Question about raising happiness levels within oneself?

I was wondering what things there are that a person can do to raise their levels of happiness. Are there specific foods a person can eat to change their usual emotional states overtime. I heard that eating a lot of junk food can cause a person to be in a bad mood more often, and that eating a lot of healthy foods will cause a person to be happier more often. Now occupying oneself with positive things that they enjoy doing will obviously work, but I really just want to know if different food plays a part in this overtime or anything else. Please only positive and serious answers.