Alterning Maintenance Diet to Increase Mass

Hi all,

I currently am following this diet for maintenance:

http://home.global.co.za/~lerner1/meals.xls

It is working very well, but I would like to slowly start adding mass. I emphasise slowly because I do not want to go on a full on bulk. As you can see I have carbs only in the morning, post workout and post post workout. I want to try and keep it this way. The main question I have is what I should be increasing in the diet. I know ultimately its calories which count, but I want to ask where I should fit in more calories? From carbs, fats, proteins? When in the day should I add them?

Any advice appreciated,
Thanks!