Thirty-eight overweight participants ( 16 women , 22 men ; average body mass index : 29 kg/m , mean age 52.8 years ) were randomized into two diet groups : a very low kcal diet group ( VLCD ; 600 kcal/day , n = 21 ) and a low kcal diet group ( LCD ; 1,200 kcal/day , n = 17 ) .