In recent years, the “keto” diet has attracted millions of people looking to lose weight and reap its other purported benefits. So, are they onto a cutting-edge biohack? Or dangerously misguided, trading short-term results for long-term misery?
What is the Ketogenic Diet?
There are a few different kinds of ketogenic diets (more on that later), but what they all have in common is a severe reduction in carbohydrate intake, putting your body into a metabolic state known as ketosis.
Ketosis occurs when your body metabolizes fat rather than carbohydrates to produce energy. This process produces ketones — a type of acid — in your blood as a by-product.
It’s actually pretty cool that our bodies can do this. It was once a useful survival tool for our ancestors.
We wouldn’t have made it as a species without our body’s ability to temporarily use fat when we couldn’t find enough carbohydrate-rich foods. Stored fat got our ancestors through hard times when food was scarce and provided a buffer when they had to go days without eating.
As this process existed as an evolutionary tool, there’s even evidence that challenging the body through fasting-induced ketosis every so often yields health benefits. The fancy term for this phenomenon is “hormesis,” meaning certain stressors in certain doses at certain intervals can actually make us stronger. (Lifting weights to break down muscle fibers is a familiar example of hormesis in action.)
But the modern ketogenic diet movement, as we know it, doesn’t typically focus on temporary or intermittent fasting as a survival tool. The keto diet seeks to keep the body in a permanent state of ketosis by severely restricting carbohydrates and compensating with loads of fat and protein as an energy source.
So what exactly do you eat on a ketogenic diet, and what are you supposed to avoid?
Foods Not Allowed on a Ketogenic Diet
Carbohydrates are the enemy on a keto diet. That includes sugary foods, grains and starches, alcohol, most fruit, beans and legumes, root vegetables and tubers (e.g., sweet potatoes, beets, carrots), low-fat or diet products, and some condiments or sauces. In fact, your carbohydrate consumption might be less than you’d derive from a single apple a day.
But a ketogenic diet doesn’t distinguish between “good carbs” like lentils and “bad carbs” like lollipops.
While it’s great that it eliminates refined sugar, white flour, and many processed foods, keto also forbids some of the healthiest foods on the planet.
Avoiding whole, plant-based carbs like fruit, legumes, and grains means that you’re likely to be dangerously deficient in antioxidants, phytochemicals, vitamins, and minerals, all of which are important for disease prevention and long-term health.
You’ll also likely miss out on adequate fiber, which is no small matter. About 97% of the US population is already deficient in fiber, which puts you at increased risk of heart disease and several digestive cancers, as well as breast cancer.
So What Can You Eat On A Ketogenic Diet?
Keto-compliant foods include meats, fish, eggs, butter and cream, nuts and seeds, vegetable oils, avocados, low-carb veggies (e.g., lettuce, zucchini, and peppers), and certain condiments.
Eating plant-based fats from nuts, seeds, and avocados does make good sense. And plenty of studies show us that low-carb vegetables (like leafy greens) are terrific health boosters. The problem is that, for most keto diet adherents, a majority of their calories typically come from animal products.
Given the overwhelming body of evidence linking consumption of meat and other animal products to cancer, Alzheimer’s, and heart disease, the fact that keto diets typically rely heavily on animal products seems like a recipe for long-term health problems.
Types of Ketogenic Diets
There are five main types of ketogenic diets:
- The standard ketogenic diet is a very low-carbohydrate, moderate-protein, high-fat diet. These macronutrients make up 5%, 20%, and 75% of the diet, respectively. However, fat content may be increased to as high as 90%.
- The cyclical ketogenic diet includes higher carbohydrate days to refeed your body. For example, you might follow the standard ketogenic diet for five days, followed by two days of high-carbohydrate intake.
- The targeted ketogenic diet allows you to eat more carbohydrates around exercise to help fuel your workouts.
- The high-protein ketogenic diet is similar to the standard version but emphasizes protein even more, with a ratio of 35% protein, 60% fat, and 5% carbs.
- And the plant-based ketogenic diet relies heavily on high-fat plant foods such as nuts, seeds, avocados, coconut, and bottled oils, in addition to relatively low-calorie greens.
Standard and high-protein ketogenic diets are the most common, while the cyclical and targeted varieties are used mainly by athletes.
