Background. Short-term interventions based on very low-calorie ketogenic diets (VLCKDs) and meal replacements may be prescribed to selected metabolic syndrome patients and/or to those with an altered microbiota composition. In this view, protein source choise is still debated. In fact, few and inconsistent data, are available on protein intake from various sources on body weight, composition of gut microbiota and metabolic outcomes in these patients.

Clinical case. A 52-year-old man affected by first degree obesity, hypertension, hyperuricemia, hyperinsulinism, hypercholesterolemia, hypertriglyceridemia and an altered gut microbiota with an increased Firmicutes/Bacteroidetes ratio, was admitted to our facility. Therefore, a diet therapy treatment with VLCKD (≤800 kcal/day) was set for a 45 days period based on meal replacements containing vegetal proteins. Anthropometric indexes, blood and urine chemistry, body composition, muscle strength and taxonomic composition of gut microbiota were assessed at the beginning and after 45 days. A significant reduction of body weight (109 vs 93,4 Kg), BMI (33 vs 27 Kg/m²⁾, blood pressure (150/100 vs 120/70 mmHg), waist circumference (114 vs 101 cm), HOMA index (9,1 vs 2,3), triglycerides (612 vs 129 mg/dl) , total cholesterol (318 vs 151 mg/dl) and HDL cholesterol (32 vs 48mg/dl) and visceral adipose tissue (793 vs 599 g) was observed at 0-45 days respectively. Moreover, a decrease in relative abundance of Firmicutes, an increase of Bacteroidetes and an increase of Verrucomicrobiae were also observed.

Conclusions. These preliminary results suggest that vegan VLCKD administrated to our patient led to a significant weight loss, a striking improvement of the metabolic parameters and a restoring eubiosis in gut microbiota. VLCKD with vegetal protein could be a good treatment for obesity leading to an improvement of metabolic syndrome also assisted by the rebalancing of gut microbiota.