anyone looking for quick fixes is bound to fail, but there are so many great keto cookbooks and so many great food options and nothing says you can’t take a few days off if you want (I did) and slide in and out of ketosis.

    This ís just my experience and opinion.

  3. I lost 63lbs in 5 months on keto and all of my metabolic numbers improved including A1C, total cholesterol, LDL, HDL, and blood pressure. If you are seriously obese or morbidly obese this is the program to follow. One can always transition to a more sustainable program once the desired fat lost is achieved. Like any program you can do keto well or poorly. Eat whole foods minimally processed and you’ll di exceptionally well on keto.

  4. If done CORRECTLY keto is a healthy way to eat. Majority of fat should come from fish..avocados..olive oil not from saturated fats. Diet should be supplemented with vitamins and minerals. When eating meat choose grass fed organic.

  5. So who funded this article or “research”? The sugar industry or perhaps coke cola or lays! I’ve lost over 60 pounds on keto. I was very strict at first and now eat real foods and nothing processed like sugar or chips.

  6. There are so many inaccuracies about the keto diet in this article. Please go follow an expert on the keto diet which includes more nutrition than any other diet out there, and of course you eat vegetables more than any other diet out there. This articles insane, I know so many people with diabetes that have stopped the need for medication with keto. As always, do the exact opposite of what these articles tell you. This is only an agenda to keep you from being healthy.

  7. I’d like help with getting started on the keto diet . Like how much fat and protein at each meal . I have fibro and the only time I feel good is after getting all the 💩 out of my system to have a colonoscopy. Is there someone on here that can teach me ? Without it costing an arm and a leg ?

  8. What a load of crap. Depressive mood went away just 2 months after going into intermitent keto (I eat fruits during weekend). I eat animal fat , nuts ,butter and you know what …. no nutrient defiency or unhealthy cholesterol/tryglicerides level has come up in the last two years; I got blood tests every month!!
    I got told off by several doctors, I show them my results and they think I lie….
    Keto not being effective for weight loss? Madame do your research…. it is the most effective diet… no low fat diet is more effective for this purpose than keto. I agree not everyone needs keto, but this article is so ill-informed…. you must have been dogmatized by Walter Willet and his feeble epidemiological findings.

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