Diet is a small part. Once you get into a regular workout routine if you are putting on muscle and taking away fat your metabolism will increase. In my personal experience I actually gained weight the first month and a half or so that I was seeing a personal trainer then at one point I hit the peak and then the weight began to come off very quickly. I lost 25lbs in about 3-4 months. Throughout all of this my trainer had me eating 4 times a day, a good breakfast consisting of eggs, bacon or whatever protein you want and some fruit, a light lunch such as half a turkey sandwich and small salad, a mid afternoon meal consisting of the rest of the sandwich and some other snacky stuff and then a portion correct dinner in the evening. Dieting alone can actually put weight on your body as it will go into "starvation" mode when it realizes it isn't getting the calories that it needs and will start packing away energy as fat, when you eat regularly and exercise your body will not do this.