A TRENDY diet destroys ‘friendly’ gut bacteria while raising the risk of a silent killer condition that can make you vulnerable to heart attacks, scientists say.
Loved by Kim and Kourtney Kardashian, ketogenic diets – better known as ‘keto’ – involve upping your protein intake while cutting down on carbs.
Kim reportedly used the diet – hailed as a weight loss wonder – to shed a whopping 60 pounds after having her son Saint.
Her sister Kourtney also revealed her doctor put her on the diet to help her detox, adding: “My body never looked better than when I did the keto diet.”
Researchers at the University of Bath said switching to a ketogenic eating plan can indeed result in fat loss.
But keto diet followers could be saddled with a host of additional side effects, they warned.
Asking healthy adults to cut down on carbs for up to twelve weeks, they found that keto diets raised cholesterol levels and reduced number of beneficial bacteria in people’s guts.
Cholesterol is a fatty substance that’s produced by your liver and also collects in the blood from the food you eat.
Having to much of it in your blood is referred to as ‘high cholesterol‘ and it can increase your risk of having a heart attack or stroke if you can’t lower it.
Lead researcher Dr Aaron Hengist commented on the study’s findings on cholesterol.
“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,” he said.
By allowing only very low amounts of carbohydrates, the keto diet aims to o send the body into a state of ‘ketosis’ where it relies on a different type of fuel.
Instead of relying on sugar that comes from carbs – such as grains, legumes, vegetables, and fruits – the keto diet relies on ketone bodies, which liver produces from stored fat.
Burning fat seems like an ideal way to shed weight, but getting the liver to make ketone bodies can involve eating fewer than 20 to 50 grams of carbs per day, according to Harvard Health.
For reference, a medium-sized banana has about 27 grams of carbs.
Published in Cell Reports Medicine, the research followed 53 healthy adults for up to 12 weeks, as they followed either a moderate sugar diet, a low-sugar diet or a low-carb keto diet that involved getting less than 8 per cent of their calories from carbohydrates.
Both the keto and low-sugar diets resulted in fat loss – about 2.9 kg 2.1 kg per person respectively.
But Bath researchers found that the keto diet raised participants’ cholesterol levels – especially compared to the low-sugar diet, which significantly reduced them.
The keto diet also altered participants’ gut microbiome composition, notably decreasing beneficial bacteria called Bifidobacteria often found in probiotics.
According to the study authors, this bacteria can inhibit pathogens and harmful bacteria while lowering cholesterol.
“Dietary fibre is essential for the survival of beneficial gut bacteria like Bifidobacteria,” according to Dr Russell Davies, who was in charge of the gut health portion of the study.
“The ketogenic diet reduced fibre intake to around 15 grams per day, half the NHS recommended intake.
“This reduction in Bifidobacteria might contribute to significant long-term health consequences such as an increased risk of digestive disorders like irritable bowel disease, increased risk of intestinal infection and a weakened immune function.”
In contrast, the low sugar diet had no significant impact on gut microbiome composition.
The US Wold and News Report ranks the best, science-backed diets across the world that work on a yearly basis.
Its panel of medical and nutrition experts, specialising in diabetes, heart health and weight loss evaluate different diet plans’ health risks and benefits, long-term sustainability and evidence-based effectiveness.
Year after year, the Mediterranean ranks first as the ultimate choice for healthy eating.
“It is one of the most well-researched diets that has been proven to reduce the risk of heart disease, improve brain and mental health and decrease inflammation,” experts said.
The diet has been on its winning streak for seven years in a row, after panelists gave it top spot in January 2024.
It emphasises eating whole, unprocessed foods, healthy fats, and plenty of plants, with ingredients like olive oil, whole grains, beans, seafood, leafy greens, and other veggies.
These were the top five diets of 2024, according to rankings from the US News & World Report:
Source: US News & World Report
Finally, researchers found that the keto diet reduced glucose tolerance, meaning participants’ bodies became less efficient at handling carbohydrates.
Professor Javier Gonzalez said this response may indicate that people could be more at risk of developing type 2 diabetes after coming off a keto diet.
“The ketogenic diet reduced fasting glucose levels but also reduced the body’s ability to handle carbs from a meal,” he explained.
“By measuring proteins in muscle samples taken from participants’ legs, we think this is probably an adaptive response to eating less carbohydrates day-to-day and reflects insulin resistance to storing carbs in muscle.
“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.”
The authors concluded their study by saying while further research is needed on each diet to know how people might benefit from them, if people want to lose weight, they would recommend a low sugar intake one.
Dylan Thompson, who also oversaw the work, said: “The ketogenic diet is effective for fat loss, but it comes with varied metabolic and microbiome effects that may not suit everyone.
“In contrast, sugar restriction supports government guidelines for reducing free sugar intake, promoting fat loss without apparent negative health impacts.”
The government recommends that free sugars – added to food or drink or found naturally in honey, syrups, fruit juices and smoothies – should be restricted to less than 5 per cent of total energy intake.
That amounts to about 30g of sugar a day.
