Abstract
Background. Short-term interventions based on very low-calorie ketogenic diets (VLCKDs) and meal replacements may be prescribed to selected overweight or obese patients. Few, inconsistent data are available on protein intake from various sources on body weight, composition of gut microbiota and metabolic outcomes in these patients. Aim. To compare efficacy, safety and effect on microbiota composition of short-term isocaloric very low-calorie ketogenic diets encompassing whey, vegetable or animal proteins, in obese patients with insulin resistance. Materials and Methods. 48 obese patients (19 males and 29 females) with HOMA-index ≥ 2.5, age mean: 55.2 years (range: 45-73), BMI mean 35.9 kg/m2 (range: 30.2 - 46.4) were randomly assigned to three isocaloric VLCKD regimens (≤800 kcal/day) containing either whey, plant or animal proteins for 45 days, with assessments of anthropometric indexes, blood and urine chemistry, body composition, muscle strength, taxonomic composition of the gut microbiome. Results. A significant reduction of body weight, BMI, blood pressure, waist circumference, HOMA index, insulin, total and LDL cholesterol was observed in all the patients, regardless the dietary protein source. Patients fed with whey proteins and vegetable proteins had a more pronounced decrease of visceral adipose tissue (VAT) compared with the group fed with animal proteins. The markers of renal function slightly worsened in the group fed with animal proteins. A decrease in relative abundance of Firmicutes and an increase of Bacteroidetes was observed after VLCKDs. This pattern was less pronounced in patients consuming animal proteins. Conclusions. VLCKDs lead to significant weight loss and a striking improvement of the metabolic parameters over a short period of time. VLCKDs based on whey or vegetable proteins induce a larger reduction of VAT, have a safer profile and determine a healthier microbiota composition compared to those containing animal proteins.