Have you heard all the buzz about the keto diet and want to know more? Did a friend tell you they’re “in ketosis” and you got interested? Here’s everything you need to know about ketogenic diets and being in ketosis for fat loss, brain function, satiety, and performance.
Editor’s Note: This article is being updated on an ongoing basis.
The only hard and fast rule of health is that health is personal and what works well for one person may not work for someone else.c
Aside from that rule, there are “frameworks” that seem to benefit large groups of people.
One more level down from that are alternative strategies that benefit smaller groups.
Ketosis is likely one of those alternative strategies that works well for certain, smaller groups of people. So, right off the bat I want you to understand that Ketosis might not be for everyone.
I’m going to lay out the case for potential benefits of Ketosis. If it sounds interesting and beneficial to you, then consider trying it.
What is the Keto Diet?
A ketogenic diet (“keto diet” for short) is a diet that puts you in a metabolic state of ketosis (more on that in a moment).
The diet is characterized by a specific macronutrient breakdown: high fat, moderate protein, and low carbohydrate.
Sometimes this macronutrient breakdown is confused with a traditional low carbohydrate diet, which is typically high protein, moderate fat, and low carb. Jillian Michaels recently made this mistake by suggesting that keto is simply a rebranded version of the Atkins Diet on her appearance on Steve Harvey, which I heavily ridiculed on my own podcast.
The reason the macro breakdown is important is because many people can’t achieve a state of ketosis when eating too much protein. This is because excess protein is converted to glucose in the body, which prevents (or pulls you out of) ketosis.
By shifting the macro breakdown toward fat as the primary macronutrient, you can keep protein low enough to achieve and maintain ketosis.
What is Ketosis?
Ketosis is a metabolic state that occurs when liver glycogen gets depleted and the body burns fatty acids for fuel.
The primary driver of this state is a very low carbohydrate intake. Often, it also requires a low protein, higher fat intake to match. Following a high fat, moderate protein, low carbohydrate diet (ketogenic diet) is what puts you in a state of ketosis.
You can also achieve a state of ketosis by not eating altogether (fasting).
When you’re in ketosis, the body produces something called ketones as a byproduct. Ketones are a source of fuel, just as glucose is a source of fuel.
Like glucose, ketones have a unique function and specific benefits tied to them and it’s these unique benefits that are highly sought after by keto dieters.
What can you eat on the keto diet?
I’ll talk more about this later, but if you want your ketogenic diet to be as healthy as possible, it needs to be based on you eating high-quality, real food.
What is real food? Basically anything that was previously alive. I have a real food cheat sheet that you can download, print, and stick on your fridge as a helpful resource for this.
Of course, not all real foods are going to work for keto – it’s about choosing foods that are going to help you hit a macro breakdown of about 60-70% fat, 30%-40% protein, and 5-10% carbohydrates (this ratio is different for everyone!).
Mostly what you need to avoid (if you’re using that cheat sheet) are starchy carbohydrates. When you keep carbs very low, then it’s just a matter of playing with your fat and protein ratio to see what your body needs to achieve and maintain ketosis.
Since you need to take in more fat than protein, it’s also unhelpful to choose lots of lean meats. If you’re going eat fish, eat fatty fish. If you’re going to eat a steak, choose a fatty cut of steak. Again, more on this later, but when you’re eating the fat of animals it’s highly imperative that you eat well-sourced animals (grass-fee beef, wild-caught fish, etc.)
Since fat is a store of toxins in animals, eating the fat of poorly raised animals is a step in the wrong direction for your health.
Most keto dieters add pure fat via other sources in order to make the macros work out. Some of their favorite sources are grass-fed butter, avocados, coconut oils, heavy cream, olive oil, cheese, MCT oil, and bulletproof coffee.
You can use keto test strips to measure your ketones (via your urine) to verify whether or not you’re in a state of ketosis.
What role does Ketosis play in human health?
