On a 5 hr bike ride your body is going to go into a similar state as intermittent fasting with all your glycogen being burned off. Similar to fasting this frees up energy and allows the garbage in your system to be burned off.
Your Web App sounds interesting. Though I wonder if it is just helping to manage the symptons rather than addressing the source of the depression. Procrastination may be a sympton and not the cause of depression.
Unfortunately, for many people mental illness and depression is a result of very real chemical imbalances in the brain. Also, for other people letting go of a toxic relationship or unhappy marriage miraculously cures depression.