Nowadays we have to be as much active as we could. And we have to eat healthy food because it's gonna (не знаю если в школе можно использовать "gonna", так как это американизированный вариант, поэтому можешь написать going to) help us to keep our bodies in a great shape. Also, eating healthy food has an impact on your mind, physical activity and mental operability (работоспособность). You are not supposed to eat healthy food jyst when you are on a diet and you want to lose weight. But it should be for your lifestyle. It's not very hard, but you just need to adjust to it.