6 Science-Backed Reasons You Shouldn’t Use the Keto Diet
Why the latest diet craze isn’t all it’s cracked up to be
The Ketogenic diet, first developed in the 1920s as a method of epilepsy management, has recently seen a surge in mainstream popularity largely due to the promises of:
- Creating faster fat loss
- Providing numerous health benefits
- And making you feel better than ever
However, despite its rise in popularity, it’s also one of the most polarising diets of the moment with fierce advocates and vocal detractors. (1)
What’s certain is that with the continual rise of social media and accessibility of information, more and more people are diving headfirst in the Ketogenic diet without really know what they’re getting into.
What Is The Ketogenic Diet?
The Ketogenic diet commonly referred to as keto, is a low-carb, high-fat and moderate protein diet.
It shares similarities with other low-carb diets like Atkins and involves drastically reducing total carbohydrate intake and substituting it with fat in order to create a metabolic state called ketosis.
Ketosis is when your body burns fat for energy in the absence of glucose from carbohydrate. It does this by converting fat to ketones in the liver which can then be used as energy by the body. (2)
To accomplish this, the standard ketogenic diet has you eating 75% of your daily calories from fat, 20% from protein and 5% from carbs.
Using this setup someone eating 2,000 calories would get no more than 100 calories from carbs per day.
This requires you to remove all traditional carb sources including bread, pasta, potatoes as well as most fruits and vegetables.
Still interested in going Keto? Here are 6 science-backed reasons you shouldn’t.
#1: Total Calorie Intake Is Still the Most Important Thing
When it comes to changing your weight it’s total calorie intake, not the type of diet you follow that matters the most.
This means that although the diet you follow is important for the way it impacts your health and your ability to create and sustain weight change over time, it’s the total number of calories you eat on a daily basis that will determine how your weight changes.
What you eat, when you eat it and how you eat it just don’t make a difference in the same way your total calorie intake does.
In particular, it’s the relationship between the number of calories you consume and the number of calories you burn for energy that you need to pay attention to.
It’s this relationship that will determine how your weight changes with 3 possible outcomes:
- Weight Loss: If the number of calories you consume is fewer than the number you burn for energy you will lose weight. The greater the difference the larger the effect
- Weight Maintenance: If the number of calories you consume is equal to the number you burn for energy you will maintain your weight
- Weight Gain: If the number of calories you consume is greater than the number you burn for energy you will gain weight. The greater the difference the larger the effect
You will always be in one of these states, which means your ability to maintain your desired state of energy balance is how you create lasting change in your weight over time.
It’s important to realise that the ketogenic diet is just one way of doing this and whilst it may be effective for some people it still only works in the way that all other diets do, by regulating your calorie intake.
#2: You Don’t Have to Go Low Carb to Lose Weight
Low carb being superior for weight loss is often the crux of the argument for a Ketogenic diet. However, it stems from a misunderstanding of carbs, weight gain and the role of insulin.
When you eat carbohydrates your insulin levels rise to prevent the release of stored energy (fat and carbs) so your body can prioritise the use and storage of the food you’ve just eaten. (3, 4)
The main argument for Keto advocates is that by severely restricting carbohydrate intake you won’t spike insulin levels and will spend more time burning fat instead of storing it.
A look at the evidence might appear to support this at first as it does show that low carb diets result in weight loss. (5, 6, 7, 8)
However, upon closer inspection and consideration of eating habits, it becomes clear that weight loss when following a low carb diet is actually the result of a reduction in total calorie intake and an increase in protein (which is very satiating), not its effect on insulin. (9, 10, 11)
Not to mention the fact that protein intake also causes a rise in insulin, which if the above theory of how the Ketogenic diet worked held true would see an increase in fat storage regardless of total carb intake.
In reality, in healthy individuals’ insulin will only spike in response to meals.
This means when you’re in a fed state i.e. after eating, your body will preferentially use and store that food than draw from your body fat stores or muscle glycogen for energy.
However, during periods of fasting, like overnight or extended times between meals, insulin will return to normal and you will burn stored nutrients for energy.
This means over a 24-hour period everything will balance out and if you’re in a calorie deficit you will lose weight.
All of this isn’t to say that you can’t lose weight on a low carb diet but more to show you that going low carb isn’t necessary to facilitate weight loss.
#3: Bulletproof Coffee Isn’t the Best Way to Start the Day
With the rise in popularity of the Ketogenic diet, an array of keto suitable foods and drinks has also sprung up.
Perhaps most widely spread is bulletproof coffee (BPC) which boasts the ability to prevent hunger, increase satiety and kickstart your ketosis.
BPC replaces your breakfast meal and consists of 2 cups of coffee, 2 tablespoons of grass-fed, unsalted butter and 1–2 tablespoons of MCT oil.
The problem is BPC has a few big downsides.
It’s Low in Nutrients
Firstly, its recommended that you drink BPC in place of your normal breakfast and whilst it’s clearly packed full of fats it’s lacking in all other areas.
This means if you normally eat 3 meals a day and replace one of them with BPC, you’re essentially cutting your nutrient intake by a third, which if not accounted for can have an adverse impact on your health over time.
It’s High in Calories
One of the big draws of BPC is the fact it supposedly helps you burn more fat, but when you consider than each cup is approximately 500 calories this looks a lot less likely.
To lose weight, ketogenic diet or not, you need to be in a calorie deficit and by starting your day with a 500 calorie drink you take a big chunk of calories off the table for no real benefit in return.
It’s High in Saturated Fats
On top of the above points, BPC is also high in saturated fats and whilst their effects can be controversial it’s commonly believed that high intake is associated with greater risk factors for many diseases. (12)
Consuming your daily allowance of saturated fats, or close to it, in one go may be putting you at risk of complications further down the line, particularly if the rest of your diet is not nutrient-rich and balanced.
