Is your daughter sneaking food because she's hungry? As in, does she say all the time that her tummy hurts and she's hungry? Starving? Sits down to eat with you at lunch or supper time but then needs to constantly eat in between snacks?
My daughter was like that. She didn't sneak food, but she was hungry ALL THE TIME. Literally, she'd eat all day long. My husband and I were at our wits end, trying to figure out why she would need to eat and eat and eat.
Then, four years ago (when she was 7 years old), I became sick and started using alternative medicine. I changed the way the entire family eats. I threw out all processed food and put organic food in its place. We put a reverse-osmosis system on our kitchen water line. We threw out the aluminum pots and pans and now cook with cast-iron. I had gotten tested for food allergies/intolerances; I got my hubby and daughter tested as well. We all have varying degrees of gluten intolerance (that means, can't eat anything with wheat, barley, or rye, spelt, triticale, farima, durum, etc.). My husband and I are allergic to casein (means no cow products) and soy. I also have intolerances to 20 other foods. My daughter, on a daily basis, does not get any products with soy, cow milk products, or wheat in our house. If there was an issue with inflammation because of a food item that my daugher's body didn't like, well, by not eating these items, it's helped her.
Once we shifted from eating processed food to making our own out of fresh, organic food (to include grass-fed meat/no antibiotics/no hormones/PURE), my daughter's obsessive need to eat, eat, eat! went away!! OMG, she was finally FULL after she ate. It took about a month before we didn't hear her complain about being hungry, but now, she only says it when she has a growth spurt.
My daughter is built big, like my husband. She'll never be a skinny minny. But she was on course to being very, very obese if we didn't do something to help her. She has stayed pretty much at the same weight now for the last three years but has shot up about four to five inches in height. The last time I had her in for a physical, her doctor was very happy that we've managed to keep her at the weight she's currently at. He sees no issues with her weight anymore, because he feels that her growth in height will cancel out any problems/issues with her weight.
What does your daughter eat? Hotdogs, potato chips, ding dongs, Cheetos? Does she drink diet pop or chew gum (both have Excitotoxins in them; aspartame in the pop, artificial sweeteners in the gum. Cheetos now has MSG in their ingredients, another excitotoxin)? Do you buy store bought white enriched bread? Eat white rice? Both of them have been so refined, it's like literally not eating any food; there is nothing left there for your body to absorb. Oh sure, the government will tell you that it's been "fortified." Fortified with synthetic vitamins and minerals is NOT the same thing as getting everything your body needs from real food.
Processed foods are "manufacturered food;" that means, they are "made" foods from combining chemicals and such to look, taste, and appeal to the senses as if they are food--but they are merely empty and devoid of nutritional substance. But that doesn't mean they don't have calories! If you take in a lot of calories but you don't give your body any substance, like nutrition your body needs to grow and maintain itself (vitamins, minerals, enzymes, amino acids), then the body is always going to feel starved and is going to want and crave food. And if you don't give your body what it needs and wants--vitamins, minerals, enzymes, amino acids--then it's going to keep looking and looking for what it wants and needs. You can eat all the "food" you want, but if it's processed and has empty nutritional value, your body will never feel full.
Change the way your family eats, and I bet you'll see a change in your daughter. One thing I learned when I discovered I had food allergies and intolerances is that a person will CRAVE the food they are intolerant/allergic to. I love artisian breads; absolutely love European hard breads--Panera Bread, I loved you!! Loved eating bread when I was in Europe. I could easily have bread as my only course for supper. Then I discovered I have a severe intolerance to bread. Even when bread was making me sick, my body kept craving it over and over and over--like a junkie. Now that I don't eat gluten, I in fact rarely ever eat bread anymore, even gluten-free bread. Why? Because my body no longer gets what it craves/wants but cannot have.
That would be another avenue you should look into. Take your daughter to a Naturopathic doctor and have her tested for food allergies and intolerances. I can almost guarantee that if she is foun to have food allergies and food intolerances and she QUITS eating them, her hunger will go away. But only if you also change what she's eating--or not eating.
Good health means a healthy body; Healthy food means a healthy body. A healthy body means no illness and no doctor visits, no pharma drugs.
Good luck.