I have a two year old tortoise going on three, i believe hes a male he has a concave under his belly. he is a little larger than the size of my hand and he seems to be very healthy. i feed him grass when i can, lettuce dandelion leaves, collard greens. i give him some tomatoes every now and then he seems to really like them and some fruit occasionally. he doesn't look or act unhealthy in any way but i have noticed every winter he starts acting weird. He is very active and always hungry. I let him outside often to eat grass and play he usually spends the whole day outside during the summer months. I live in Utah so it gets too cold for him to go out during the winter. so i keep him in a fairly large room and i have a sun lamp and a heater, it stays really warm in there.i give him warm baths three times a weeks and he constantly has food and water but every winter he just stops eating and usually sleeps all day. he will eat if i bath him and let him run around my house, but he still doesn't eat that much. i heard that tortoises hibernate but when i looked up to see if that was the case i found that sulcatas did not do that. I'm very concerned about him because i want to make sure hes healthy and getting what he needs. what's wrong with him and what can i do for him?
There are a number of reasons why he may become lethargic during the winter. The most likely reason is that he's not set up correctly. First, you need to know what his temperatures are--"really warm" may mean that it's simply too hot for him. He needs a basking area of about 90 degrees, but he also needs a cooler area of about 75 degrees, and if the whole area is very warm he has no way of cooling himself off. This by itself will cause lethargy, so get a good digital thermometer and check the temps. Second, it doesn't sound like you have a UVB bulb for him. This isn't a sun lamp, but a special reptile bulb. Without it, he can't metabolize calcium properly. I would get a ZooMed Powersun, which provides heat and UVB in one bulb (replace every two years if you're only using it during the winter). Don't get any other brand of UVB bulb, because they are very unreliable; the Powersun, however, seems to have consistent output. It should be on for 12-14 hours a day. You also need to make sure that he has some moisture in his environment. You didn't say what kind of substrate you're using, but a mix of coir and playsand is good. Keep it a little damp so that the humidity is up higher. Basking lamps are very dehydrating, especially to smaller tortoises, and dehydration can lead to serious health problems (and lethargy).
Those are the most likely reasons as to why he's inactive and not eating.
Your tortoise is still too small to sex at this point. If he really is a male, you'll know, but it'll be a while longer yet. Sulcata are primarily grass/hay eaters, so I would work on getting him to eat more hay (it will be cheaper when he's bigger, too). Dandelion, turnip, mustard, collards, kale, etc. are all good greens as well, but grass and hay should be the main portion of the diet. Lettuce should be limited because it's lower in nutrition and fiber, and tomatoes, veggies, and fruit should all be avoided.
He will be too big to stay in the house before you know it, so it would be a good idea to have a plan in place for future outdoor accommodations. Because you have a fairly long, cold winter, he'll require a good sized shed so he can get some exercise. A 100+ lb. sulcata that's in a small space for months will be very unhappy and destructive. He'll have the same requirements I outlined above--basking temperature, UVB, and humidity--so it'll take some planning to put it all together. Good luck, and if you have further questions please ask!