by Christian Thibaudeau
Few topics are as polarizing as ketogenic diets, and there doesn't seem to be a middle ground. People either believe keto is the one and only correct way to eat, or that it's a dangerous fad, no better than any other diet that creates a caloric deficit.
Zealots will say there's a huge metabolic advantage. They'll tell you how it programs the body to use fat as your primary fuel source. They say it's more than just a caloric deficit. They talk about the great enhancements in mood, energy, cognition, and their capacity to deal with stress. Some say it gives them the ability to see unicorns and ride them around on rainbows made of kittens. (I'm exaggerating, but just a little.)
Those against it will argue that it's much harder to build muscle on a keto diet, that high intensity performance can drop, that cortisol will increase, that it becomes hard to sustain over the long run, and that recent studies report similar fat loss regardless of the carbs/fat ratio (if protein and calories are equivalent).
Who's right? And is there a middle ground?
Keto (ketosis) refers to a dietary approach that mimics the effect of fasting by minimizing insulin release. It does this by pretty much cutting out carbohydrates from your diet so that the body will start to produce ketone bodies which can be used efficiently as fuel by the muscles and brain. Once your body begins to use these for fuel, you're said to be in ketosis.
We're talking about a diet made primarily of fat, with clinical ketogenic dieters having as much as 80-90% of their caloric intake coming from fat. The version typically used by lifters would have a bit more protein – something like 65-70% fat and 30% protein.
The goal is to reach what's called "keto adaptation," a state where your body produces a lot of ketone bodies from fatty acids which become your primary fuel source. Keto adaptation normally requires a few weeks. Prior to reaching that state it's possible to have a drop in energy, mood swings, and problems concentrating. But, once adapted, these should level out.
The primary mistake I see is what I call the "bacon phenomenon." Some people go on a keto diet and see it as an all-you-can-eat bacon, cheese, cream, and butter fest. In theory that's fine because it upholds the keto ratios. But the kinds of fat present in these foods aren't exactly "health promoting" when overemphasized.
For example, I recently did a keto experiment and foolishly started with a high amount of the foods mentioned above. Within three days my blood pressure shot up from 115/80 to 155/110! Not exactly healthy.
But once I changed my food intake and types of fat (fish oil, olive oil, salmon, avocado, etc.) my blood pressure went down and actually reached a lower level than when I started at 111/77.
First Lesson: Even on keto, food choices matter.
Another common error, especially among lifters, is eating too much protein while trying to do a "keto" diet. In this case, it's a mistake. See, protein can be turned into glucose by the liver (gluconeogenesis). If you ingest too much, you'll simply use that protein for fuel by turning it into glucose, and keto adaptation will be a lot harder.
Second Lesson: To actually be on a keto diet, you have to use the correct nutrient ratio. Protein can't be higher than 25-30% of your caloric intake.
Keto dieting seems to blunt hunger once you're adapted, so while you have the illusion of "eating as much as you want and not getting fat" in reality you're simply satiated with less food, thus ingesting fewer calories.
And while there might be a slight metabolic advantage to keto dieting, allowing you to eat a bit more calories without gaining fat, it's not significant enough to say that calories don't matter and that you can eat all you want. Consume a significant caloric surplus on a keto diet and you'll gain fat.
Third Lesson: You still need to match caloric intake to your goals.
The final mistake is using a cyclical "ketogenic" approach in which you eat with a keto ratio for 5-6 days a week, then have a pretty large carb intake on the other day(s) to replenish muscle glycogen.
Good examples of this approach include Dan Duchaine's Body Opus and Mauro DiPasquale's Anabolic Diet. I'm not saying these approaches don't work. They can. But they're not truly ketogenic diets. Being in ketosis is very hard to maintain on this approach.
A large carb-up or cheat meal could decrease ketone production for 2-3 days (3-4 if you count the high-carb day itself) so you essentially spend each week trying to re-establish keto adaptation the first three days after the carb-up because on these three days you heavily rely on stored glycogen for fuel.
Then you'll have the three days where you use more ketones for fuel and you carb-up on the last day. The issue? Even though it works just as well for fat loss, you feel like crap and will have huge carb cravings most of the time.
Fourth lesson: A true keto diet means changing your way of eating all the time, not just a few days a week.
Here are some of the most common benefits that are associated with keto:
A lot of people love this approach because once they're in ketosis, they feel better mentally – calmer, more focused, less anxious. And it's true, I've felt it myself. So it does happen, at least in some people. Some believe it's because ketones give the brain seemingly unlimited energy, but that's not it. Or at least that's not the main story. There are three main reasons why keto can have a positive impact on cognition:
GABA, along with serotonin, is one of the neurotransmitters responsible for "neural inhibition." It calms the nervous system when it's over activated/excited. Anxiety is nothing more than your neurons firing too fast and you start overthinking, even to the point of paranoia. You experience tension and are prone to worrying.
