A recent study from the University of Bath has found that the ketogenic diet, while effective for fat loss, can lead to increased cholesterol levels and a reduction in beneficial gut bacteria. The research, published in Cell Reports Medicine, involved 53 healthy adults over a 12-week period.
Key Takeaways
- Increased Cholesterol: The keto diet raised cholesterol levels, particularly in small and medium-sized LDL particles. The diet also increased apolipoprotein B (apoB), which can cause plaque buildup in arteries.
- Reduced Beneficial Gut Bacteria: The keto diet altered gut microbiome composition, notably decreasing Bifidobacteria, beneficial bacteria often found in probiotics. This bacteria has wide-ranging benefits, including producing B vitamins, inhibiting pathogens, and lowering cholesterol.
- Glucose Tolerance: The keto diet reduced glucose tolerance, meaning the participants’ bodies became less efficient at handling carbohydrates.
- Fat Loss: Both the keto and low-sugar diets resulted in fat loss. The keto diet led to an average of 2.9 kg fat mass loss per person, while the low-sugar diet resulted in an average of 2.1 kg fat mass loss per person over 12 weeks.
- Metabolism: The keto diet caused significant changes in lipid metabolism and muscle energy use, shifting the body’s fuel preference from glucose to fats.
- Physical Activity Levels: Both diets achieved fat loss without changing physical activity levels.
Study Details
The study involved participants following either a moderate sugar diet (control), a low-sugar diet (less than 5% of calories from sugar), or a ketogenic low-carbohydrate diet (less than 8% of calories from carbohydrates). Researchers found that the keto diet raised cholesterol levels, particularly in small and medium-sized LDL particles, and increased apolipoprotein B (apoB), which can cause plaque buildup in arteries. In contrast, the low-sugar diet significantly reduced cholesterol in LDL particles.
Impact on Gut Health
The keto diet also altered gut microbiome composition, notably decreasing Bifidobacteria, beneficial bacteria often found in probiotics. This bacteria has wide-ranging benefits, including producing B vitamins, inhibiting pathogens, and lowering cholesterol. Sugar restriction did not significantly impact the gut microbiome composition.
Glucose Tolerance and Metabolism
The keto diet reduced glucose tolerance, meaning the participants’ bodies became less efficient at handling carbohydrates. Researchers also noticed that the keto diet caused significant changes in lipid metabolism and muscle energy use, shifting the body’s fuel preference from glucose to fats.
Physical Activity and Fat Loss
Both the keto and low-sugar diets resulted in fat loss without changing physical activity levels. The keto diet led to an average of 2.9 kg fat mass loss per person, while the low-sugar diet resulted in an average of 2.1 kg fat mass loss per person over 12 weeks.
Expert Opinions
Lead researcher Dr. Aaron Hengist highlighted the concerning cholesterol findings, stating that the ketogenic diet increased the levels of unfavorable fats in the blood, which could have long-term health implications such as an increased risk of heart disease and stroke.
Dr. Russell Davies, who led the microbiome research, explained that dietary fiber is essential for the survival of beneficial gut bacteria like Bifidobacteria. The ketogenic diet reduced fiber 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, intestinal infections, and weakened immune function.
Professor Javier Gonzalez, who oversaw the research, commented on the glucose findings, noting that the ketogenic diet reduced fasting glucose levels but also reduced the body’s ability to handle carbs from a meal. This could increase the risk of developing type 2 diabetes in the long term if these changes persist when people switch back to a higher carbohydrate diet.
Conclusion
In light of this new research, the academics conclude that a low-sugar diet may be better for most people. More work is needed to understand how individuals may benefit from each type of diet. The government recommends that free sugars should be restricted to less than 5% of total energy intake. The ketogenic diet is effective for fat loss but comes with varied metabolic and microbiome effects that may not suit everyone.
Sources
- Ketogenic Diet reduces friendly gut bacteria and raises cholesterol levels, University of Bath.
- Keto diet study shows increased LDL cholesterol, higher apolipoprotein B and reduced gut bacteria, Medical Xpress.
New research reveals keto diet’s impact on cholesterol and gut microbiome
, News-Medical.- Keto diet helps with weight loss but also raises cholesterol levels | New Scientist, New Scientist.
- Keto Diet Raises Cholesterol and Reduces Beneficial Gut Bacteria | Technology Networks, Technology Networks.