With six meals a day you can pretty evenly spread your nutritional needs over the sixteen hours that you are awake for. This way there are no big spikes (in blood sugar) and your body (especially your muscles) are getting what they need all day long, bulking is 60% diet and 40% what you do in the gym, you can’t bulk without the right diet. When you have big meals you will have excess calories that will be turned into fat because of the limited ability of the ability to break down foods. For example the body can much better handle six meals with 600 calories in each meal than three meals with 1200 calories in each meal. It’s simple when you think about it.