People with low levels of GABA and/or serotonin have a harder time calming their neurons down. As a result, they're in a more anxious state and are more prone to panic attacks. Increasing GABA would help the brain deal with stressful event/situations.
It's been theorized that what we typically call "CNS fatigue" could in fact be a symptom of brain tissue inflammation. This would lead to a loss of motivation, drive, discipline, mood, and mental functions.
The brain does have insulin receptors. In fact, evidence points to brain insulin resistance as a potential cause for Alzheimer's disease (some even call it type-3 diabetes). Fixing that issue would have a significant impact on brain function and mood.
One reason keto works well is that it increases satiety; it blunts hunger more efficiently than other diets. If you're not a calorie-counter, you'll likely eat fewer calories on a keto diet. This might be one of the reasons why people seem to lose fat more easily when they go keto: they're consuming fewer overall calories.
And despite the trend among coaches to claim otherwise, caloric balance is the most important factor in losing fat. Other factors play a role, but calories in vs. calories out (especially with an equated protein intake) is the most influential one.
Still, having fewer cravings throughout the day and feeling more satiated is a benefit. It makes it easier to stick to the plan. Last time I did a keto diet I had zero sugar cravings, which is really unusual for me.
An increase in AMPK and a decrease in mTor have been reported by those using a ketogenic diet. This could potentially lead to an increased lifespan. However, the question remains: Is the increase in AMPK and decrease in mTor due to the specific macro breakdown or the caloric restriction that occurs? It's probably a combination of both.
The biggest claim of keto proponents is that it gives you a "metabolic advantage" that leads to greater fat loss than simply a caloric deficit. They say that if you eat 2000 calories on a keto diet, you will lose more fat than if you consume 2000 calories on a diet with higher carbs and lower fats. I don't see anything that allows me to comment either way, so I haven't included this claim as a benefit.
Gaining muscle mass might be harder than with a more common bodybuilding-style diet. The main reason is a systemic decrease in the hormone IGF-1 and insulin levels.
IGF-1 is likely the most anabolic hormone in the body and insulin also has an important role in muscle growth. Keto will decrease both and it's bound to have an impact on muscle growth. I'm not saying it's impossible to build muscle on keto, but it's a lot more difficult and slower than it would be if carbs are properly used in the diet, especially if you're a natural lifter.
For some, keto will also raise cortisol to a greater degree than diets that include carbs. One of cortisol's main functions is to maintain stable blood sugar levels; specifically, it increases it when it falls too much. Other hormones like glucagon and growth hormone are also used to increase blood sugar levels, so not everybody will get a huge jump in cortisol production during a keto diet. Some will get more of a growth hormone release.
Normally those who tend to overproduce cortisol – those who are naturally more anxious, stressed, and are more introverted – will overproduce cortisol. Of course, increasing cortisol too much can greatly slow down muscle growth or speed up muscle loss by increasing muscle breakdown, but also by increasing the expression of the myostatin gene, the gene that limits muscle growth.
This further explains why some people report decent muscle gain when keto dieting while others just can't add muscle, no matter what they do.
A last element to consider: keto dieting decreases mTor activation. mTor has a huge impact on protein synthesis/muscle-building and decreasing it could easily have a negative impact on muscle growth.
Note: People taking steroids and other drugs can "bypass" these issues and build muscle just fine on a keto diet. You have to keep that in mind when reading comments about it.
Here the data is equivocal: recent studies show that low-carb dieting does not lead to faster fat loss than low-fat dieting if calorie and protein intake are the same. But you'll also find several studies showing the opposite. Opponents of low-carb diets are quick to point out the studies showing no difference but forget the large body of work showing an advantage of low-carb over low-fat dieting.
I do believe that if we look at a large population, and not at individuals, the average fat loss should pretty much be the same whether you use a keto or carb-dominant approach, if protein and calories are equal. That said, some people might do better (for fat loss) on a keto diet while others will do better on a diet that provides more carbs.
Once again we have studies pointing in both directions. But if we look at real life, working out intensely is negatively affected when going on a ketogenic diet. This is especially true if volume is fairly high and the work is done often within 30-50 seconds per set.
Once you're fully keto adapted, endurance work won't be affected. A keto diet could even improve endurance performance by providing you with more easily accessible fuel.
But typical hypertrophy work will be affected. Of course there are lots of keto advocates who will claim that this isn't the case and that their own workouts aren't affected. It has simply not been my experience or the experience reported by many of my clients.