Ketosis allows our bodies to function in the absence of carbohydrates, both physically and mentally. Instead of burning carbohydrates, or converting protein to glucose, the body burns ketones.
This is pretty much a survival mechanism. It allows your body to function in a state of caloric deprivation. This is why ketosis often gets bad press (as it’s linked to “starvation”).
Being a survival mechanism doesn’t make it invalid as a strategy, though. There can still be potential benefits to be had. Let’s cover a few of them…
The Keto Diet and Accelerated Fat Loss
Being in ketosis has a positive effect on hormone regulation. Namely, blood sugar regulation.
Think about someone who eats whole grains at every meal, throws down a Naked Juice, and caps dinner off with a Weight Watchers ice cream bar. What you’re seeing is a person who is on a blood sugar roller coaster.
These blood sugar spikes trigger both fat storage and future hunger. The fat storage is due to the hyper-caloric environment this type of eating tends to put people in. The insulin dysregulation causes constant hunger and cravings.
Now imagine a person who is avoiding carbohydrates, keeping protein to moderate levels, and getting adequate levels of fat. Assuming they’re eating quality foods, they’re getting all the micronutrients they need. Assuming they’re also eating enough calories, they’re not starving themselves. The diet is meeting their needs and their blood sugar is remaining very stable in the process.
Following this high fat, moderate protein, low carbohydrate model can induce ketosis. Your body’s main interest is to create the ketones it can use for fuel in the absence of glucose. In other words, your body’s main interest is to burn fat.
What’s interesting is that research shows that ketosis reduces body fat to a far better degree than restricting calories. In children, at least (but there are other studies that reflect the same findings in adults).
Now, I want to be very clear about this, because Keto is becoming a sort of religion – you do not need to be in ketosis to burn fat. You can reach all the health and fitness goals that you’ve set without going keto and there is a lot more to think about when it comes to losing body fat than your diet.
The Keto Diet: Disease Treatment, and Health
Besides turning on your fat burning furnace, dipping into ketosis may be beneficial for health and disease treatment. One of the most interesting areas of study has to do with ketosis and starving cancer cells.
Many cancers feeds on glucose, which leads to the obvious question, “What happens when you take away the glucose?” For normal cells, they switch to using ketones for fuel as we discussed earlier. But there are studies that show cancer does not have the ability to use ketones for fuel, thus they starve:
“Your normal cells have the metabolic flexibility to adapt from using glucose to using ketone bodies. But cancer cells lack this metabolic flexibility. So we can exploit that,” Dr. D’Agostino explained.
Another area where ketogenic diets are being heavily tested is in the treatment of Diabetes. Both Type I and Type II diabetics seem to respond very well to being in ketosis. Keep in mind this is separate from the condition of ketoacidosis, a dangerous condition for Type 1 diabetics.
There are dozens of studies targeting the treatment of a range of health issues using ketogenic diets. I can’t cover them all here, but I’ll give you three more: ketogenic diets have shown to be beneficial for those suffering from Alzheimer’s Disease, Parkinson’s Disease, and Epilepsy. This appears to be due to the neuroprotective nature of ketosis, it’s ability to slow or halt cellular death, and it’s positive effects on inflammation.
Improved Focus and Brain Function on the Keto Diet
At this point I could hit you with a string of confusing science terms. But, Rebooted Body is not about making you feel like you’re back in Biology class preparing for your final exam. And this is a “beginner’s guide” to ketosis. So, I’m going to water this down a little bit.
One of the mechanisms that causes so many brain issues – seizures, migraines, bipolar, ALS, dementia – is neurotoxicity. One cause of neurotoxicity is too much glucose. So, by reducing the glucose supply and asking the brain to burn ketones for fuel, a leveling out of sorts occurs.
There’s another byproduct of all this. Brain function. How clearly you focus, think, and recall information. Ketogenic diets improve brain function through the mechanism of clean fuel production. It appears that ketones are a more efficient and cleaner form of fuel for the brain than glucose.
