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August 7, 2024 – Recent research published in Cell Reports Medicine has unveiled significant insights into the impact of ketogenic diets on health, highlighting both potential benefits and risks. The study, conducted by the Centre for Nutrition, Exercise, and Metabolism, involved 53 healthy adults over a period of up to 12 weeks, examining three dietary approaches: a moderate sugar diet (control), a low-sugar diet (with less than 5% of calories from sugar), and a ketogenic (keto) low-carbohydrate diet (with less than 8% of calories from carbohydrates).
Key Findings:
- Increased Cholesterol Levels: The ketogenic diet was found to raise cholesterol levels, particularly in small and medium-sized LDL particles. This diet also increased apolipoprotein B (apoB), a marker associated with plaque buildup in arteries. In contrast, the low-sugar diet led to a significant reduction in LDL cholesterol levels.
- Altered Gut Microbiome: Participants on the keto diet experienced a reduction in beneficial gut bacteria, specifically Bifidobacteria. This strain, often found in probiotics, plays a crucial role in producing B vitamins, inhibiting harmful bacteria, and lowering cholesterol. The sugar-restricted diet did not significantly affect gut microbiome composition.
- Reduced Glucose Tolerance: The ketogenic diet impaired glucose tolerance, indicating that participants’ bodies became less efficient at processing carbohydrates. Despite this, both the keto and low-sugar diets resulted in fat loss, with the keto diet achieving an average fat mass loss of 2.9 kg per person, compared to 2.1 kg with the sugar-restricted diet.
- Metabolic Changes: The study observed substantial shifts in lipid metabolism and muscle energy use in those on the keto diet, favoring fats over glucose. Both diets led to fat loss without altering physical activity levels.
Expert Opinions:
Lead researcher Dr. Aaron Hengist raised concerns about the keto diet’s impact on cholesterol levels:
“Despite reducing fat mass, the ketogenic diet increased levels of unfavourable fats in the blood, which could have long-term health implications, such as a higher risk of heart disease and stroke.”
Dr. Russell Davies, who focused on the microbiome, noted the impact on gut health:
“Dietary fibre is crucial for the survival of beneficial gut bacteria like Bifidobacteria. The ketogenic diet’s drastic reduction in fibre intake may contribute to significant long-term health issues, including digestive disorders and weakened immune function.”
Professor Javier Gonzalez commented on glucose tolerance:
“While the keto diet lowers fasting glucose levels, it also reduces the body’s ability to handle carbs efficiently. This insulin resistance might be an adaptive response to a low-carb diet but could pose risks if individuals switch back to a higher carbohydrate intake.”
Conclusion:
The researchers concluded that, based on current evidence, a low-sugar diet might be preferable for most people, aligning with government guidelines that recommend limiting free sugars to less than 5% of total energy intake. Professor Dylan Thompson summarized:
“The ketogenic diet is effective for fat loss but comes with varied metabolic and microbiome effects that may not suit everyone. In contrast, sugar restriction promotes fat loss while supporting overall health without apparent negative impacts.”
This study was supported by grants from The Rank Prize Funds, Cosun Nutrition Center, The University of Bath, and Ian Tarr, with additional support from the British Heart Foundation and Medical Research Council.
For more detailed insights, refer to the full study in Cell Reports Medicine.
