I don’t know about any of the people reading my blog, but being quite heavily into the weight loss community I notice one diet is doing the rounds at the moment, everywhere I look someone is mentioning keto. Keto is often combined with Intermittent Fasting, so that is probably doubling my exposure to it, but honestly I can’t get away from it.
Always curious to investigate other ways of weight loss, I have looked into it to try to get an understanding as to what it is, how it works, why people are so crazy about it and what the impacts of it are.
What is the Keto diet? To understand that it’s best to take a few steps back to describe how the body works. Generally, on a standard diet, the body burns sugar for energy. This sugar is ingested in the forms of carbohydrates (and some protein but mainly carbs). Our body converts this to glucose and and uses this as it’s main energy source. Excess carbohydrates are stored as glycogen in the liver and muscles. When you exercise, and on a normal day to day basis when your body needs energy it gets it from these sources as they are readily available.
Eventually though your glucose and glycogen stores run out, at which point your body moves to it’s backup energy source, your fat stores, stored as adipose tissue on your body. Energy is taken from your fat cells, it is lost via bodily fluids (sweat/breath/urine). When it comes to weight loss, you want to take in less calories than you burn, therefore you use up your glucose and glycogen, then you use the fat, and over time you will get lighter. If you exercise more you will also burn more, but it mostly comes down to how much you eat. This is why people can lose weight while eating McDonalds (supersize me anyone?).
So, back to keto. The aim of Keto is to get your body into “Fat burning” mode. Instead of burning glucose and glycogen as your primary fuel source, you force your body to burn fat (broken down fat known as ketones) directlly, this is done by eating a large amount of fat (60 – 75%), protein (15-30%) and a very low amount of carbs (5-10%). As you are taking in so little carbs, you really shorten the glucose and glycogen phase of burning. It takes adjustment and has side effects, but once in this mode people report feeling great, full of energy, and many find it a successful way to lose weight.
There are a few ways of reaching the fat burning stage, as mentioned previously exercising while eating at a calorie deficit will burn fat, but also intermittent fasting is another choice. When you don’t eat for extended periods of time eventually you run out of glucose and glycogen and your body has to burn fat for energy. Then, when you eat carbs you replenish the glucose and glycogen until towards the end of the next fast.
The Keto diet and Intermittent Fasting combined keto foods aim to keep you in the fat burning stage at all times, keeping carbohydrate low so to keep fat being burned. It all sounds great so far, fat burning, increased energy, weight loss..that’s what you want isn’t it? Well, yes… but there are downsides to the keto diet that hardcore keto proponents try to ignore or disregard.
A diet high in fat and protein is not good for longevity. Although there does appear to be some who argue this, the vast majority of doctors agree, high cholesterol (much of which is eaten via saturated fat) is one of the leading causes of heart disease. (Here, here and here, and about a million other places, and here is a NHS page speaking out against a study which says cholesterol does not cause heart diesease). I am not claiming that all cases of high blood cholesterol is caused by eating saturated fat, there are certainly people who can have high cholesterol naturally, just that actually eating saturated fat does correlate with an increase in cholesterol.
Most ingested saturated fat is eaten via animal products, although some plant oils (coconut oil for example) also contribute to this. So what does eating a diet at 60-75% fat (mostly saturated) do for people in the long term? Unfortunately there aren’t many long term studies on this, however the Inuits (often held up as an example as people who ate almost all fat and remained healthy) did in fact suffer from heart disease and strokes, and their life expectancy was around a “decade shorter among native populations”.
One thing that is known from scientific studies is that groups who follow a plant based diet generally have a longer life expentency than those who don’t, and that those to raise their intake of animal protein raise their risk of all cause mortaility overall. Of course, you can make the argument that we will all die eventually, but I would guess for most people (certainly for myself and my desires for my children), a long, healthy life is the goal.
Even taking away the longevity argument, a keto diet is difficult to follow, anecdotally people struggle in the medium – long term with almost completely avoiding carbs, and report side effects such as hair loss, bad breath an leg cramps. The lack of fibre in the diet can also be a cause for concern when it comes to digestion. Additionally, if you are following a keto diet as a non-vegan ,in an attempt to fit in all the animal products and fat you are responsible for the deaths of animals and unecessary destruction of the planet on a larger scale that even a standard diet.
You can follow a ketogenic diet as a vegan although it is more of a challenge if you are not eating fatty animal products. Although, with the known down-sides of eating so much fat, I struggle to understand why anyone would want to, apart from the reason of enjoying fatty foods (thanks evolution!), and wanting to hear good news about your bad habits.
The main reason I follow Intermittent Fasting though isn’t for ketosis. I’m not sure whether I fast for long enough to reach ketosis, but fundamentally, I can’t find any research saying ketosis (being a fat burner) itself is actually bad for you. It is the dietary route of doing it that hurts your body in the long term. I like to think that with intermittent fasting I get the benefits (weight loss, increased energy etc) without the downsides (heart disease and stroke increased risk, arterial clogging).
I get the freedom of not thinking about food all day and the ability to eat a large evening meal. I have always enjoyed this, but that large meal with two other meals during the day inevitably leads to too many calories and weight gain, whereas that large meal with minimal other food can still equate to weight loss.
My disclaimer to this post is that I am not a nutritionist, nor a scientist. Just an interested person who has read and listened to many podcasts about the subject. I would suggest anyone following a keto diet to not automatically take everything at face value, in fact, that goes for anyone following any diet. Read, understand the science to the best of your capability.