Hi there...
That is quiet a broad topic and there are many ways you can approach it. You can do a simple questionnaire based study where you could formulate a questionnire which will give you the information you need and present it graphically or statistically. Or a complicated correlative study where you compare the ideologies of new physiotherapy students of 1 st year to those of final year students regarding Obesity. That way you will be able to find out whether students had any idea about obesity and how the view changes after being educated about it.

Its a very interesting topic. And will provide some really useful information...

Good luck.