I agree with johnep - you should write something on your own as you can't just freely reproduce what you find on the Internet.
But check those, maybe you will find it useful:
Obesity WHO | Obesity MedlinePlus: Obesity Overweight and Obesity: Home | DNPA | CDC
You may prepare a questionnaire too - composed to find out if - for example - patients' eating habits are good or bad and give them some tips after revealing the results. But to do that correctly you really should do some research.
You may also prepare some small gifts for patients willing to take part in your action. Althoug I don't like stuff like that I observe that people simply love that. So you may consider this, but it's up to you if you find it the right way to attract them.