I’ve had tons of people - including my own doctor - ask me about the Keto diet recently. It’s the newest highly restrictive diet! A fad? In terms of weight loss, probably.
My first impression was – this is silly. Restrictive, unsustainable, malnourishing. But I did my job and researched the hell out of it. So here are the straight up facts before I give my informed opinion.
HOW IT WORKS
Your body’s preference for fuel is carbs, then fat, then protein as a last resort. Carbs are used for short term energy because they are easiest for your body to break down. Fat is your reserve for when that runs out.
Following a Keto diet switches your body’s main fuel source from carbs to fat. By removing most carbs from your diet, you can quickly deplete the glycogen (carb) stores in your liver and muscles. Your body will then start using fat from your diet and tissues for fuel, a state called ketosis.
In other words, you starve your body of carbs without actually starving, and your body switches from sugar burning mode to fat burning mode.
Ketosis = fat-burning mode
You may have heard that your brain can only run on glucose, and this is partially true. Some parts of your brain do require glucose, and others can use ketones (a byproduct of ketosis). Luckily your body can use protein to make its own glucose, because it's a miraculous machine. So technically you can live with very little carbs, not that you necessarily should.
So how do you actually lose weight? Hormonal changes and the satiating effect of fats should reduce your appetite, decreasing your caloric intake. For example, it reduces your production of ghrelin, the hormone that makes you feel hungry.
WHAT ARE YOU ALLOWED TO EAT?
The Keto diet is an extremely low carb, high fat diet (also called LCHF). Think Atkins on steroids, with a focus on fat instead of protein.
CARBS: You need to stay under 20g of carbs per day – the amount found in one banana. At first it will involve tracking your carbs meticulously with something like MyFitnessPal. Even vegetables have a tiny amount of carbs in them, so by the end of the day you can't actually afford to have the banana.
FAT: Have as much fat as you want (saturated, unsaturated, medium-chain triglyceride oil). Many people incorporate MCT Oil into their diet because it increases ketone production and fat loss. There are tons of recipes online for ‘fat bombs’, aka high fat snacks. Think butter in your coffee.
PROTEIN: Eating too much protein will hinder ketosis, so you still need to keep an eye on this. It can be challenging to meet your fat target without overdoing protein.
This diet can provide all the essential nutrients if planned correctly. You need to make an effort to get enough fiber, electrolytes (Magnesium, Chloride, Sodium, Potassium), Vitamin D, Calcium, Selenium, and Zinc. Proponents of the diet recommend LOTS of water, added salt, a multivitamin, and other vitamin or mineral supplements if you aren’t getting them all through food. Cutting out all grains, milk and fruit makes it extremely tricky.
There are also targeted and cyclical versions for cardio and strength training. Some vegetarians also follow the diet. Others follow a 'moderate Keto diet' with 30-50g of carb, making room for more starchy veg and fruit.
The Keto diet was first used to treat children with epilepsy, and it worked like a charm. New research has shown promise in treating other neuro diseases like Alzheimer's. It's also been studied as a treatment for certain cancers, but research is in its infancy (read the health risks below for less promising news on the cancer front). So what about benefits for otherwise healthy people?
Initial weight loss is rapid. As you deplete your body’s glycogen (carb) stores you lose water with it. This diet is diuretic so it makes you pee like a racehorse. Next you’ll start burning into your fat stores and loss slows down to 1-2lbs a week. In 6 month trials subjects do lose more weight over 6 months than those on a low fat diet, even if they eat the same amount of calories. However...
After 1 year, Keto subjects only lost 1-2 lbs more than those on a low fat diet.
Fat is satiating because it contains 9 calories per gram vs only 4 in carbs and protein. Many Keto dieters find they only need to eat 1-2 times a day to feel satisfied. Those hormone changes I mentioned also keep appetite low.
Blood Sugar Regulation
The Keto diet has been shown effective in preventing diabetes for those who are at high risk of developing it. But then again, so is any combination of diet and exercise that results in weight loss. Using Keto to treat diabetes has potential, but that's a whole other story. Note: if you're on diabetic medications or insulin do NOT start a keto diet without medical supervision.
Your body becomes equipped for easier access to your fat stores for fuel. This allows for a more steady stream of energy during the day, even if you go for long periods without eating.
Some people start a Keto diet solely for this benefit. There are multiple ways ketosis can help brain function. Without getting into the specific neurobiology, ketones help balance neurotransmitter production for optimum focus. They also help your brain cells produce energy more efficiently than glucose.
Thanks to Keto staples like fish, avocado, and coconut oil, the diet provides a healthier balance of omega fats than the average Western diet. The proper ratio of omega-3:omega-6 fats help achieve optimal brain function.
