Interesting that things like inflammation, depression and stress are controlled by the body when it needs to save calories. This would be why fasting and exercise can have anti-inflammatory and mood lifting effects, not because those things are necessarily good for you but because of the choices your brain makes about what is important to expend energy on. Likely this isn't a set choice so if your brain decided stress or inflammation were more important one day it could crash you and make you bed ridden (as those with reoccurring back pain may have experienced). This could also be the root of anorexia, by starving themselves they can temporarily shut down bad feelings which encourages the behaviour.