We spend our days reading this and other health blogs, communing with Primal and keto folks on social media, staying abreast of the nutrition literature, arguing about arcane metabolic minutiae on forums, counting your linoleic acid intake, and you forget that most people don’t know 2% of what you know about diet.
So, when you hear people criticize keto, don’t get exasperated (even if the criticisms are silly). Be ready to respond. And hey, not all criticisms are unfounded. In many cases, wrangling with them will only make you more honest and informed about your diet. Let’s look at some of the more astute keto critiques….
1) Your Brain Needs Glucose, How Do You Even Think?
This isn’t so much wrong as incomplete. Yes, the brain famously needs glucose—but not as much as we’re lead to believe. Once you’re keto-adapted, ketones can provide most of the brain’s energy needs. At max ketone production and adaptation, you’ll still need about 30 grams of glucose for your brain.
Your liver can make about 150 grams of carbohydrates a day from gluconeogenesis, so even if you don’t eat any carbs at all (and you can definitely eat carbs on keto) you’ll still be able to manufacture the requisite 30 grams of glucose.
The beauty of keto (and low-carb eating in general) is that it leads to low insulin—both fasting and post-prandial (after meals). When your insulin is low, you’re able to access your stored body fat and liberate it to be burned for energy. Since even the leanest among us carry pounds of body fat, that means you have tens of thousands of calories of clean-burning energy available for liberation at any time.
Once you’re keto-adapted, you’ll most likely find that you have steadier energy than before.
3) How Do You Get Fiber?
Actually, there are plenty of ways to obtain fiber on a ketogenic diet. Many of the best sources of prebiotic fiber—the kind that feed and nourish the good gut bacteria living in your digestive tract—are fairly low in digestible carbohydrates and mesh well with keto. For example:
Green bananas (Yes, a green banana is mostly resistant starch, which your body cannot digest.)
Almonds and pistachios
Plenty of fiber in those.
4) How Do You Exercise Without Carbs?
There are two primary energy systems used during exercise: aerobic and anaerobic. Aerobic energy relies on fat; anaerobic relies on glucose. The better you are at burning fat, the more work you can do while remaining aerobic. This preserves stored glucose (glycogen) for more intense efforts, increasing your overall energy efficiency. Particularly for endurance training, being keto-adapted allows you to utilize greater amounts of stored body fat for energy and reserve glycogen for when you really need it.
And besides, if you do engage in glycolytic, glucose-intensive training, you can always cycle carbs in and around your workout sessions. Your insulin-sensitive muscles will suck up any glucose you consume as glycogen without affecting your insulin levels or your ability to generate ketones and burn fat.
5) Doesn’t All That Fat Give You Heart Disease?
The vast majority of studies placing people on low-carb, high-fat or ketogenic diets find that markers of heart health improve rather than decline.
In obese adults with type 2 diabetes, a ketogenic diet improved blood lipids and boosted fat loss compared to a low-calorie diet.
In lean, healthy adults without any weight to lose (and who didn’t lose any weight during the course of the diet), total cholesterol went up from 159 to 208 mg/dL and triglycerides fell from 107 to 79 mg/dL. A lipophobic doc might freak out at the rise in TC, but given that the triglycerides dropped, I bet the change reflects a rise in HDL and an overall positive, at worst-neutral effect.
Now, do some people see classically-deleterious changes to their blood lipids? Sure. Anything can happen. We’re all different. I talk more about keto and cholesterol effects here. But the weight of evidence shows that becoming fat-adapted through a keto diet is better for your heart health than not.
6) You’re Just Losing Water Weight, Not Fat
Here’s the truth:
Yes, when you go keto and start shedding glycogen from your liver and your muscles, you lose a lot of water. That’s because every gram of glycogen is stored with 3-4 grams of water. Burn the glycogen and you lose the water along with it.
But this glycogen-and-water loss is a prerequisite for losing “real” weight. It’s a harbinger for fat loss. Once the glycogen runs low, that’s when you start getting into deep ketosis and developing the ability to burn massive amounts of body fat for energy.
7) I Heard the Keto Diet Kills Your Gut Bacteria
Ah, yes, I remember that study. They either fed people a varied diet of fruits, vegetables, grains, legumes, and other foods—or a diet of lunch meat and cheese. Turns out the lunch meat and cheese “keto diet” was bad for the gut biome, increasing gut bacteria linked to obesity and metabolic problems and decreasing gut bacteria linked to health. Of course it was.
A keto diet doesn’t have to consist of bologna and American cheese slices. In fact, it shouldn’t. As I explained in the fiber section, a well-formulated ketogenic diet is full of prebiotic fiber, non-starchy vegetables, and even low-sugar fruit that provide plenty of nourishment for your healthy gut bacteria. What these studies and media stories attack is a caricature of keto, a diet full of processed meat and low quality cheese. They aren’t relevant for someone following a Primal keto diet.
8) Keto Isn’t Sustainable
Well, what do you mean by sustainable?
If you’re talking about the “restrictiveness” of the diet at a personal level, that depends. Sure, you can’t go keto and continue eating Pop Tarts and donuts for breakfast, heaping bowls of pasta for lunch, and fast food burgers (with the bun, at least) and fries with a shake for dinner. But you can eat eggs, bacon, and blackberries for breakfast. You can eat a Big Ass Salad full of a dozen different species of vegetables for lunch. And you can have a ribeye with buttered broccoli for dinner with a glass of wine. I don’t know about you, but that’s a pretty damn sustainable way to eat in my book.
If you’re talking about the environment, and worrying about farting cows or whatever, the evidence is quickly accumulating that properly-raised and managed grazing livestock can sequester more carbon than they emit, revitalize (and even de-desertify) grasslands, and produce more calories-per-unit-of-input than conventional pasture-raising. A large portion of the world’s surface isn’t even suitable for growing crops and is better used for grazing animals. The environmental sustainability of meat-eating is still an open question, but the popular conception of “meat bad, grains good” is completely incorrect and incomplete.
What other keto criticisms have you encountered in the wild? Leave them down below, and thanks for stopping in today, everyone.
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.