BEIJING, May 22 -- Former 'Friends'star Jennifer Aniston is apparently so desperate to have a baby, that she has reportedly put beau Vince Vaughn on 'healthy' diet to increase her chances of conceiving.

    A friend of the couple revealed that they had changed their diet, and that Aniston was making Vaughn cut down on his love for drink, cigs and fast food.

    "Jen and Vince have changed their diets to prepare for a baby. She said to me 'We're both getting healthy - if Vince was drinking, smoking and eating burgers, my will power would be out the window," Femalefirst quoted the pal, as telling Britain's Grazia magazine.

    The friend also let out that the couple are reportedly planning to tie the knot later this year with a ceremony in Fiji, and that Aniston has been discussing wedding dresses with celebrity fashion designer Vera Wang.