Physiologically speaking, ketones are not as effective as glucose to provide fuel for very intense muscle contractions. And while the average Joe who doesn't train that hard might not notice it, for someone who knows what it means to work hard, it can make a difference.
As for pure strength training, in theory it shouldn't be negatively affected because during the session you use mostly ATP-CP for sets of 1-5 reps. You don't need glucose/ketones that much so performance shouldn't drop much, if any.
However, when we understand that the brain and nervous system work best on carbs (ketones being a close second), there might be a performance drop in some individuals. But the main drawback of keto dieting when training heavy is that your CNS won't recover as fast after a heavy workout.
Your nervous system either gets excited or inhibited. You either amp it up or calm it down. When you're lifting you excite your neurons. This is what I called "activation" in the past: you wake up the nervous system by increasing the firing of your neurons.
The more force you have to produce, the greater the excitation/activation. After the workout, this neural excitation remains, and it's the role of serotonin (a neurotransmitter) to calm it down. But the longer it takes your nervous system to calm down, the harder it is to recover. As long as your nervous system is overly excited, you're fatiguing the CNS.
The quicker you can calm your neurons down, the faster you recover from a heavy session. Low-carb eating is associated with a decrease in serotonin levels. In that regard, people who already have lower serotonin levels (more anxious, low energy, hard time relaxing, overthinking, being lethargic, etc.) might find it extremely hard to recover from heavy workouts when they go on a keto diet.
I noticed that when I go on a keto diet my motivation to train goes down and I'm resistant to heavy lifting... instinctively. If you can't train as hard, or if your recovery is impaired, it might have a significant impact on progress.
Another element to consider is that keto dieting, like any other form of low-carb eating, decreases water retention. That can be considered either good or bad. Good in that it makes you look leaner than you are because you're holding less subcutaneous water. Bad because it can easily make you dehydrated. And even if you're not dehydrated, less water retention also means less strength. So depending on your goal, keto might not be a great option.
On a keto diet I lose a lot of muscle fullness. I look a lot smaller. It's logical though – if you're not eating any carbs your glycogen stores will decrease drastically.
With each gram of glucose stored in your muscles you also store 3 grams of water. If a well-built man can store 500 grams of glucose in his muscles, then depleting muscle glycogen could mean looking like you lost 2 kg (close to 5 pounds) of muscle. Because even though you lost water and glucose, they were stored inside the muscles, making them look bigger.
So while we're not technically losing muscle, we'll still look like we have less, which can have a negative impact on motivation.
By extension, this decrease in muscle glycogen can also make it a lot harder to get a good pump in the gym. I even noticed a decrease in mind-muscle connection: it becomes harder to "feel" the muscles contracting, which was really annoying for me.
I'll play devil's advocate and mention that on a keto diet you'll eventually increase intramuscular fatty acid storage, which can have a positive impact on fullness, but can't completely compensate for the glycogen depletion. In Quebec, low-carb dieting among coaches is still popular (probably one of the last places on earth where some bodybuilders use low-carb diets). We see a common denominator – physiques that look hard, but are super flat.
Although the pump itself shouldn't be a training goal, for many people not getting one can make the workouts less enjoyable and kill motivation. Even if keto was just as good physiologically for building muscle and exercise performance (which it isn't) that psychological factor could be enough for some to get worse gains.
While some people are going keto-for-life, others will get bored on it. Support groups can keep some of these people motivated for a time, but it's a band-aid.
And if you enjoy fruit, rice, pasta, potatoes, oatmeal and the occasional cheat, it will be impossible to stick to a keto diet for the rest of your life. Sure, you can have a treat here and there without getting off the keto bandwagon, but in reality this just delays the inevitable.
And it's not a discipline issue; you could have tons of discipline. You may be able to follow crazy, restrictive diets to reach specific goals. But can you really see yourself going keto for life? From my experience, any diet that completely discards one macronutrient is rarely sustainable.
The evidence regarding health benefits is fairly solid, provided that you make good food choices and don't turn it into a cheese-butter-bacon fest. And for fat loss it can work really well for many people, especially those who aren't under a lot of stress and not doing a physical job.
But if your goal is to gain muscle or get stronger it's not the best approach for you. Muscle gain will slow for a natural individual and it might become harder to recover from heavy, high-effort workouts. It might even affect strength negatively by decreasing water retention.
But if it fits your psychological profile, go ahead! If you're wanting to quickly look a lot leaner (photo shoot, vacation, big event) it could be useful because it will decrease water retention, giving the illusion of leanness.
It's not as good as its biggest proponents (who are usually selling something) are claiming. But it's not as bad as its opponents make it out to be. Like almost everything related to diet, it falls somewhere in the middle depending on what your needs are.