My weight that i want to lose. Doctor told me to stop eating white bread, long loafs and sugar

Hey, i'm 14 years old, turning 15 this week. When i was younger i was bigger than other kids, i had more weight. Now my height is about 172cm and i weight 178 pounds. I visited a doctor before summer, and he told me to stop eating white bread, long loafs ( found it in google translate) and sugar. I haven't been eating those from the time he told me to stop. I'm only eating black bread now and only putting less than one tea spoon of sugar when drinking tea. My legs got a bit thiner but my upper part looks like it stays the same. And also i have to walk like 3 kilometers from school home everyday. So that also helps i guess. Maybe any of you could say what i can do better? Thanks!