What are ways you can naturally increase your metabolism and loose weight (not including exercise)?

I am about 15 pounds overweight and lost weight last summer but have gained it back. Is there any healthy ways you can make homemade supplements to increase metabolism or ways you can eat differently so small portions won't decrease metabolism? I will be continuing to exercise but I would like to see results faster and loose weight. I am still growing so I don't want anything harmful. Thanks so much :)