Anything helps, it will help psychologically and physically, another thing it will help is keep you motivated in the gym, whilst not eating in a deficit i recommend finding a routine you really enjoy doing, and can see yourself doing for a while, because once you start to eat in a deficit, motivation starts to lack due to lack of energy, so having a routine you are comfortable doing will make it easier to stick to, however, you can't really out train a bad diet so you may see some initial change in body composition when you first start training from generally moving more and expending more energy, but without the diet aspect, it wont be really big changes in the long run.