If by “getting in shape” you mean building muscle, as mentioned, the only way to build significant muscle mass is to work the muscle with resistance training. Resistance training breaks down the muscle to the point where muscle repair and adaption is necessary. The muscles grow during the rest period when they are rebuilding and adapting. Protein and protein supplements provide the amino acids which are the building blocks for muscles.
If you increase your food intake without training your muscles with resistance training, you might be able to burn off the excess calories with exercise and activity, but you will not necessarily increase muscle mass. If you do not increase your activity to match, you may end up putting on a nice layer of fat.