Are carbs really making us fat and sick? Is it possible a high-protein, high-fat diet is the holy grail of a healthy body? It’s time to separate the fact from the fiction.
Chances are you’ve heard about the ‘Ketogenic Diet’ or keto diet, which is a reincarnation of super low carbohydrate diets such as the Atkin’s Diet or the South Beach Diet. And, credit where credit is due here – the advocates of this dietary framework have been extremely clever with their marketing, resulting in wide circulation of their key claims. Given these claims centre on promises for a body primed for burning fat and better blood glucose control, it’s easy to see why many people who want to lose weight or manage diabetes find this diet attractive. But are these claims supported by science? I think it’s time we separate fact from fiction when it comes to the keto diet.
Before we jump into the science, it’s important to understand the basic premise of this dietary framework. A ketogenic diet consists of a very low amount of carbohydrates (20–50g per day), moderate amounts of protein, and a very high amount of fat (70% or more of total calories). Because the body is deprived of its primary fuel source, glucose, it transitions to a state of ketosis, whereby it begins to produce compounds called ketones that are used for energy. Essentially, this is a survival mechanism that enables the body to keep creating energy from a secondary source – fat – until the person finds carbohydrates again. As you can imagine, this would have been very beneficial for our ancestors when food supply was not guaranteed. But how healthy is it as a strategy for weight loss or managing lifestyle disease?
Fat burning versus fat loss
In theory, the Ketogenic Diet claims to switch your body from one that produces energy from glucose (carbohydrates) to a body that ‘burns fat’ as its energy source. So, that would mean greater fat loss, wouldn’t it? Happy days! But unfortunately, that’s not how it works. Unless you are in a calorie deficit (eating less calories than you use), a state of ketosis simply uses energy from dietary fat, not stored fat. And fat burning is very different to fat loss. This is a point that many keto advocates gloss over. To tap into your body’s fat stores, you need to burn more calories than you consume. In fact, a metabolic ward study that compared a ketogenic diet with a high carbohydrate diet of the same total calories found zero difference in body fat loss. The people in this study, just like anyone in ketosis, used fat as their primary source of energy. But regardless of diet, unless they were in calorie deficit they did not burn stored body fat. So unless you are in calorie deficit on the keto diet, you’re simply using the fats in the avocado or coconut oil you just ate (or bacon and butter for non vegans).
However, people do seem to anecdotally lose weight when they switch to a ketogenic diet. Why? There’s two major reasons. The first one is obvious – glycogen. The average person stores about 500 grams of glucose in their muscles as glycogen. Each gram of glycogen attracts three grams of water. Therefore, when you switch to a ketogenic diet your body uses all of its glucose stores before going into a state of ketosis. This process alone results in a drop of about two kilograms. But this is purely scale weight and is not a reflection of fat loss. I can understand how this very sudden drop in scale weight acts as an initial motivator and hooks people in. Unfortunately though, it’s nothing more than a facade, and many studies show that maintaining glycogen stores is crucial for optimal recovery, performance and overall exercise capacity.
The second reason the keto diet helps people lose weight is actually a good one. Because it encourages only consuming a miniscule amount of carbohydrates per day, by default this means people cannot eat their favourite refined junk foods. So, all of a sudden chocolate bars, doughnuts and fried potato chips are off the menu. This sees many people fall into a calorie deficit. But let’s remember – this isn’t some magic weight loss process. You can in fact remove refined junk foods while still eating healthy carbohydrate-rich foods and achieve a similar result.
Can a keto diet reverse insulin resistance?
Perhaps the most concerning of the claims made by keto advocates is the idea that the diet can reverse insulin resistance and Type 2 Diabetes. Properly addressing the science surrounding this is outside of the scope of this story, however, to reverse insulin resistance or Type 2 Diabetes you need to improve your body’s ability to tolerate carbohydrates. This can be achieved by changing the types of food you eat with or without the presence of weight loss. While a ketogenic diet may help control blood glucose, without weight loss, it does not improve insulin sensitivity. So why is this a problem? It means you need to continue to eat a low carbohydrate diet for the rest of your life because you have not addressed the underlying cause of the disease. In fact, this is likely to have been made worse by higher amounts of ectopic fat stores in muscle and liver cells.