To explain, we need to talk about mitochondria, the workhorses of your cells. ATP powers these mitochondria. ATP can be made from glucose or ketones. When ATP is made from glucose, free radicals are a byproduct. Free radicals are those pesky things that cause cellular damage and eventual disease.
ATP production from ketones is much cleaner, producing less of these free radicals.
What if your car’s engine was running on a mixture of gasoline and sugar? You wouldn’t be getting optimal function.
The Keto Diet and Satiety
I’ve said before that it’s possible to make the switch from being a “sugar burner” to a “fat burner.” That’s an oversimplified description, but I still don’t see anything wrong with it.
What we’re talking about here is how your metabolic state can shift to rely on glucose. This can happen through years or decades of ingesting far more glucose than your body needs.
So, what happens when you remove or reduce glucose intake from a person who is “sugar-adapted?” Well, they hate life for about three weeks because their cells are inefficient at using fat for fuel in the absence of glucose.
But, what happens after this period of time if you stick it out? You can become what’s called keto-adapted. This is where your body “switches” and becomes more efficient at using fat to run your body’s systems.
This doesn’t mean you should be in ketosis your entire life. What I’m saying is that your body should have the ability to use both ketones and glucose for fuel, seamlessly switching between the two.
As a sugar burner, you’ve got one source to choose from: glucose. When your metabolism is fully functional, you’ve got two sources to choose from.
Best of all, when your body doesn’t need glucose, you enjoy steadier energy levels. You’re not hunting for snacks and more food at all times. Your body isn’t threatening to pass out because you forgot to bring change for the vending machine.
Athletic Performance on the Keto Diet
The last aspect of ketosis is how it affects performance.
You might assume that ketosis sucks for performance because Gatorade has sent you an opposing message your entire life. They say that if you want to perform well, you need to ingest glucose-water.
And that may be true if you’re a helpless, sugar-adapted human. But what about those of us who have no trouble burning fat? Is it possible that I can be the all-star on my flag football or ultimate frisbee team if I start the day off with bacon and eggs? And if I hydrate with nothing more than good old-fashioned water?
Then there’s this video of Dr. Peter Attia doing demanding work in a state of ketosis and he looks like he’s handling it pretty well. There’s also this write up he did about low-carb and performance.
Is a keto diet actually healthy?
A lot of people argue about the healthfulness of a ketogenic diet and while I’m not going to make any claims about the long-term healthfulness of keto, I’ll make one thing clear: there’s a really easy way to make keto unhealthy…
If you want to make keto objectively unhealthy, consume lots of vegetable and seed oils for your fats and consume lots of really low quality, poorly sourced animal protein (like fatty steak from poorly treated, poorly fed animals).
You could also eat highly processed, “low carb” packaged foods full of bad fats and additives.
If you can commit to eating high quality fats, high quality protein, and maintain a solid variety of foods to make sure you’re not getting any nutrient deficiencies, you’re going to be much more well off.
It’s Not All Rainbows and Unicorns: 3 Reasons You Might Want to Ditch the Keto Diet
Okay I’ve spent a lot of time building up the “pros” of the Keto Diet, but it’s important to not get carried away. There are some real cons to the Keto Diet that you need to be aware of.
See, I’m not convinced that most people should be Keto. It’s been billed as a great way to lose weight, which has attracted a lot of attention, but it’s not all roses, unicorns, and fairy dust.
Here’s three reasons why you might want to reconsider your plan to go Keto…
1. The Keto Diet is obsessive.
Ketosis is notoriously difficult to get into, verify, and sustain without bringing back some of the old, obsessive Dieting strategies that we’ve been working so hard to get away from.
Tracking macros, monitoring blood glucose, and testing ketone levels are all required steps in the process for most people.
This kind of protocol attracts people with disordered eating habits. It’s the perfect blend of effective, obsessive, and new. It can also give someone disordered eating habits if they’re not careful.
