Many people believe that the keto diet is the fastest, most effective approach for weight loss. But is that really true? Let’s have the keto diet explained in an evidence-based way so you can decide for yourself.
“Bread? Gross, no, thank you – I’m on the keto diet.” Sit at any dining table these days, and there’s bound to be someone who conveys their disgust with carbs.
And given the explosive popularity of the keto diet in recent years, that’s unsurprising. Some have even added intermittent fasting to their keto diet in a bid to speed up weight loss.
So, what does this high-fat, low-carb diet have to offer that others don’t?
Can it help you lose weight faster? Is it a form of bio-hacking that gives you enhanced mental clarity? And might it be (cue gasp) the cure for cancer?
Let’s take a closer, evidence-based look at the keto diet.
What is the keto diet?
More popularly known as the ‘keto diet’, the ketogenic diet is often thought of as nothing more than a low-carb and high-fat diet.
But what they don’t realize is that the definition of the diet extends beyond shunning carbs and embracing fats.
Instead, the ultimate goal of the keto diet is to get the body to start relying (primarily) on fat for energy (1, 2, 3, 4).
And in general, that’s something our bodies doesn’t typically do; we’re predominantly fueled by glucose – also known as blood sugar, which we get from carb-rich foods (bread, cereal, pasta, rice, etc.)
How the keto diet works
But when the body is deprived of carbohydrates, it’s forced to find other ways to make energy for sustenance (thankfully), and one way is a process called ketogenesis (5, 6).
During ketogenesis, your liver breaks fat down into ketones: a usable energy source. And when you begin to produce a lot of ketones, your body enters the metabolic state called ‘ketosis,’ where you’re primarily getting fuel by burning stored fat (7).
More specifically, you’ve only ‘gone keto’ when your blood ketone levels measure above 0.5 mmol/L (8, 9, 10). And that means there’s no way you’d know that you’re in ketosis for sure unless you went for a blood test (11, 12, 13).
That said, though, the general guideline to successfully achieving ketosis is to limit your carb intake to less than 50 grams a day (14). Just for reference: a bagel has about 55 grams of carbs.
Ultimately, any diet that gets your body into ketosis is called a ketogenic diet.
- The ultimate goal of a ketogenic diet is to get your body into ketosis, where you’re now burning fat, instead of glucose, for energy.
- To successfully achieve ketosis, you generally need to limit your carb intake to less than 50 grams a day.
- You’re only considered to have ‘gone keto’ when your blood ketone levels measure above 0.5 mmol/L.
Types of keto diet
Accordingly, there are several versions of the ketogenic diet, including:
- Standard ketogenic diet (SKD): A very low-carb, moderate-protein, and high-fat diet; it typically contains 75% fat, 20% protein, and 5% carbs (15).
- Cyclical ketogenic diet (CKD): This variant involves periods of higher-carb refeeds, such as five ketogenic days followed by two high-carb days.
- Targeted ketogenic diet (TKD): A ketogenic diet that allows you to plan your carb intake around your workouts.
- High-protein ketogenic diet: Similar to the standard ketogenic diet, but with a higher intake of protein, the macronutrient ratio is often 60% fat, 35% protein, and 5% carb.
Do note that most of the available research involves the standard and high-protein ketogenic diets (with the SKD being the most researched). As of now, cyclical and targeted ketogenic diets have yet to be studied extensively.
Keto diet explained: is it better than other diets?
Of the many useful weight loss tips you read about, it’s often suggested that the keto diet helps you lose weight more so than other diets and that happens with good reason.
Those who switch to the keto diet do indeed experience significant weight loss. And incredibly quickly, too. In fact, research suggests that you could potentially drop up to 3 kilograms in your first week on a keto diet (16)!
But all that extra weight you lose is not body fat (17, 18, 19).
Instead, this loss is likely attributed to water weight. That’s because carbohydrate stores in the body’s muscle glycogen carry water molecules with them (20).
Unfortunately, that means that the numbers on the scale would bounce back once you replenish fluids!
