D.,
Like Jennifer's son, my 3 y/o boy is very very active. He doesn't walk ANYWHERE. He jumps or runs to get where he needs to go. He is non-stop from when he wakes up until when he goes to bed. I find it fun, personally.
As for candy, sweets, etc. We try to limit what we let him eat. He only gets candy when he goes on the potty (we are starting potty training). He doesn't get much juice, just milk and water. I'm not saying that we are over strict with the food, I know we could do better. I've been waivering on and off about going organic and such but haven't made the leap just yet. Snacks in our house consist of whole wheat crackers, 100% fruit chews, Cherrios (no sugar), and one or two cookies a day. We also let him have graham crackers because our younger son is eating them now.
TV, this is a tough topic and I'm more in the camp that controlled TV isn't the worst thing you can do for your kids. That being said, we haven't had the TV on in days. It's summer and we're always out doing something and letting Jacob run around and burn off some energy. We do let Jacob watch some TV on the weekends but to be honest, we've found that it's the only way to get him to sit still for even a short period of time. We'll put in a movie and he will sit for about 10 minutes and then he's up and running around. We'll just leave it on in the back ground and he'll return for his favorite parts of the movie. I wouldn't be comfortable if he was always wanting to watch it. If he started asking for it, I'd be redirecting to other activities.
Another thing that will get him to settle down is reading. He LOVES books and we read to him all the time. He's now starting to "read" to his younger brother (10 months). We've found that the pop-up books keep him interested and anything to do with counting or letters.
Finally, I will say that I have a friend that found out her VERY VERY active son had food allergies. If you find that the changes you make aren't working, that is something I would consider. She showed be video of before taking away his triggers and after. OMG, I was shocked. A whole different kid. I wouldn't have ever believed it if I didn't see it myself.
Good luck.
T.