A new study published in the journal Metabolites has found that a very-low-calorie ketogenic diet (VLCKD) offers stronger short-term improvements in weight loss, blood sugar control, and gut microbiota composition than a Mediterranean diet (MD) in people recently diagnosed with type 2 diabetes and obesity.
Background
Type 2 diabetes is a common long-term illness, often linked to obesity, especially around the abdomen. It occurs when the body’s ability to produce or use insulin is impaired, leading to high blood sugar and inflammation. This can result in serious health problems such as heart disease and kidney damage.
Factors like genetics, inactivity, and poor diet—especially one high in processed sugar and low in fruits and vegetables—can increase the risk of type 2 diabetes. Recent research also points to the gut microbiome, the community of microorganisms in the digestive tract, as a key factor in managing metabolism. These microbes can affect inflammation, insulin sensitivity, and other vital processes.
While the Mediterranean diet is already known to benefit heart and metabolic health, less is known about how VLCKDs affect the gut microbiome over time. This study also looked at whether VLCKDs can be sustained and how they compare with the MD over 12 months.
Study Design
The research followed 11 newly diagnosed diabetic patients, aged 45–65, over one year. Eight of them completed the full study. None had started medication before the trial began.
Participants were randomly assigned to either a VLCKD or a low-calorie MD. Those on the ketogenic diet started with protein shakes and strict carb limits (under 30 grams per day) for the first two months. They then transitioned to the MD by the fourth month. The MD group focused on plant-based foods, moderate protein intake, and balanced macronutrients from the start.
From month four onward, all participants followed the MD.
Researchers assessed changes in body weight, BMI, waist size, fat and lean mass, fasting blood sugar, and cholesterol. They also analyzed the gut microbiome by sequencing stool samples. Physical activity and diet adherence were tracked through questionnaires and food diaries.
Key Findings
Both diets helped improve weight and blood sugar control, but the VLCKD showed stronger results by the six-month mark. People on the ketogenic diet lost more weight and had greater reductions in blood sugar levels (HbA1c) and waist size. Specifically, BMI dropped by 5.8 kg/m² (p = 0.006), and HbA1c levels dropped by 1.2% (p = 0.02).
The VLCKD group also saw an increase in beneficial gut bacteria like Akkermansia, which is known to support gut health. However, this benefit declined by the end of the 12-month period. While the number of different gut bacteria species (alpha diversity) stayed about the same, there were noticeable changes in the types of bacteria (beta diversity), especially during the ketogenic phase.
In contrast, the MD group saw fewer changes in gut bacteria and less improvement in blood sugar and weight. Although both diets helped lower fasting glucose and triglyceride levels, the VLCKD had more pronounced short-term effects.
Conclusions
The study suggests that VLCKDs may offer stronger short-term health benefits than the MD for people with type 2 diabetes and obesity. However, some of these benefits faded after switching to the MD later in the trial.
The researchers caution that while ketogenic diets can be effective, they also come with potential risks like loss of muscle mass and higher cholesterol levels. They recommend that such diets be used under medical supervision.
Overall, combining the metabolic benefits of the ketogenic diet with the sustainability of the Mediterranean diet could be a promising approach. But more long-term studies are needed to confirm these findings and to help develop effective, personalized diet plans for people with diabetes.
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