- Myth #1: You Need Carbs to Thrive
- Myth #2: Keto Lacks Micronutrients
- Myth #3: Caloric Restriction is Healthier Than Keto
- Myth #4: Keto Advocates Unhealthy Fats
- Myth #5: Saturated Fat Causes Heart Disease
- Myth #6: Keto is Bad For Gut Bacteria
- Myth #7: Low-Carb Diets Can Kill You
- Myth #8: Low-Carb Always Means Keto
- Myth #9: Keto Impairs Exercise Performance
- Myth #10: You Can’t Build Muscle On Keto
- Myth #11: Eliminating Whole Grains Is Unhealthy
- Myth #12: Long-Term Keto Is Dangerous
You may have heard the rumors and keto myths…
Super low-carb, high-fat keto diets are terrible for you…
The keto diet deprives your body of essential nutrients…
Keto harms your gut bacteria…
It’s best to stick to caloric restriction and whole grains…
It makes sense. Nutrition is a heated subject. And it’s tough to get right in the lab. Controlling for outside variables in human nutrition studies — especially over the long-term — is difficult.
But when it comes to the ketogenic diet, there’s a lot of really good science. From blood sugar control to weight loss, to heart disease and Alzheimer’s prevention — not many diets can compete with keto in the lab[*][*][*][*].
The diet you choose is personal to you — from low-fat, to low-carbohydrate, to getting into a state of ketosis — you have to choose what’s right for your body.
But whether you choose keto or not, it’s time to bust some keto myths out of the water with the same studies that made the keto diet so popular to begin with.
The Truth About The Keto Diet: 12 Keto Myths Debunked
Myth #1: You Need Carbs to Thrive
Of the three macronutrients — carbohydrates, protein, and fat — only one, from a survival perspective, is optional.
So. Which one is it?
It’s not dietary fat. You need fat to form cell membranes, produce energy, and absorb fat-soluble vitamins like A, D, E, and K[*]. One such dietary fat — omega-3 fatty acid — is crucial for healthy cognition, and makes up a substantial portion of your brain’s weight[*].
It’s not dietary protein. You need protein (and its constituent amino acids) to build and repair every organ and tissue in your body — not just muscle tissue. Amino acids, and the genetic materials that direct them, are the basis for all life[*].
That leaves carbohydrates.
You might be wondering: without carbs, how can you maintain adequate blood sugar levels? Won’t low-carbohydrate diets cause hypoglycemia?
Your body is smarter than that. Early humans, often deprived of carbs for long stretches of time, evolved two glucose backup systems:
- Gluconeogenesis: how your liver creates glucose from compounds like lactate[*]
- Glycogenolysis: the breakdown of glycogen, your storage form of glucose
Glycogen cells in your muscle and liver tissue alone can hold about 500 grams of glucose[*]. That’s 13.5 potatoes!
And when glycogen gets low, gluconeogenesis can restore it again. Low-carb athletes tap into this system with much success[*].
Myth #2: Keto Lacks Micronutrients
Micronutrient deficiency is a problem, but not just for people on a keto diet.
There are plenty of folks who follow a low-fat, low-calorie diet or a standard American diet and suffer nutrient deficiencies.
If you do keto wrong, you may end up deficient in certain vitamins and minerals. That means not eating your non-starchy vegetables or relying on grain-fed cheeseburgers for every meal.
But do keto correctly, eat real, whole foods, and you shouldn’t have a problem.
The fact is: meat, vegetables, and healthy fats are the most nutrient-dense food groups on the planet. High-sugar fruits and grains pale in comparison.
Take magnesium, a nutrient sorely lacking in the standard American diet. Without adequate magnesium, muscles, nerves, and DNA suffer[*].
What foods are high in magnesium? Leafy greens, almonds, nuts, and seeds are just a few. All of those are allowed (and encouraged) on a healthy keto diet.
And for extra micronutrient insurance, you can always add a high-quality greens powder to your arsenal.
Myth #3: Caloric Restriction is Healthier Than Keto
Several studies in monkeys and mice have shown that caloric restriction (CR) — eating 10-50% less food over an extended period — translates to a longer lifespan[*].
Many have seized upon these findings without taking the time to understand the science, and its relevance to humans.
First of all, humans aren’t rhesus monkeys. What worked for them may not work for us.
Second, in most of these studies, the control group (non-CR rhesus monkeys) were allowed to eat as much sugary monkey food as they could stomach[*].
So, what researchers really found was that calorie-restricted monkeys lived longer than perpetual-buffet monkeys.
And when researchers at the NIA ran a similar study — this time modulating portions in the control group — the longevity effect of caloric restriction vanished[*].
Finally, CR has unwelcome side effects on both bone density and muscle mass[*].
