If i just eat healthy and do a few sports in the week will i loose weight?

im 14, all the responses i ask to 'how to loose fat fast' cause im like 7kgs overweight say teens dont have to do much just walking and healthy eating? is this right, is that all it takes to loose around 6 kgs in a few months?! i dot have much time and equiptment anyways i really want to be toned and slim but everyone says dont worry about it :( or if i run morning and night for a few weeks will that make it all happen faster?! will it be worth it if i do, help please do teens weight just fall off from eating cereal and salads and a bit of excercise, anyone done it this way :)? ta