On the other hand, unlike the ketogenic diet, a whole food plant-based diet that is low in fat has been shown to improve insulin sensitivity without requiring weight loss. Remember, to treat the cause of insulin resistance or Type 2 Diabetes, you need to improve tolerance to carbohydrates – not simply remove them. Changing the food a person eats can achieve almost instant changes in insulin sensitivity. Several trials have been published whereby Type 2 Diabetics who adopt a whole food plant- based diet that is low in fat have been able to completely come off their medications. The other thing to keep in mind is that the number one cause of death for diabetics is cardiovascular disease. The lowest levels of cardiovascular disease are consistently found among populations that get the majority of their calories from whole food plant sources of carbohydrates. So that then begs the question: What is the cost associated with leaving healthy carbohydrate-rich whole foods off the menu like whole grains, fruits and legumes for the rest of your life if you are following a keto diet to manage insulin resistance?
How does a keto diet affect risk of chronic disease?
Let’s jump straight to the punchline here. A ketogenic diet will increase your risk of chronic disease. There are no populations who consume a low-carbohydrate diet that show longevity. Research instead suggests people adopting such diets long term have a higher risk of premature death. Low-carb advocates will talk about the Inuit Eskimos, a population who traditionally consumed a very high fat diet made up of almost exclusively animal products to disprove this. However, it’s been well documented that claims this population experienced a low incidence of cardiovascular disease were based on anecdotal rather than empirical scientific evidence. In fact, compared to non-Inuits from nearby populations, the Inuit population actually have the same risk of heart disease, twice the risk of stroke, and a shorter life expectancy of approximately 10 years. Studies have even reported the presence of heart disease in frozen Eskimo mummies dating back to over 1,000 years ago.
Basing recommendations for a low carbohydrate diet on anecdotal evidence from the Inuits ignores what we know about high fat diets and cholesterol as well as a plethora of evidence that we have on how the longest living populations in the world eat. The typical ketogenic diet contains foods associated with increased LDL cholesterol and increased risk of cardiovascular disease, and that’s exactly what the science shows. A recent study compared a ketogenic-style diet (less than 20g of carbohydrates per day) to a control diet and found the low-carbohydrate diet subjects experienced a 44 per cent increase in LDL cholesterol in just three weeks.
We also know that people who consume higher amounts of dietary fibre (found in carbohydrate-rich plant foods) and lower amounts of total dietary fat (particularly saturated fat) experience significantly less risk of developing major chronic diseases. Adopting a ketogenic diet, and therefore restricting your dietary fibre intake, is certainly risky business when it comes to overall health.
What about the sustainability of keto diets?
One of the biggest problems with low- carbohydrate diets is that they are not sustainable and almost always lead to long term weight gain. We know from several studies, randomised trials, and population studies, that adopting a whole food plant-based (or even plant-focused) diet helps people maintain a healthy body weight without having to calorie count. And, when talking about sustainability, we also need to touch on the health of our planet. Typically, a ketogenic diet includes large amounts of animal products (such as fatty cuts of meat, full-fat dairy products, and eggs), which we know require greater water inputs and produce more greenhouse gas emissions than plant-based foods. For example, for an equal amount of protein, the production of cheese produces approximately fourteen times more greenhouse gas emissions than that of legumes. In its typical form, a keto diet places a greater strain on our environment. And while a vegan keto diet at a high level appears to be better for environmental health and animal welfare than a typical keto diet, there is still a lot more science needed to before we can confidently recommend it as a safe and healthy dietary framework to follow long term.
In summary, there is no evidence to suggest that a typical ketogenic diet is better than any other diet for weight loss when calories are matched. And there is zero data to suggest this is a healthy way to eat long term. A carbohydrate-rich whole food plant-based diet, on the other hand, is sustainable for both you and the planet, and comes with a host of health benefits. My recommendation is to look past the sexy marketing messages of the ketogenic diet and veto the keto.