Sounds like a growth spurt to me. Especially if it just started.
My 16 yr old eats very often, always has. She has always been a grazer...extremely health conscious, very athletic, girly girl......not an ounce of fat on her body, works out at least 1-2 hrs a day with her cheer squad , on her own and private cheer trainer (weekly).
Like you, I was concerned but my pedi reassured me that grazing is perfectly fine as long as she is making healthy choices. I make sure that I provide healthy choices for her. She takes low fat granola bars, raisins, dried fruit and water to school. Her breakfast is a bowl of cereal or oatmeal with a piece of toast and papaya juice. She eats a lot of whole wheat pasta and I keep home made marinara on hand. This kid will choose an apple or fruit over some candy or chips any day. I am VERY lucky to have such a healthy eater.
When she comes hom from school, usually 5:30-6, she will eat fruit. She loves diced fresh peaches, nectarines, plums, strawberries and blueberries. I toss them with a bit of lemon juice and touch of sugar.
We go through a LOT of water. We each drink at least 6-8 of the 16 oz bottles a day. Neither of use are much on soda, at most one a week which is Sprite or 7Up.
Think about the serving sizes you get at restaurants. The portions are so huge. I love a good greasy cheeseburger now and then but I cannot eat an entire burger. When I go out to eat, I always bring at least 1/2 home and eat it later. She does this too.
Maybe this helps you in some way.