Answer
Behavior does not always follow attitudes. Although it is easy to understand the opposite, attitudes can stem from behavior. This is because people do not want to contradict themselves. Due to this, if someone does something then they may change their attitude. For example, if I say that oranges are the worst fruit and then start eating a lot of them then I would start to say they are the best.
Work Step by Step
The key to understanding this is cognitive dissonance, the idea that people want to reduce any internal contradictions. For example, you know fatty foods are bad for you but you continue to eat them.
