What Causes Excessive Weight Gain And Red Spots On The Face?

My 7 year old granddaughter has gained a lot of weight over the past year. Her face is constantly red and has bumps on it. She is going to the bathroom every 10 to 15 minutes, sometimes even 2 0r 3 minutes apart. She gets up several times during the night to urinate. She is a much much taller than anyone in her age group . I would estimate her weight to be close to 90 lbs. She started putting on weight about a year ago. There has not been a change in her diet. She eats healthy but is hungry all the time.