At week 56 , patients in the liraglutide group had lost a mean of 8.47.3 kg of body weight , and those in the placebo group had lost a mean of 2.86.5 kg ( a difference of -5.6 kg ; 95 % confidence interval , -6.0 to -5.1 ; P < 0.001 , with last-observation-carried-forward imputation ) .