Not to mention, there’s only so much water you can lose from your body. That’s why weight loss would inevitably slow with time when you’re on the keto diet.
As far as the keto diet’s track record with longer-term weight loss, research findings have been clear. When total calories and protein intake are equated, no particular diet – be it low-carb or low-fat – stands out as a winner (21, 22, 23).
Remember: in the end, fat loss is all about how many calories you eat (24, 25, 26, 27).
If you eat fewer calories than you expend, your body will be forced to burn off its excess fats for fuel. But if you’re continually eating more calories than your body needs, then – it goes without saying – that your body won’t be tapping into its fat stores for fuel.
- All the extra weight you lose quickly within the first few weeks on the diet is just water weight – not body fat.
- When total calories and protein intake are equated, keto diets don’t show faster weight loss in comparison to other diets.
- Ultimately, fat loss is all about calorie balance.
Why the keto diet will probably backfire on you
For anyone looking to cut carbs out of their lives, there are also other health considerations to keep in mind. The diet does create an unnecessary aversion to nutritious, yet high-carb foods like fruit, sweet potatoes, beans, lentils, and whole grains, after all.
Keto diet side effects explained: keto flu symptoms
For many people who attempt the ketogenic diet, they experience ‘keto flu symptoms’ when their bodies are still adapting to the diet (i.e. first few weeks).
So, what is ‘keto flu?’ Well, just to be clear, it doesn’t have anything to do with the common flu at all.
Instead, the ‘keto flu’ refers to the following slew of side effects that you could experience when going keto.
In comparison to high-carb diets, the keto diet seems to increase your risk of persistent hair loss (28, 29, 30). That said, studies indicate that the primary reason behind the hair loss is that of nutritional deficiency (31, 32, 33, 34, 35). So, if you’re on the keto diet but eating a nutritionally-varied diet, you’re likely to keep your hair.
Both long- and short-term studies (spanning 13 to 24 weeks) find more headaches among keto diet subjects (36, 37, 38). To be exact, 22–80% of keto subjects report a headache at some point. And frankly speaking, that’s a lot. For reference, only 13 – 46% of low-fat dieters report headaches in the same period.
The keto diet seems to increase the chances of you having difficulties when you’re doing, um, number two in the toilet (39, 40, 41, 42, 43). Studies indicate that roughly 10 to 63% of people get constipated when they go keto. Why? Well, because carb-filled foods contain the highest amount of dietary fiber and water – both crucial factors for a smooth bowel movement (44).
While admittedly not as common a side effect, diarrhea can also occur as there may be a delay in enzymes that digest fat to respond to the increasing amount of fat in your diet (45, 46, 47). The fat that doesn’t get broken down in your small intestine (the way it’s supposed to) travels into your colon and activates bacteria that can lead to gas, bloating, and fat in the stool – thereby causing loose stool.
Just a fair warning: according to some keto adherents, bad breath (also known as the ‘keto breath’) is also a part of the ‘keto flu.’ And this atrocious breath might be caused by the presence of acetone – a ketone and byproduct of fat metabolism – in exhaled breath (48, 49, 50, 51, 52).
But of course, these side effects will vary from person to person: you may get all the side effects, only experience a few, or be one of the fortunate ones and feel great on the keto diet.
Nonetheless, you may have noticed that while concerning, none of the mentioned side effects pose serious health risks. So – does that mean that the keto diet is safe? Or better yet, is it healthy in the long-run?
- You may experience ‘keto flu’ symptoms such as hair loss, headaches, constipation, diarrhea, and bad breath when you’re on the keto diet.
- These keto diet side effects vary between individuals.
Is keto diet safe?
It’s crucial to note that for most people, the keto diet seems pretty safe (53). But when it comes to specific health-related questions, there seem to be several unanswered questions.
For example, on the bright side, we have substantial evidence showing that a keto diet reduces seizures in children (sometimes as effectively as medication) and improves blood sugar control for type 2 diabetes in the short-term (54, 55, 56).