The ketogenic diet does not have these side effects. Keto helps preserve muscle[*].
Myth #4: Keto Advocates Unhealthy Fats
There’s nuance to any diet, and the ketogenic diet is no exception. Simply eating low-carb and high-fat won’t cut it. The type of fat you eat matters.
Take vegetable oils. Soybean oil, safflower oil, sunflower oil, canola oil, and peanut oil are some of the unhealthiest processed foods on the planet.
Some reasons why:
- Vegetable oils are high in omega-6 linoleic acid, known to cause inflammation and obesity[*][[*]
- Cooking with vegetable oils generates oxidized lipids — particles that contribute to atherosclerosis (heart disease)[*]
- Merely breathing fumes from cooked vegetable oils causes DNA damage[*]
So yes, a high-vegetable oil diet increases disease risk, inflammation, and cellular damage. Sadly, some folks have lumped the entire low-carb community into this “dirty keto” zone.
But any responsible source of keto information will emphasize the right fats for a keto diet.
- Monounsaturated fats like olive oil, avocados, and palm oil
- Saturated fats like egg yolks, animal fat, and coconut oil
Myth #5: Saturated Fat Causes Heart Disease
Most keto diets are rich in saturated fats like butter, animal fat, and coconut oil. The American Heart Association wants you to limit these fats, and replace them with vegetable oils[*].
The genesis of this advice is rooted in the 1950s. It was 1955, in fact, when Dr. Ancel Keys said that dietary saturated fat causes cardiovascular disease (CVD)[*].
Keys used worldwide population data to support his hypothesis. Certain populations ate more saturated fat and had more CVD. Others, like Italians, showed the opposite trend.
But, as the scientific mantra goes, correlation does not prove causation. Maybe Italians got more sun and omega-3s, or maybe they’re less stressed — and one of those things explains their good heart health.
The truth is: the time for speculation on saturated fat and heart disease has long passed.
Consider the following:
- Two recent meta-analyses (a meta-analysis combines and analyzes all available data) found no link between dietary saturated fat and heart disease[*][*]
- In a large Japanese sample, saturated fat intake was inversely associated with stroke[*]
- Compared to polyunsaturated fat (from vegetable oils), saturated fat is heat stable and doesn’t oxidize when you cook with it[*]
Myth #6: Keto is Bad For Gut Bacteria
Your gut bacteria need fiber to produce anti-inflammatory chemicals, boost mood, and support your immune system[*].
Since keto is low in starchy carbs (a major source of dietary fiber), many wonder if this negatively impacts your gut microbiome — starving the trillions of bacteria residing in your gut.
This is a valid concern, but it’s nothing to lose sleep over.
First, a low-carb ketogenic diet doesn’t have to be a low-fiber diet. The concept of net carbs is relevant here:
- Net carbs: The carbs that “count” on keto — equals total carbs minus total fiber. An avocado, for instance, contains about 11 grams carbs and 9 grams fiber. That’s only 2 grams net carbs, making avocados high-fiber AND ketogenic.
The same holds true for broccoli, asparagus, artichokes, and a host of other fibrous, non-starchy veggies.
There’s another reason keto may help your gut microbiome, not harm it.
In those with chronic stomach issues, high-carb, high-fiber diets may do more harm than good. The reason involves bacteria.
In his 2018 book Healthy Gut, Healthy You, Dr. Michael Ruscio recommends a low-carb diet for treating small intestinal bacterial overgrowth (SIBO), a condition at the heart of many chronic gut diseases.
Ruscio explains that the risk for SIBO derives, in part, from genetics:
“A carb and prebiotic-rich diet works for Africans,” writes Ruscio, “but if you are a Westerner, and especially if you are a Westerner with some gut issues, a high-carb and prebiotic diet might be the exact opposite of what you need. It may feed bacteria that your immune system is attacking.”
Myth #7: Low-Carb Diets Can Kill You
In August 2018, the British journal The Lancet published a controversial paper. Researchers had tracked 15,248 middle-aged adults over 25 years. The lowest-carb group, they found, also had the shortest life span[*].
The paper provoked waves of speculation about low-carb and keto diets. And a lot of fear-mongering.
Briefly, here’s why The Lancet data shouldn’t worry you:
- The data was correlational (which doesn’t prove causation)
- The low-carb cohort wasn’t keto, or even low-carb (40% calories from carbs is not keto)
- It was an observational study. In this uncontrolled framework, low-carb dieters were more likely to:
- Be men (men don’t live as long as women)
- Be smokers
- Eat fewer veggies
- Be sedentary
- Be overweight and diabetic
- The researchers didn’t account for alcohol intake, usually higher for people who consumed fewer carbs; when you drink a lot, you naturally eat less[*]
So based on this study: you might reasonably conclude that a diabetic sedentary smoker eating 35% calories from carbs won’t outlive his peers.
