Chances are in the past few years you have come across the Ketogenic
or ‘Keto’ Diet – which is nothing but a reincarnation of the super low
carbohydrate diets such as the Atkins & South Beach diets. Credit
where credit’s due – the proponents of this dietary framework have been
extremely clever with their marketing strategy which has resulted in a
wide circulation of their message. Keto proponents claim that this diet
can effectively turn a body into an efficient ‘fat-burning’ machine that
is also better at regulating blood glucose. These are certainly
attractive claims for anyone wanting to stay thin (which, let’s be
honest, includes most of us) and particularly anyone who suffers from
any type of Diabetes, so I completely understand why many of us are
turning to this diet as some form of panacea. After all, as a society,
we have never been more overweight, and rates of Type 2 Diabetes – which
is a lifestyle disease
– are soaring across the world. But being the science nerd that I am – I
really wanted to separate fact from fiction and understand where the
science lies. Are these claims supported by the literature? Beyond
marketing and agenda-setting, what is the truth about the Keto Diet? To
do this, I set out to answer 4 questions:
- Is the Ketogenic Diet better for weight loss than other diets?
- Is the Ketogenic Diet better at reversing insulin resistance than other diets?
- Does the Ketogenic diet reduce one’s risk for chronic disease?
- Is the Ketogenic Diet sustainable?
Fundamentals of the Ketogenic Diet
Before we jump into the science, it’s important to understand the specifics behind this dietary framework. Followed properly, a ketogenic diet consists of a very low amount of carbohydrates (20-50g/day), a moderate amount of protein, and a very high amount of fat (70% or more of total calories). By depriving the body of glucose, the body’s primary fuel source which is provided by carbohydrates, the body 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 whereby the body is able to keep creating energy using a secondary source, derived from fat, until the person can consume carbohydrates again. As you can imagine, this process would have been extremely useful for our ancestors when food supply was scarce and their next meal was rarely guaranteed. Today, however, with the abundance of food we are spoiled with in the western world, this survival mechanism is simply made redundant.
1 – Is the Ketogenic Diet better for weight loss than other diets?
In theory, the thinking goes, if a Keto Diet can make a body switch
from producing energy from glucose to a body that “burns fat”, this
would mean greater fat loss and thus a leaner body mass. Less fat around
the thighs, bum and/or waist – happy days! An attractive theory no
doubt – but unfortunately, that’s not really how it works. Unless you
are in a calorie deficit, when in ketosis you are simply using the
energy from dietary fat, not stored fat. This is a distinct point that many keto proponents often fail to mention. Fat burning is very different from fat loss. In
fact, to actually tap into your body’s fat stores and shed some weight,
you need to be burning more calories than you consume (a calorie
deficit). This is why a study that compared a ketogenic diet to a high
carbohydrate diet with equal calorie intake found zero differences in
body fat loss . So
yes, people following a strict Keto diet will be in ketosis and thus
utilise fat as their primary source of energy, but, just like any other
diet, unless they fall into a calorie deficit, they are not burning stored body fat – just the fat they are eating.
So why then do people seem to anecdotally lose weight when they switch to a ketogenic diet? There are two major reasons that explain this phenomenon. The first and super obvious one is glycogen.
The average person stores about 500g of glucose in their muscles as
glycogen. Each gram of glycogen attracts 3g of water. Thus, when you
switch to a ketogenic diet, the body utilises all of its glucose stores
before falling into a state of ketosis – this process alone results in a
drop of about 2Kg. But friends, it’s important to note this is purely scale weight and is again not a reflection of actual fat loss.
I can see how this very sudden drop in scale weight acts as an initial
motivator and is what hooks people to the Keto Diet. However, far from
being a miracle diet, it is nothing but a misleading occurrence, and a
somewhat dangerous one: many studies have shown that maintaining
glycogen stores is absolutely crucial for optimal recovery, performance
and overall exercise capacity .
The other reason that the Ketogenic Diet helps people lose weight,
which I actually think is a positive aspect, is that by encouraging the
consumption of an extremely limited amount of carbohydrates per day, it
means that by default people cannot eat their favourite refined junk
foods. All of a sudden, chocolate bars, doughnuts, pastries and fried
potato chips are categorically off the menu. This is likely going to
result in a significant calorie deficit for a lot of people. But it’s
important to appreciate that this isn’t some magic weight loss process
and you can in fact remove heavily refined junk foods (e.g jelly beans),
whilst still keeping healthful carbohydrate-rich foods in the game (e.g
black beans), and also lose weight.
2 – Is the Ketogenic Diet better at reversing insulin resistance than other diets?
Perhaps the most concerning of the claims made by keto proponents is
the idea of “reversing insulin resistance and Type 2 diabetes.”
Addressing the totality of the science surrounding Type 2 Diabetes is
beyond of the scope of this article (this topic was addressed in an article I wrote with Dr Michelle McMacken) however, in short, to reverse insulin resistance or Type 2 Diabetes it is necessary to improve one’s someone’s ability to tolerate carbohydrates.