And while a plant-based keto diet may sound nice to folks who choose to avoid animal products, it can be quite limited, and as such, may wind up leading to deficiencies in a number of antioxidants, vitamins, phytochemicals, and other nutrients that are important for long-term health.
What are the Risks of a Ketogenic Diet?
“Keto Flu”
When beginning a ketogenic diet, some people may experience a set of symptoms dubbed the “keto flu.”
These symptoms can include, but are not limited to:
- Nausea
- Vomiting
- Constipation
- Diarrhea
- Headache
- Weakness
- Fatigue
Symptoms usually last about a week as the body adjusts to the lack of carbohydrates.
Due to possible symptoms of the keto flu, such as diarrhea and vomiting, and because most initial weight loss on a keto diet is water weight, hydration (with electrolytes) is especially important.
Nutrient Deficiencies
Animal products have zero fiber, so we need to rely on plants to get our fiber. But since the keto diet relies so heavily on fat and restricts all carbs, including fruits and vegetables, it can be a recipe for developing nutrient deficiencies.
Fiber itself is an essential nutrient, particularly prebiotic fiber, which feeds the good bacteria in your gut. But it also helps your body absorb nutrients from food and eliminate waste and toxins.
Fruits and vegetables contain high amounts of fiber, vitamins, minerals, antioxidants, and phytochemicals — many of which are not present at all in animal products or high-fat foods.
High-carb foods like beans, bananas, and oats also contribute to your body’s electrolyte stores, which are more easily lost on the keto diet from excess water extraction. And a lack of these and other nutrients has been shown to contribute to a variety of chronic diseases such as heart disease, osteoporosis, cancer, and mental health disorders.
Real-world low-carb/keto patterns are associated with micronutrient gaps, likely due to reduced intake of fruits, legumes, and whole grains.
Disease Complications or Death
Not to scare you, but the ketogenic diet has been shown to increase the risk of disease complications, and even (for some people) premature death.
People with diabetes can have a more severe type of ketosis called ketoacidosis if they don’t have enough insulin. Ketones build up and change the chemical balance of their blood. The combination of acidity in the blood and dehydration from fluid loss can cause organ damage, coma, or death.
And in 2018, the European Society of Cardiology found that people who followed a low-carb diet had the highest risk of overall cardiovascular, cerebrovascular (like stroke), and cancer death.
The ketogenic diet is also not recommended for patients with pancreatitis, liver failure, disorders of fat metabolism, or kidney disease because of certain long-term recorded effects, such as fatty liver disease, kidney stones, and dehydration-related symptoms, which may complicate these diseases.
Positive Uses of the Keto Diet
Epilepsy
The keto diet has been successfully used to treat intractable epilepsy in children since the 1920s. But the original ketogenic diet fell out of use after World War II with the development of more effective anti-epileptic drugs. Then, interest was revitalized again in the 1990s thanks to an epileptic boy named Charlie Abrahams.
Charlie had up to 100 seizures a day with no relief from medication until his parents learned about the diet in a medical textbook. His seizures stopped almost immediately, and he remained on the diet for five years.
In 1994, Charlie’s family created The Charlie Foundation for Ketogenic Therapies, which helped spread awareness about the diet and assisted other children with epilepsy.
Although the ketogenic diet has been used to treat children with epilepsy and shows some promise, it’s rarely recommended because of how strict it is. It’s generally only prescribed in severe cases of epilepsy and only under the care of both a medical doctor and a dietitian.
Weight Loss
The most common reason people go on a keto diet is to achieve rapid weight loss.
In the US, nearly three-quarters (73.6%) of adults are overweight or have obesity, including 40.3% who are classified as having obesity, which is correlated with a higher risk of nearly every major chronic disease of our times.
And keto diets can be effective at helping people lose weight — at least in the short run.
Studies show faster weight loss when people go on a keto diet, compared to those on a more traditional low-fat or Mediterranean diet. However, that difference in weight loss seems to disappear over time. After two years, the dietary approaches yield similar weight-loss results.
Furthermore, keto diets have not been studied long-term. Since many health conditions take years to develop, a full understanding of the effects of a keto diet (or any diet for that matter) will require studies that last decades, not months.
