A recent study published in Metabolites explored the effects of very-low-calorie ketogenic (VLCKD) and Mediterranean diets (MD) on the gut microbiota and metabolic health of newly diagnosed patients with type 2 diabetes and obesity (often referred to as diabesity). This investigation, conducted by researchers from Brazil and Italy, sheds light on how these diets affect microbial diversity, metabolic health, and anthropometric measures over a 12-month period.
Background
Type 2 diabetes mellitus (T2DM) is a prevalent chronic condition strongly associated with obesity, particularly visceral fat accumulation. T2DM is characterized by insulin resistance, elevated blood sugar, and inflammation, leading to various complications such as cardiovascular and renal diseases. Risk factors for T2DM include genetic predisposition, poor diet, sedentary behavior, and lack of fruits and vegetables in the diet. Recent research has highlighted the gut microbiota as an essential factor influencing metabolic health. The gut microbiome impacts immune function, inflammation, and insulin sensitivity, all of which contribute to metabolic outcomes.
While the Mediterranean diet has demonstrated cardiometabolic benefits, the long-term impact of VLCKD on the gut microbiota and metabolic outcomes remains under-explored. The current study investigates how these two diets affect individuals with diabesity.
The Study
The study followed 11 newly diagnosed patients with type 2 diabetes (aged 45-65), all of whom were initially untreated. Due to attrition, only 8 participants completed the full 12-month intervention. These individuals were randomly assigned to either the VLCKD or MD group. The VLCKD group started with protein-based meal replacements and less than 30g of carbohydrates per day for the first two months, transitioning to the MD protocol by the fourth month. The MD group emphasized plant-based foods, moderate protein intake, and balanced macronutrients.
Over the 12 months, the participants underwent regular assessments, including anthropometric evaluations (body weight, BMI, waist circumference) and metabolic tests (fasting glucose, cholesterol). The researchers also analyzed the gut microbiota using stool samples and genomic sequencing techniques.
Major Findings
Weight and Glycemic Control: The VLCKD group showed significant improvements in metabolic health compared to the MD group. After six months, the VLCKD group demonstrated reductions in BMI (−5.8 kg/m²) and HbA1c (−1.2%), both statistically significant. These changes were less pronounced in the MD group.
Gut Microbiota Shifts: The gut microbiota composition shifted considerably in the VLCKD group. The abundance of beneficial taxa, such as Akkermansia, known for its role in maintaining gut barrier integrity and supporting metabolic health, increased significantly during the ketogenic phase. However, by the 12-month mark, these beneficial taxa decreased, showing the transient nature of the microbial shifts caused by VLCKD.
Microbial Diversity: While the alpha diversity (species richness) remained stable across both diets, the beta diversity (community composition) revealed significant shifts in the VLCKD group. These shifts suggest that VLCKD may have more substantial impacts on the gut microbiome than the MD.
Muscle Mass and Cholesterol: The VLCKD group experienced notable reductions in fat mass, but these were accompanied by a reduction in fat-free mass, raising concerns about muscle preservation on the ketogenic diet. Additionally, there was a significant increase in LDL cholesterol levels in the VLCKD group by the 12-month mark, indicating potential long-term cardiovascular risks.
Impact of MD: While the MD group did show some improvements in anthropometric and metabolic measures (such as reduced fasting glucose and triglycerides), the microbial shifts were minimal compared to those in the VLCKD group. The improvements in the MD group were also less sustained over time.
Conclusions
The study concluded that VLCKD provided superior mid-term benefits in terms of metabolic health, weight management, and gut microbiota composition for patients with diabesity compared to the Mediterranean diet. However, these benefits were not sustained over time, with the beneficial microbial changes seen during the ketogenic phase gradually diminishing by the 12-month mark. Additionally, the increase in LDL cholesterol and reduction in muscle mass raised concerns about the potential long-term risks of VLCKD.
The researchers suggest that a combination of ketogenic and Mediterranean dietary principles could offer an effective, personalized strategy to optimize both metabolic and gut health. However, they also emphasize the need for long-term studies to validate these findings and explore sustainable dietary models for managing diabesity.
This study highlights the importance of considering both dietary interventions and the gut microbiome in managing type 2 diabetes and obesity. Further research will be necessary to determine the long-term efficacy and safety of these dietary approaches.
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