I know the water works because someone I went to high school with said she lost 5 pounds just from switching to water alone. But I agree that it probably doesn't work for everybody. But yeah it also flushes out fat and its not carbinated which also contributes to weight gain.
Breakfast is also important in weight control. High fiber is good for someone with diabetes as long as you eat foods with low sugars and it curves appetite. There are high fiber cerals out there that you can eat. Eggs is one of the best sources for protein so those are good to have. Just stay away from your fatty foods, like sausages and bacon.
Heres an article that better explains the importance of breakfast.
http://news.bbc.co.uk/1/hi/health/2824987.stm
Also I hear if you do good cardio in the mornings, you burn 3x more fat than if you workout in the evenings. Plus you got to stay consistant with your workouts and not skip a lot of days. 3-5 times a week is best. Depends in your intensity level. Hopefully that will shed some light.