HELP! My hedgehog is gaining a dangerous amount of weight

Help my hedgehog, Fern, who is 2 1/2 has been gaining weight her whole life and she has now reached 805g. I’ve spent hundreds on vet visits now and each vet says that everything seems healthy and normal other than her weight. One vet told me to put her on mazuri and take her off cat food. I did that and she has gained 65g in 2 months. I feed her 1/2 tablespoon of food so I’m not over feeding her. Prior to that I had her on wholehearted Weight Control Grain Free Chicken and Pea cat food (32% protein 9-11% fat). Now I have been mixing the Mazuri and the cat food 1/2 tbs but she just keeps gaining weight. She runs on her wheel for like 30 seconds a few times an hour. I have a wheel and a saucer both in her cage and her cage is 16 square feet. So plenty of room to roam around. Please tell me exactly what foods to buy her and what to do. I’m so frustrated and desperate at this point.