The ketogenic diet, or keto diet, has become a household name, thanks to celebrity endorsements and promises of effortless weight loss by cutting out carbohydrates from our diet.
While it may help shed a few kilos, new research published in the Cell Reports Medicine, suggests that this controversial diet could have serious downsides, including an increased risk of heart attacks and type-2 diabetes.
“The ketogenic diet is effective for fat loss, but it comes with varied metabolic and microbiome effects that may not suit everyone,” said Professor Dylan Thompson, who led the study at the University of Bath.
But first, what is a Keto diet?
The ketogenic diet, commonly known as the keto diet, is a high-fat, low-carbohydrate regimen designed to push the body into a state of ketosis.
Ketosis is a metabolic condition where in the absence of its primary fuel source—carbohydrates—the body starts burning stored fat for energy.
A keto diet consists of 75 per cent fat, 20 per cent protein and only 5 per cent carbohydrates. This drastic dietary shift means cutting out bread, pasta, rice, starchy vegetables like corn, beans, and squash, and almost all fruits. Instead, people on the keto diet consume meats, low-carb vegetables such as cauliflower and broccoli, dairy, nuts, and seeds.
In a typical diet, carbohydrates are broken down into glucose, which serves as the primary energy source for the body. However, when following the keto diet, carbohydrate intake is drastically reduced, typically to less than 50 grams per day. This forces the body to deplete its glycogen stores and switch to burning fat for fuel, producing ketones in the process. These ketones then become an alternative energy source for the brain and other organs.
The weight loss benefits of this diet have made it popular, with many celebrities like Gwyneth Paltrow, Jennifer Aniston, Halle Berry, and Kourtney Kardashian endorsing it. However, while the keto diet may help shed pounds, recent research highlights significant potential downsides.
What does the study say?
The study involved 53 healthy adults, with an average age of 34 who were assigned to a moderate sugar diet or a low sugar diet (less than 5 per cent of calories from sugar), or a keto diet (less than 8 per cent of calories from carbohydrates).
Researchers then measured aspects like weight loss and other health indicators four weeks into the study and again at the study’s conclusion of 12 weeks.
Analysing the results, scientists found people on the keto diet lost only slightly more weight, shedding just over 2.9 kg. While those cutting sugar from their diet lost about 2.1kg. However, those on the keto diet also had a range of concerning health indicators.
Increased cholesterol
Experts found participants who had cut carbs had raised bad cholesterol levels, including a specific type (apolipoprotein B), which is linked to dangerous plaque buildup in the arteries that could lead to heart problems.
Lead researcher Dr Aaron Hengist emphasised the alarming cholesterol findings and said, “Despite reducing fat mass, the ketogenic diet increased the levels of unfavourable fats in the blood of our participants, which, if sustained over years, could have long-term health implications such as increased risk of heart disease and stroke.”
On the other hand, the study revealed that a low-sugar diet effectively lowered the amount of bad cholesterol in participants’ blood.
Reduced favourable gut bacteria
A separate examination of participants’ gut microbiome—the collection of microscopic organisms in the digestive system—revealed that those on a keto diet had reduced levels of Bifidobacteria.
This beneficial bacteria, commonly found in probiotic treatments, helps produce B vitamins, prevents harmful bacteria from taking hold in the gut, and lowers cholesterol.
Dr Russell Davies, who led the microbiome research, explained the impact on gut health, “Dietary fibre is essential for the survival of beneficial gut bacteria like Bifidobacteria. The ketogenic diet reduced fibre intake to around 15 grams per day, half the NHS-recommended intake.”
He further said that the reduction in Bifidobacteria might lead to significant long-term health problems such as an increased risk of digestive disorders such as irritable bowel disease, an increased risk of intestinal infection, and a weakened immune function.
Again, in contrast, the study found a low-sugar diet to have no significant impact on gut microbiome composition.
Insulin resistance
The study revealed that participants on a keto diet showed signs of insulin resistance, as their bodies struggled to manage carbohydrates effectively. This adaptation could lead to an increased risk of developing type 2 diabetes if they return to a normal diet.
“The ketogenic diet reduced fasting glucose levels but also reduced the body’s ability to handle carbs from a meal,” said Professor Javier Gonzalez, another expert in nutrition, exercise, and metabolism.
“This insulin resistance is not necessarily a bad thing if people are following a ketogenic diet, but if these changes persist when people switch back to a higher carbohydrate diet it could increase the risk of developing type 2 diabetes in the long-term,” he added.
As the popularity of the keto diet continues to rise, it is crucial for individuals to weigh these risks against the benefits and consider a more balanced approach to weight loss and health.
With input from agencies
