Power calculation
Sample size calculation for this three-armed placebo-controlled study is performed in STATA software based on alpha = 0.0500 and power = 0.8000. Estimated change in body weight; Mean change in the placebo group = 0.00 kg, Mean change in single dose probiotic group = − 2.00 kg, Mean change in double dose probiotic group = − 4.00 kg. A within-group variance of 18.3 was anticipated. Depending on the estimated standard division within each group, 20–24 participants are needed per group, which means a total number of 60–72. We assumed a dropout rate of about 4–6 participants per group and therefore aimed to include 75–90 participants in total for randomization.