My sons chest measurement is 33 around he has armpit and chest fat how much more weight does he have to lose to get rid of the chest fat, he's 125-130 lb, and 15 yrs and 5'5 how much more weight to lose off the chest?

Well child visit: Schedule a well child visit with your son's PCP, he/she will provide you appropriate goals and lifestyle modification options. Depending on his overall health status; your son could benefit from healthy habits like regular physical activity and diet that is rich in non-starchy vegetable, lean protein and adequate water intake. Reduce processed food and sweetened beverage.

Chest fat: His weight is not the issue, he just needs to continue his development. I would suggest no diet in teenagers but choose healthy foods and try push ups, or weight lifting to build up his chest muscles.