Last year, Google Trends recorded a rising interest in “keto diet” as a search term, its place in the mainstream cemented by one influencer endorsement after another. First came the media coverage, then came the keto bars in health food shops and keto-friendly ready meals in supermarket aisles. So, how did this once obscure eating style make it to the top of the dietary podium?
The keto diet was first developed as a treatment for epilepsy, with trials recorded as early as the 1920s. These early incarnations were extremely strict, with 90% of total energy coming from fat and only 10% coming from carbohydrate and protein combined. In absolute terms, this translated as a ratio of 4:1 fat to carbs and protein – essentially a very low carb, low protein, high-fat diet. Meeting this ratio was deemed therapeutic for patients with epilepsy, but only feasible for in-patients under strict supervision and with supplementation. Hence, this is not practical or feasible to replicate in an out-patient or real-life context.
Fast-forward a few decades and in the early ’70s, American physician and cardiologist Dr Robert Coleman Atkins began to apply aspects of keto diets for weight loss, leading to the development of "The Atkins Diet", which is characterised by requiring low carbohydrate levels but without limits on protein or fat. This low carb, high protein, high-fat diet became hugely popular as a weight loss diet, as you could still eat as much meat, cheese, butter etc. as you liked. However, where the Atkins diet received so much criticism is that it – for the most part – didn’t limit protein. Who can forget the famous Atkins burger: a beef patty sandwiched between two chicken burgers. It’s quite bizarre in hindsight!
The modern ketogenic diet – outside of a clinical setting – is typically a "Modified Atkins Diet" (MAD), and is again mainly described as a treatment for epilepsy. This MAD diet restricts carbohydrate more prescriptively to 20g per day, with limits to protein, but is made more achievable by recommending a ratio of 1:1 fat to carbohydrate and protein. In essence, it’s a very low carb, moderate protein, high-fat diet.
That is not to say this MAD diet is easy to follow, though, as limiting carbohydrate to 20g per day is a challenge. The evolution from here was the ketogenic diet as we more commonly know it. In this day and age, we typically look at a macronutrient divide of less than 50g of carbohydrate, moderate protein and high fat.
When we think of ketogenic diets not in their clinical sense, but as a way to optimise health and alter body composition, it really all comes down to this ongoing nutritional feud between pro-fat and pro-carb camps. This binary way of thinking is not at all helpful, but it is a key catalyst for increasing promotion of the keto diet.
Traditionally, we have this idea from one side that fat is bad: it’s energy-dense and contributes to heart disease and obesity. The opposite of that is the carbohydrate-insulin model, which posits that these conditions have nothing to do with fat but are caused by the excess action of insulin we get from carbs, which in turn increases fat storage, leading to heart disease and obesity.
Fronted by American physiologist Ancel Keys, the low-fat model has been the public health message since the 1960s. But regardless, there has been little evidence to show for this message in terms of a change in obesity levels. If anything, obesity has increased, and though deaths from cardiovascular disease have dropped, the prevalence has remained high. Naturally, this has led many commentators to criticise this fat-centric approach, with attempts to dispute the underlying evidence (often wrongly I may add, but that is for another time).
A keto diet proposes a polarising view, prioritising fat. Conventional diets tend to look at reducing energy (calorie) intake, and consequently see a reduction in fat, which at 9 calories per gram is the most energy-dense macronutrient (carbs and protein both total 4 calories per gram).
By contrast, the keto diet is – on the surface at least – not necessarily concerned with calories at a top-line level, but with reducing carbohydrate and replacing it with fat as your main fuel. In doing this, you’re sold the notion that your metabolism is forced to reorganise to burn more fat and to supplement where you can via ketones, despite not necessarily eating less.
Want to know more? Dr Adam Collins’ five-part short course is available for free via the Form website, covering key topics about the ketogenic diet, including how exactly it works, key benefits and criticisms, and what the future of keto looks like.
Dr Adam Collins PhD is Form’s head of nutrition and director of the MSc Nutrition course at the University of Surrey.