I'm 11 and weigh around 48 Kg and am around 164cm. Am I too heavy because my friends whoare all at least 10cm shorter than me all weigh only around 38kg.

Your weight sounds absolutley perfect for your height. Just keep eating healthy. You are still growing, your height and weight will eventually balance out.

So, no you are not too heavy, you are just right.

You right at the beginning of your growing stage, you are just fine, just eat healthy foods, fruits and stay away from junk food. :p