Hi and welcome to the boards.
Gyne cant be totally reduced with exercises or diets. The only way to totally get rid off gynecomastia is via surgery. Some males are lucky and their gyne goes away after puberty but a great amount of these males never lose their gyne. I think losing weight and exercising can reduce a small amount of fat on the chest but that difference is almost 5%. My brother lost lots of weight, did push up, bench press and other weight exercises and was able to lose some fat on the top of his chest. I also did lots of chest exercises and was able to lose fat on the top of the chest but the fat remained on the bottom, around the nipples.
Working out and lifting weights to increase your chest muscles will also make your gyne look worse because the muscle underneath the fat and gland develops and pushes the gyne out even more. After surgery the results are much better for those who have muscle under their fat and gland, since then you are left with a muscular chest.
