Losing weight has many advantages, but also some side effects. The skin on the body takes the shape of the internal organs, muscles and the rest of what it is made up of. So as the body fat begins to reduce, the skin has nothing to hold onto and it begins to hang. One solution to this is to train the muscles so that they become stronger and the skin wraps itself around it.
So any resistance, strength training or yoga specifically aimed at the muscles will benefit you. Muscles weigh more than fat, but take up less space. So, as they get stronger the skin binds itself around it and gets tighter. But this process takes time, so do have patience. Remember, the goal of exercise should ideally be getting fitter, not only just losing weight.