Increase in Good Cholesterol
Good cholesterol (HDL) cleans the 'gunk' out of your arteries. HDL increases when you eat healthy fats included in the keto diet, from foods like nuts and fatty fish.
Reduced Blood Pressure
Blood pressure is reduced with weight loss. Keto and low-fat dieters see equal improvements in blood pressure.
Clears Up Acne
Via hormonal changes.
SHORT TERM SIDE EFFECTS
There are lots of harmless, but seriously unpleasant symptoms when transitioning to ketosis. During the first 4-5 days of strictly following the Keto diet, people often experience fatigue, headaches, nausea, constipation, brain fog, moodiness, reduced athletic performance, cramps and heart palpitations.
You may notice some side effects are the exact problem dieters are trying to solve in the first place. Luckily they are all short term or can be managed with lifestyle changes. The reasons for this plethora of side effects are:
1) It takes time for your body to adjust to your new fuel source. It will deplete all your glycogen (carb) stores quickly, then have a hard time digesting all the fat you’re ingesting. After 4-5 days your body will adjust by producing enough digestive enzymes to break down fat for energy.
2) The keto diet is diuretic. Your fluid/electrolyte balance will be thrown off kilter at first. That’s why you’ll see beginner guides recommending Gatorade and lots of added salt during the transition phase. You may need to supplement specific electrolytes like potassium to manage cramps and heart palpitations. Oh and drink tons of water (and maybe Metamucil) to keep things moving.
P.S. another side effect is ‘Keto breath’. Ketones are excreted via urine and exhalation, so your breath will smell and you'll have a metallic taste in your mouth. This too is supposed to disappear over time.
Less common risks include breastfeeding issues, gallstones, kidney stones, hair loss, and rashes. This diet is not safe for women who are pregnant or breastfeeding.
LONG TERM SIDE EFFECTS
Dysbiosis (Damaged Microbiome)
Think of the gut as a world with 10 trillion inhabitants, and they’re living in a little dystopian world of a tummy. Your gut is happy when you reduce your intake of refined carbohydrates, but cutting out all carbs can be damaging. Healthy gut bacteria feed off of fiber, which can be in short supply when you cut out major sources like fruit, legumes and grains. Diets high in meat can also damage gut flora.
As mentioned many studies do show improvements in cholesterol and blood pressure. But it can also raise your bad cholesterol. This may be from high saturated fat intake. There’s no consistent evidence here, but I’d steer clear of this diet if you have a family history of heart disease. If you aren't getting enough fiber you may also be at higher risk of heart disease.
Risk of Digestive Cancers
Keto doesn't HAVE to be high in red meat, but it often is. If you have been diagnosed with colon cancer, eating large amounts of meat can be very harmful. Especially processed red meats like bacon, which increase your risk of developing it in the first place. If you have had gallbladder cancer or had your gallbladder removed, high fat intake may create more problems.
Remember how I said parts of the brain require glucose to function? Well the part responsible for thyroid hormone production is one of them. Cutting out ALL carbs can cause the thyroid to struggle, leaving you tired and with a slower metabolism. It also needs zinc, magnesium and selenium, nutrients I mentioned can be lacking in a Keto diet. There is a lack or research in the area, but it remains worth noting.
Reduced Bone Mineral Density
This diet can be lacking in calcium and magnesium which are essential for bone health. This is a risk that can be negated by careful diet planning and supplements. Research linking Keto to osteoporosis is inconsistent.
The research is not extensive but studies have not been shown any special benefit for athletes. We know for sure that those following Keto vs control groups lose more lean body mass. However lean body mass is comprised of muscle, glycogen and water. So we aren't sure if muscle itself is being lost. The consensus is that you can certainly build strength while on Keto, but it may hinder your efforts to reach peak performance.
A DIETITIAN'S OPINION
The physiology makes sense. If you follow this diet you can definitely lose weight, along with some added benefits. But just because it works ‘in theory’ doesn’t mean it works in everyday life, or that it's healthy in the long run.
Using this diet for weight loss purposes has only recently become popular so the research hasn’t caught up yet. While some side effects can be avoided with careful planning, there are still concerns in the long run.
Even if there was no question this diet was safe, it is SO STRICT that it's unsustainable for the vast majority of people. The point of a lifestyle change is that it's for a lifetime, or you'll regain all the weight you lost as soon as you quit. There's a risk of developing or worsening disordered eating patterns as well. There are ways to experience all the touted benefits without restricting carbs so drastically.
Keto can work for the right person, so I'm not ruling out its benefits completely. I just believe the ideal candidates for this diet are few and far between. With the explosive popularity of this diet, I'm wary that it will be another hit and miss for most.
It is not ethical to recommend a strict, under-researched diet to everyone because SOME people have success stories. Our environment, behaviours and metabolisms are complex things that vary from person to person. No diet is right for everybody, but this one probably isn't right for you.