But you can’t say that low-carb diets kill you.
Myth #8: Low-Carb Always Means Keto
By calories, the ketogenic diet is usually 60% fat, 30% protein, and 10% carbs[*]. You can give or take a bit on protein and fat, provided your carbs stay low.
Low-carb diets don’t always meet these specs. Many low-carbohydrate diets are also low in fat, or chronically restrict calories — not sustainable for the long-term.
Similar logic applies to high-fat diets. They’re usually not keto either.
Consider research on mice fed “high-fat” diets. These mice develop insulin resistance, diabetes, and liver disease[*]. Then the media blames fat for these diseases in humans.
So next time someone questions a low-carb or high-fat diet, be sure to read the fine print. They’re probably not talking about a healthy keto diet.
Myth #9: Keto Impairs Exercise Performance
Popular wisdom says you need carbs to fuel glucose-related demands of exercise. You must “carb up” to refuel.
This claim is partially true. Hardcore athletes may benefit from targeted carb feedings here and there. This includes those doing martial arts, sprints, and Crossfit on a frequent basis.
But unless you’re going hard every day, your glycogen stores are probably deep enough to handle your regimen. Keep in mind: going keto can spare muscle glycogen, helping you go harder for longer[*].
Keto has been used for boosting exercise performance for some time. In 1983, Steve Phinney showed that cyclists — after six weeks of fat-adapting — performed better on their bikes[*].
So while performance may temporarily drop while you adapt to fat and withdraw from carbs — you shouldn’t let this deter you.
Myth #10: You Can’t Build Muscle On Keto
Visit any bodybuilding forum and you’ll find someone claiming you need carbs to build muscle. Carbs boost insulin, they’ll say, and you need insulin to grow.
But here’s the truth: a low-insulin ketogenic state is not only good for disease prevention — it’s also good for muscle growth.
For adding muscle, keto diets work better than high-carb western diets[*].
The mechanism is interesting. When you combine the ketone body beta hydroxybutyrate (BHB) with the amino acid leucine (from protein) — you preserve and synthesize muscle[*].
Myth #11: Eliminating Whole Grains is Unhealthy
The American obesity problem, dubbed “diabesity,” has grown to epidemic proportions. In the U.S. alone, obesity rates exceed 30% in more than 30 states[*]. Many are diabetic.
To treat type 2 diabetes — a condition marked by high blood sugar, high blood pressure, high insulin levels, and obesity — the American Diabetes Association (ADA) recommends a diet rich in whole grains[*].
Unfortunately, since this metabolic disorder is caused by high-carb, high-sugar diets, this recommendation is isn’t helping[*]. Meanwhile, rates of obesity continue to rise.
The real fix for type 2 diabetes? A low-carb ketogenic diet.
In one 24-week controlled trial, 84 diabetics were randomized to eat one of two diets: low glycemic (with whole grains) or low-carb ketogenic.
The keto group lost more weight and maintained lower blood sugar than the whole grains group. Many of the keto dieters were even able to drop their diabetes meds[*].
But wait. Don’t whole grains provide high levels of fiber and nutrients?
They provide some, yes — but vegetables are far more nutrient-dense. Plus, whole grains contain harmful compounds — phytates, lectins, and proteins like gluten — known to inhibit nutrient absorption and cause intestinal issues[*].
Myth #12: Long-Term Keto Is Dangerous
That said, there isn’t much long-term data on the keto diet.
But there is a bit of epidemiology. The Canadian and Greenland Inuit, for instance, have a long history of eating high-fat, low-carbohydrate diets of whale and seal. Almost no carbs. The Inuit were keto before keto was even a thing.
“Such a diet would have led the populations to be in a permanent state of ketosis,” remark the authors of a 2014 paper in the American Journal of Human Genetics[*].
Although the Inuit likely possess superior fat-processing genes, their example does suggest that permanent ketosis is sustainable on a large scale.
But the more reliable data must come from you, from your own keto experiment.
Give keto a couple months. See how you feel, monitor your blood work. If everything looks good — if your health is improving — stick with it.
Bottom line: There isn’t much data on long-term ketosis, but there isn’t any data that suggests ketosis isn’t sustainable, either.
The Truth About Keto
Everyone, of course, is entitled to their opinions. But when making important health decisions, it’s crucial to leave opinions aside and turn to data as much as possible.
This isn’t to say that keto is the only healthy diet. If you fare better on another diet, stay with that diet.
The important thing is to listen to your body, track your progress, and monitor your lab work.
Finally, take everything you read with a healthy dollop of skepticism. No matter how famous the source.