Physical activity and nutrition have a big impact on body composition as a whole. The amount you work out and what you put into your body can have negative or positive effects. For example, going to the gym frequently and eating a healthy diet will make for a healthy body. If someone were to eat all the junk in the world and not work out, they will more than likely end up gaining weight and that could have a negative effect. Overall, the relationship between the three is very dependent on one another and they very much impact each other making their relationship very codependent.