Keto, after all is becoming somewhat of a religion and the zealotry is off the charts. I’m talking “Keto 4 life!” kinda stuff – it’s bad.
If you’re trying to get into ketosis for medical reasons, then you’ve gotta do what you’ve gotta do. If you want to get into ketosis because you heard it’s great for weight loss or for some other non-medical reason, it’s too obsessive for my taste.
2. The Keto Diet probably doesn’t fit your lifestyle.
You know me—I’m not a huge fan of cardio or long workouts. I’m bearish on exercise as a modern concept, but I’m bullish on functional fitness and DWYLT.
In order to actually enjoy those things and feel strong and healthy when doing them, you’ll need adequate glycogen. That’s something that’s quickly depleted through ketogenic eating.
I know the body can replenish glycogen stores through gluconeogenesis, but damn, why go through all the trouble?
Seriously, performing well on a ketogenic diet (I know this from experience) requires a long adaptation period and still results in the loss of explosiveness.
Endurance may be maintained or improved after adaptation, but good luck with those sprints, feeling strong popping up on a surfboard over and over again, covering your friend in a game of flag football, or lifting that sandbag many times.
And I still haven’t talked about the actual eating side of things: if you think it’s tough to get comfortable with social eating on a real-food based lifestyle, good luck with that keto plan. In the real world, most of the people I meet want less obsessiveness and more enjoyment, not vice versa.
Between the obsessiveness, performance issues, and social neediness, I’m getting further and further away from liking keto as a strategy.
3. The Keto Diet may have various negative long-term consequences.
There are a lot of little side effects considered to be “negative” on ketogenic diets. There are some small positives as well (such as increased mental clarity). I’m not going to hash out all the little things here. I want to hit on two of the top negative consequences.
Ketosis requires very low carbohydrate consumption. In my article, The Practical Truth About Carbohydrates, I noted that one of the potential downsides of this is a reduction in your metabolic rate.
The mechanism for this is chronic calorie restriction, which can easily happen on ketogenic protocols due to the satiating nature of fat and protein. In other words, it’s common for people on ketogenic diets to accidentally under-eat because ketosis does such a great job of turning off hunger.
This paradigm is especially destructive when sleep, stress, nutrient density, and inflammatory exercise are not considered. Doing ketosis properly requires having ALL of your ducks in a row.
Another consequence of ketosis is a potentially negative change in gut flora. The mechanism for this is a lack of fermentable substrate—the stuff your gut bugs feed on—as well as a change in the pH of the gut. You can read more about this, if you’re interested, at The Human Food Project.
The study of the gut biome is a relatively new science and is highly complicated. I’m not taking any hard-line stances on this right now, but you should note that if the science continues to trend in the direction it’s moving, it spells potential disaster for long-term, very low carbohydrate or ketogenic protocols (and those following ketogenic diets for medical reasons will need to look at strategic supplementation of fermentable fibers).
What’s the key takeaway?
The vast majority of people don’t need to be worried about getting into and staying-in ketosis. If anything, I recommend a cyclical keto diet, but certainly nothing long-term.
Many people who come to my community ask me questions about ketosis as if they believe it’s now the only path to weight loss. That’s scary. There’s a lot of brainwashing going on.
As I’ve said before, I’m all for experimentation. Unless you’re prone to disordered eating and Diet-jumping, try it out and see what your results are. But know that ketosis is not required and it could potentially be destructive.
If you’re going to ignore the possibility of these downsides and do keto anyway, or you just want to experiment but don’t want to trend toward destructiveness, you need to download our free Keto Diet Cheat Sheet…
Kevin Geary is the founder of RebootedBody.com and a respected expert on cravings, eating psychology, and long-term habit change. He’s helped tens of thousands of men and women in over 35 countries around the world through his online academy and now offers all of his signature programs through a “pay what you want” model.