#4: It Can Offer Fat Loss Benefits but Not in The Way You Think
A ketogenic diet is merely one way of creating and maintaining a calorie deficit over time.
The main way it does this is by severely restricting carbohydrate which in and of itself creates an instant reduction in total calories consumed. (13)
Does this mean it’s good for fat loss?
Well, it can be and there are several studies showing that a Ketogenic diet can result in weight loss and in turn improved health. (14, 15, 16)
However, it’s also worth pointing out that research, on the whole, shows that there is no statistical difference between weight loss on the Ketogenic diet and weight loss following a standard diet (that includes all macronutrients). (17, 18, 19, 20)
So, the question becomes, does the Ketogenic diet offer any benefits when it comes to creating and then sustaining a calorie deficit in order to lose weight?
Maybe, but probably not.
For example, there is research that shows that a low carb ketogenic diet that is high in protein can reduce hunger and overall food intake more than a high protein, moderate carb diet. (21)
However, it’s likely the reason for this is because both protein and fat both take longer to breakdown and digest which makes you feel fuller for longer after meals.
This can obviously be hugely beneficial when it comes to hunger management and calorie intake but is not necessarily game-changing.
All in all, the Ketogenic diet may offer some benefits when it comes to being able to create and maintain a calorie deficit but this is largely due to high levels of satiety after meals and not some special fat-burning property of the diet.
#5: Your Workouts Will Suffer (At Least in the Short-term)
What most people mean when they say their goal is fat loss, is the combination of fat loss and muscle retention.
This is because maintaining your muscle mass as you lose fat is what will result in that lean and toned look. A large factor in doing this is regularly lifting weights and building or at least maintaining strength.
The issue is a Ketogenic diet may, at least in the short-term, impair your ability to do this effectively.
This is because research (22) shows that glycogen stored in your muscles is the primary fuel source of moderate to intense exercise like weightlifting and by keeping your glycogen stores full can improve your performance in the weights room (23).
In other words, when you lift weights your body wants to use glycogen to fuel this activity. Which means having full glycogen stores in your muscles translates to a better workout. (24, 25)
The issue is when following a ketogenic diet, particularly in the first couple of weeks or months as you adapt, your glycogen stores will be empty which results in you feeling tired and sluggish when working out.
Whilst everyone will eventually adapt to working out in ketosis, it’s common for some people to notice an overall difference in workout quality when following a Keto diet.
How this might affect you is hard to say, but it’s worth bearing in mind that if your goal is related to changing your body composition then you may be better served by keeping carbs in your diet.
#6: It’s Not Superior for Muscle Growth
It’s not uncommon for superior muscle growth to be high on the list of reasons you should do the Ketogenic diet, but is it all it’s cracked up to be?
Researchers (26) looking to measure the effectiveness of a Ketogenic diet for muscle growth studied the effects of a 6-week diet on body composition in healthy, normal-weight men.
They split the men into 2 groups, one followed a Ketogenic diet and the others followed a regular diet. After six weeks, they found that those who followed a keto diet gained just over 2 lbs of muscle, whereas the regular diet group had only gained 1 lb.
Whilst this seems like a win for the Ketogenic diet, when you closer at the study you discover 2 major problems:
- Firstly, the keto diet group ate twice as much protein which in and of itself could account for the extra muscle growth
- Secondly, the 2 groups didn’t follow the same workout plan but instead were left to continue with whatever they were doing before joining the study. Again, this could account for the difference in total muscle mass gained.
In another more recent study, researchers again looked to study the difference in muscle growth between ketogenic dieters and regular dieters. (27) In this study they had all participants eat the same amount of protein and follow the same workout plan for 11-weeks.
In a case of déjà vu, at the end of the study, the Keto dieters were found to have gained about twice as much muscle as the regular diet group. However, again, when you look more closely there is a big problem with this.
In the final week of the study, the Keto dieters have carbs reintroduced into their diet which resulted in them gaining an average of 7 lbs.
This means the increase in muscle size came from the increase in glycogen and water stores in the muscles, making it a false positive.
This finding is supported by the fact that during the previous 10 weeks of the study both groups gained muscle at more or less the same rate.
So, where does this leave us?
Well, based on the available evidence a logical conclusion would be that there is not much difference in your ability to build muscle on a ‘regular’ diet compared to the ketogenic diet.
Which means the ketogenic diet offers no advantage for muscle growth, but nor is there any obvious disadvantage.
- A study (28) conducted in Brazil that looked at the difference in muscle growth* between a carb-restricted keto-type diet and a regular moderate carb diet in a group of overweight men and women found no statically relevant difference between the two.
*Both groups lifted weights 3 times a week for 8 weeks and ate a similar amount of protein which was approximately 0.7 g per lb of bodyweight.
This results in also seen in various other studies.
- A study (29) looking at gymnasts found that after 30 days following a ketogenic diet, participants lose fat but increased muscle mass.
- A study (30) looking at CrossFit training and showed no significant difference between keto and regular diet participants when it came to muscle mass and performance
This means if you combined a sufficient protein intake with consistently hitting your calorie intake and a suitable resistance training it is possible to both maintain and build muscle whilst following a ketogenic diet.
However, it is not a superior method of doing so and of course, results vary between individuals which means it’s impossible to say what your individual outcome will be; maybe you thrive, maybe you struggle.
The Bottom Line
The ketogenic diet is just one way of eating and whilst it can help some people lose weight or build muscle it’s not superior at doing either.
When it comes to picking the diet that’s right for you, it’s important to consider the bigger picture; is it good for your health, can you maintain this way of eating over time and can it help you reach your goals?
For most people, the Ketogenic diet will not be a sustainable way of doing this and should probably be avoided.
