It’s the low-carb diet promoted by celebrities that promises you can effortlessly lose weight by simply cutting out foods like potatoes, pasta and bread.
While the controversial keto diet can help you shed a few pounds, it can also have serious downsides, including an increased risk of heart attacks.
According to research from the University of Bath, people who followed the diet had higher cholesterol levels and lower levels of ‘friendly’ gut bacteria.
These effects occurred after just three months of the diet. And what’s worse, people on the keto diet didn’t lose more weight than people on a less drastic, low-sugar diet.
Experts warn that people who follow a ketogenic diet could harm their health in the long term.
An example of a range of ketogenic foods. A recent study in the UK found that while a keto diet can help you lose weight, it can come at a high price that harms your long-term health.
The goal of a keto diet is to put people into a state called ketosis by eliminating virtually all energy-rich carbohydrates.
That means no bread, pasta, rice, no starchy vegetables like corn, beans and squash and almost no fruit.
Without carbohydrates, the body will burn stored fat for energy, allowing people to lose weight.
In the most recent study, experts took 53 healthy adults and randomly assigned them to three diets.
One of these was a low-carb ketogenic diet, and another was a low-sugar diet, which was also intended to help people lose weight.
The final diet assessed was a “moderate sugar diet” designed to mimic the average food consumption of people in high-income countries such as Britain. Britain served as a control for the experiment.
The researchers then measured aspects such as weight loss and other health indicators four weeks into the study, and again at the end of the study after twelve weeks.
When scientists analyzed the results, they found that people who followed the keto diet lost only slightly more weight: just over 6.4 pounds (2.9 kg).
Those who stopped eating sugar lost about 2.1 kg.
However, people following the keto diet also had some concerning health indicators.
Experts found that participants who ate fewer carbohydrates had higher levels of bad cholesterol, including a specific type linked to dangerous plaque buildup in the arteries.
In contrast, a low-sugar diet lowered the amount of bad cholesterol in the blood.
Additionally, separate research into the gut microbiome (the collection of microscopic organisms in the digestive tract) found that participants following a keto diet had lower levels of Bifidobacteria bacteria.
Often found in probiotic treatments, this bacteria helps produce B vitamins, prevents harmful bacteria from building up in the gut, and also lowers cholesterol.
In contrast, the low-sugar diet had no significant impact on the composition of the gut microbiome.
Finally, people who followed a ketogenic diet also showed signs of insulin resistance, because their bodies forgot how to deal with carbohydrates. So when they switched back to a normal diet, they were at a higher risk of developing type 2 diabetes.
Actress Gwyneth Paltrow has previously advocated the keto diet as a way to improve health. She is pictured here in June of this year
Jennifer Aniston has been a fan of cutting out carbs in the past, but has since said she eats them in moderation. She is pictured here in February earlier this year
Lead researcher Dr Aaron Hengist, an expert in nutrition, exercise and metabolism, said the results show that weight loss is not the only health measure to consider when following a weight-loss diet.
“Despite reducing fat mass, the ketogenic diet caused an increase in the amount of unfavorable fats in the blood of our participants. If this continues over many years, it could have long-term health consequences, such as an increased risk of heart disease and stroke,” he said.
Dr Russell Davies, an expert in the gut microbiome and leader of this part of the research, added: ‘Dietary fibre is essential for the survival of beneficial gut bacteria such as Bifidobacteria.
‘On the ketogenic diet, fibre intake was reduced to around 15 grams per day, half the NHS recommended intake.
‘This reduction in Bifidobacteria can have significant long-term health consequences, such as an increased risk of digestive disorders such as irritable bowel syndrome, an increased risk of intestinal infections and a weakened immune system.’
Professor Javier Gonzalez, another expert in nutrition, exercise and metabolism, said increased insulin resistance among keto diet followers is also a potential health risk for the future.
“The ketogenic diet lowered fasting glucose levels, but also reduced the body’s ability to process carbohydrates from a meal,” he said.
‘This insulin resistance isn’t necessarily bad when people are on 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.’
The authors concluded their study by saying that more research is needed on these types of diets at this time. However, if people want to lose weight, they recommend a low-sugar diet.
Co-author Professor Dylan Thompson, an expert in human physiology, said: ‘The ketogenic diet is effective for fat loss, but it has diverse metabolic and microbiome effects that may not be suitable for everyone.
‘In contrast, limiting sugar supports government guidelines to reduce free sugar intake, which promotes fat loss without apparent negative health effects.’
Actress Halle Berry swears by the keto diet and has been following it for over 30 years to keep her type 1 diabetes under control. She is pictured here in April
Reality star Kourtney Kardashian also supported the diet and even shared her recipes online
Keto diets typically involve eating fewer carbohydrates, more fat, and a moderate amount of protein.
A ketogenic diet consists of 75 percent fat, 20 percent protein, and only 5 percent carbohydrates.
This differs radically from the NHS advice for a healthy, balanced diet, which advocates 30 percent fat, 15 percent protein and 55 percent carbohydrates.
The typical person following a ketogenic diet is advised to eat only 20 to 50 grams of carbohydrates per day.
A slice of whole wheat bread contains 14 grams of carbohydrates and a banana 20 grams. People who follow a ketogenic diet must therefore plan their meals carefully.
Despite several studies pointing to the potential dangers of the keto diet, it is becoming increasingly popular.
A number of celebrities, including Gwyneth Paltrow, Jennifer Aniston, Halle Berry and Kourtney Kardashian, have spoken out about following a low-carb diet in the past.