Two of the major ways we can achieve this is by changing the types of
food someone eats with or without the presence of weight loss. A
ketogenic diet may help control blood glucose, however, without weight
loss, it will not improve insulin sensitivity. What’s the problem with
this? It means one would need to continue to eat a low-carbohydrate
diet for the rest of their life as the underlying cause of their disease
has not been addressed, and in fact, is likely to have been made worse
by higher amounts of ectopic fat stores in muscle and liver cells.
On the other hand, unlike a ketogenic diet, a low-fat wholefood
plant-based diet has been shown to improve insulin sensitivity even without
weight loss. By merely changing the food one eats it is possible to
achieve an almost instant change in insulin sensitivity. In fact,
several trials have been published where Type 2 Diabetics who adopt a
low-fat plant-based diet have been able to completely come off their
It’s also important to keep in mind that the #1 cause of death for
diabetics is cardiovascular disease and that the lowest levels of
cardiovascular disease are consistently found among populations that get
the majority of their calories from wholefood plant sources of
carbohydrates such as the Indigenous Tsimané people in Bolivia and
plant-based Seventh Day Adventist’s in California & Canada [7,8].
3 – Does the Ketogenic diet reduce one’s risk for chronic disease?
The evidence is clear: across the world, no population consuming a
low carbohydrate diet fares well in terms of longevity, and in fact,
research suggests that in the long-term, people who adopt such diets
have a higher risk of premature death .
Low carb proponents often point to the ‘Inuit Eskimos’, a population
who consume a very high-fat diet made up of almost exclusively animal
products, to defend their position. However, it’s been well-documented
that the original claims of this population experiencing a low incidence
of cardiovascular disease were based on anecdotal rather than empirical
scientific evidence .
In fact, compared to non-Eskimos 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 around 10 years . Studies going back over 1,000 years have also reported the presence of heart disease in frozen Eskimo mummies .
This is likely because a high-fat diet made up of almost exclusively
animal products contains foods associated with increased LDL cholesterol
and cardiovascular disease risk and that’s exactly what we see in the
A recent study compared a ketogenic style diet (less than 20g of
carbohydrates per day) to a control diet and in just 3 weeks found that
the subjects on the low-carbohydrate diet experienced a 44% increase in
LDL cholesterol .
Overall, 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. We know that people
who consume higher amounts of dietary fibre, a nutrient found in
carbohydrate-rich plant foods, and lower amounts of total dietary fat,
particularly saturated fat, experience a significantly reduced risk of
developing major chronic diseases . Adopting a ketogenic diet, and therefore restricting your dietary fibre intake, is risky business.
4 – Is the Ketogenic Diet sustainable?
One of the biggest problems with low carbohydrate diets is that they
are not sustainable and that in the long run, they almost always lead to
weight gain. On the other hand, we know from several studies,
randomised trials and population studies that adopting a wholefood
plant-focused or exclusive diet helps people maintain a healthy body
weight without having to count and track calories [2,17].
Finally, when talking about sustainability we need to touch on the
health of our planet. Typically, a ketogenic diet is made up of a large
number of animal products (fatty cuts of meat, full-fat dairy and eggs)
which we know require far greater water inputs and produce significantly
more greenhouse gas emissions than plant-based foods .
For example, for an equal amount of protein, the production of cheese
produces approximately 14 x more greenhouse gas emissions than that of
In summary, there is no evidence to suggest that when calories are
matched a typical ketogenic diet is better than any other diet in terms
of weight loss, we have no data to suggest its a healthful way to eat in
the long term, and in its typical form it’s a diet that places great
strain on our already severely damaged environment. What about a vegan
keto diet? While at a high level it appears to be better for human
health, planetary health and animal welfare, there is still a lot more
science needed to before one can confidently recommend it as a safe and
healthy dietary framework to follow long term.
My recommendation is to look past the sexy headlines and adopt a carbohydrate-rich wholefood plant-focused or exclusive diet that is sustainable for both you and the planet and at the same time will help you achieve the health & performance goals you desire. To help identify what this might look like, I have developed a science-based Healthy Plant-Based Food Pyramid so you can easily construct countless delicious meals while making sure you are fueling your body the right way.
 Hall KD, Chen KY, Guo J, Lam YY, Leibel RL, Mayer LES, et al. Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. Am J Clin Nutr 2016;104:324.
 Barnard ND, Cohen J, Jenkins DJA, Turner-McGrievy G, Gloede L, Green A, et al. A low-fat vegan diet and a conventional diabetes diet in the treatment of type 2 diabetes: a randomized, controlled, 74-wk clinical trial. Am J Clin Nutr 2009;89:1588S.
 Kaplan H, Thompson RC, Trumble BC, Samuel Wann L, Allam AH, Beheim B, et al. Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study. The Lancet 2017;389:1730–9. doi:10.1016/s0140-6736(17)30752-3.
 Wright N, Wilson L, Smith M, Duncan B, McHugh P. The BROAD study: A randomised controlled trial using a whole food plant-based diet in the community for obesity, ischaemic heart disease or diabetes. Nutr Diabetes 2017;7:e256.