Diabetes
People with type 2 diabetes who go on ketogenic diets often show improvements in glucose levels and biomarkers for blood sugar stability. But in these studies, subjects are essentially starved of food, sometimes only ingesting 650 kcal/day. Is it the ketosis or the caloric restriction that’s the important factor?
In addition, there’s a profound difference between managing biomarkers and addressing the underlying metabolic dysfunction that exists in diabetes. Cut out all starchy foods — grains, legumes, fruits, starchy veggies — and the biomarkers that can get out of whack in response to stimulation from these foods may look fabulous. However, diabetes still exists — it’s just not showing up in the biomarker numbers because you’re not eating the foods that would show the insulin resistance.
This is a bit like “fixing” a clogged sink drain by no longer using the sink rather than removing the blockage. As long as there’s no water running down the drain, the sink looks fine. But that doesn’t address the real problem.
The same is true with carbs. If you don’t eat carbs, your blood glucose levels will drop. But the real measure of insulin sensitivity is being able to eat carbs and process them healthfully. And there’s nothing about the keto diet that helps that to happen.
In fact, to the contrary, a growing body of research shows us that a diet high in animal products, as most keto diets are, leads to higher rates of type 2 diabetes. And recent human data suggest that very low-carb, high-fat (keto-style) patterns may raise long-term risk of type 2 diabetes, especially when carbs are replaced with saturated fat, rich animal foods.
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Keto for Cancer?
There’s a popular theory fueled by the controversial research of Dr. Thomas N. Seyfried and the book, Keto for Cancer, that the keto diet can help fight cancer.
Dr. Seyfried’s theory is that cancer is a metabolic disease and, therefore, a low-carb, low-calorie diet will starve cancer cells of their supposed fuel. In his words, “Nutritional ketosis induces metabolic stress on tumor tissue that is selectively vulnerable to glucose deprivation.”
While nutrition does influence cancer growth, cancer cells don’t just eat sugar. A 2016 study published in the journal Nature showed that high-fat diets, especially from animal products and processed oils, actually fed cancer tumors and initiated their spread throughout the body.
Additionally, cancer can actually feed on ketones, causing tumors to grow and metastasize. In fact, a 2012 study concluded that ketone inhibitors should be used to treat cancer patients, especially those with repeated cancer growth and metastasis.
Weight Loss
There is not now, nor do we have a record of there ever having been, a human population anywhere in the world eating a keto diet and experiencing long lifespans. To the contrary, a 2018 study published in The Lancet concluded that people who eat low-carb diets have shorter lifespans (by an average of four years). The authors write:
“Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality…”
And in another 2018 study published by the European Society of Cardiology (also referenced in the “Disease Complications or Death” section of this article), researchers found that, during the course of the study, people who ate low-carb diets had a 32% increased risk of death from all causes when compared to those eating the highest amount of carbs. Specifically, low-carb eaters suffered from a 51% higher risk of dying from heart disease and a 35% higher risk of dying from cancer.
A 2024 systematic review in The American Journal of Clinical Nutrition reports that ketogenic diets often raise LDL cholesterol and ApoB (particles that can cause plaques in the arteries), both of which are associated with poor cardiovascular health.
The Verdict on Ketogenic Diets
The ketogenic diet originated as, and still is, a medical diet that may be helpful for epilepsy. And it can lead to rapid weight loss in the short term. However, starvation and illness can also cause weight loss, but that doesn’t make them healthy ways to achieve it.
There are currently no studies showing that a ketogenic diet benefits long-term health. In fact, multiple studies show that such low-carb, high-fat diets can actually lead to shorter life expectancy and higher rates of disease.
Ditching processed foods, refined carbs, and added sugars can do wonders for your health, and the keto approach gets that right. But you can do all of that without basing your diet around animal products and high-fat foods.
After all, a whole food, plant-based diet with lots of delicious fruits, vegetables, legumes, nuts, seeds, and whole grains can also lead to weight loss. And in the process, it will also help your body fight and prevent cancer, heart disease, obesity, Alzheimer’s, type 2 diabetes, and virtually every other major chronic illness of our times.
Tell us in the comments below:
- Are you on the keto diet, or are you considering it?
- What do you think about the ketogenic diet?
Featured Image: iStock.com/ThitareeSarmkasat