Yet, on the other hand, we see controversy when it comes to the diet’s effect on cholesterol levels, liver health, and dyslipidemia (a medical condition where there’s an abnormal level of fat in the blood) (57, 58, 59).
Also, the ketogenic diet can be rather heavy on red meat and fatty, processed, and salty foods – think hot dogs, bacon, and lamb shank.
Research has consistently indicated that the over-consumption of these notoriously ‘unhealthy’ foods and under-consumption of ‘healthier’ foods (like nuts, seeds, vegetables, fruits, and whole grains) are linked with death from heart disease, stroke, and type 2 diabetes (60).
So, even if we don’t necessarily have a causal link or recommended limit, this is still a crucial point to note.
Ultimately, since we don’t have any research that’s followed participants for more than a year, it’s hard to confirm long-term safety with certainty.
But for reference’s sake, complications seen with children maintaining a keto diet for epilepsy, for example, included kidney stones, constipation, gastrointestinal issues, pancreatitis, and vitamin D and calcium deficiencies (61, 62).
- The keto diet can reduce seizures in children and improve blood sugar control for type 2 diabetes.
- But adhering to the keto diet without moderating intake of certain fatty and processed foods could lead to chronic health issues.
- Ultimately, even though the keto diet seems pretty safe for most people, we don’t have any research that has looked at the long-term health effects of the diet.
Is the keto diet useless?
Well, the keto diet isn’t useless; it can genuinely help with weight-loss. And isn’t that – honestly – the whole point of going on a diet?
Keto diet can be helpful
See, the ketogenic diet has appetite-blunting effects – meaning that the diet could help you eat fewer calories each day.
Hang on. Didn’t we just say that the keto diet is no better than other diets (63, 64, 65, 66, 67)? Well, yes – only if we keep the number of calories the same between them.
In the real world, the ketogenic diet can kill your drive to eat, thus helping you consume fewer calories. And if you’ve been paying attention, you’d know that calorie balance (i.e. whether you’re in a deficit or surplus) is the most important thing for fat loss (68).
So – why does the keto diet blunt your appetite? Well, that’s really because of two things:
- Ketone bodies (byproducts of fat breakdown) seem to curb appetite (69, 70, 71, 72, 73).
- Increased protein intake is often a result of following the ketogenic diet (74, 75, 76). And research indicates that eating more protein alone can curb your drive to eat (77, 78, 79).
But only if you adhere to it long-term
As you can see, the keto diet can indeed be a useful strategy for weight loss. If you can stick to it, that is. The fact is that there’s not much research on the overall sustainability of ketogenic diets.
Unfortunately, people often find it challenging to maintain a low-carb diet long term. Even if you have figured out how to meal prep effectively, life has a way of screwing it up. Vacations, work functions, social occasions – there’s bound to be at least one scenario in which you‘ll find yourself eating higher-carb foods.
And the same reasons why you see immediate weight loss on carb-restricted diets is the same reason why you see immediate weight gain after adding a seemingly harmless sandwich back onto the plate. The water-weight piles back on instantly with glycogen storage (80, 81, 82).
Think about it: any diet that’s as extreme as keto (no bread, no pizza, no alcohol!) won’t translate well into regular, everyday life. For most people, it potentially eliminates all joy associated with eating ‘real’ food and living life.
- The keto diet can blunt your appetite, causing you to eat fewer calories than you would have on other diets – thereby causing weight loss.
- But the keto diet is extremely restrictive and unsustainable over the long-run.
Find what’s sustainable for you
Ultimately, evidence suggests that the keto diet can be useful for short-term weight loss. But little is known about its long-term safety and efficacy.
At the end of the day, enjoyment and adherence are the two-key lifestyle change techniques that will produce the best outcomes for any eating plan (83). It’s always important to establish a healthy relationship with food right from the start.
Find an approach that’s enjoyable, healthy, and maintainable – for you. Figured out a way to go keto without feeling miserable or cutting out too many necessary nutrients? Bravo.