In 2018, “keto” was the most Googled diet and food category in the world. This
way of eating has attracted millions of people looking to lose weight and reap
its other purported benefits. So, are they on to a cutting-edge biohack? Or
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. This puts your body into a metabolic state known as
Ketosis occurs when your body metabolizes fat, instead of
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. When food was scarce, our ancestors got through hard times due to stored
fat, which provided a buffer when they went 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
So is the keto diet healthy? What exactly do you eat on a
ketogenic diet? And what foods do you avoid?
Foods Not Allowed on a Keto Diet
Carbohydrates are the enemy on a keto diet. Foods not
allowed on a ketogenic diet include 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 entire 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. And all of these 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. This puts you at increased risk
of heart disease and several digestive
cancers, as well as breast
So What Can You Eat On A Keto Diet?
Keto-compliant foods include meats,
fatty fish, eggs,
butter and cream, nuts and seeds, vegetable oils, avocados,
low-carb veggies (e.g., lettuce, zucchini, and peppers), and certain
Eating plant-based fats from nuts, seeds, and avocados
makes good sense. And plenty of studies show us that low-carb
vegetables (and actually, pretty much all fruits
and veggies) are terrific health boosters. But as you can see, most of the
calories of keto eaters 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 most keto diets 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, you can consume as
much as 90% fat.
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 focuses even more on protein intake
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 & high protein ketogenic diets are the most
common; cyclical and targeted are mainly used by athletes.
While a plant-based keto diet may sound nice to folks who
are grossed out by the notion of basing their diet around animal products, it
often derives a surprising amount of calories from fish or other meats. Vegan
keto eaters tend to eat large amounts of nuts, oils, avocados, and coconut. And
they may still be deficient in any number of antioxidants, phytochemicals,
fiber, and other nutrients that are important for long-term health.
What are the Risks of a Ketogenic Diet?
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:
Symptoms usually last for around a week or so as the body
adjusts to the lack of carbohydrates.
Due to possible symptoms of keto flu, such as diarrhea and
vomiting, along with the fact that most of the initial weight loss on a keto
diet is water weight, hydration (with electrolytes) is especially important.
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. Prebiotic fiber feeds the
good bacteria in your gut. And 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. And you won’t find many of these nutrients in animal
products or high-fat foods.
High-carb foods like beans, bananas, and oats also
contribute to your body’s electrolyte stores. These 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.
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)
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.
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
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
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
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
In 1994, Charlie’s family created The
Charlie Foundation for Ketogenic Therapies. The foundation helped spread
awareness about the diet and assist 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 dietician.
Nearly 70% of all Americans are overweight or obese. Obesity is correlated with a
higher risk of nearly every major chronic disease of our times.
The #1 thing that people go on a keto diet for is rapid
weight loss. And research tells
us that keto diets can be effective at helping people lose weight — at least in
the short run.
In fact, when you compare to those on a more traditional
low-fat or Mediterranean diet, studies show faster weight loss when people go
on a keto diet. However, that difference in weight loss seems to disappear over time. After two years, the
dietary approaches yield similar weight loss results.
Furthermore, there has been very little study conducted on
keto diets over the long-term. If you want to see the effects of diet on
disease, you need to study people over decades because most health problems
take years to develop.
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.
And 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, the 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 taking a bad driver off the road. They
won’t get any speeding tickets, but that doesn’t make them a safer driver. It
just means they’re no longer “in the game.” 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 a keto diet might even cause type 2 diabetes, according to some recent
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. He states “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. A 2012 study concluded doctors
should design ketone inhibitors to treat cancer patients, especially those with
repeated cancer growth and metastasis.
Keto and Life Expectancy
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, in a 2018 study published
in The Lancet, researchers 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 (which we also referenced in the Disease Complications or
Death section of this article), researchers found that 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. The researchers also learned that low-carb eaters
suffered from a 51% higher risk of dying from heart disease and a 35% higher
risk of dying from cancer.
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 cause drops in weight — but
that doesn’t make them healthy ways to do so.
There are currently no studies showing a ketogenic diet to
be beneficial to 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
After all, a whole foods, 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.