Crush some laxatives in YOUR food and leave a note not to eat it. It's not your fault if someone spends the day on the loo as you did warn them.....

Don't use any sort of laxative in your food- it can get you charged with poisoning someone. You can however put something that is spicy, but not spicy enough to cause medical issues on your "food" and bring a spare lunch to actually eat. Alternatively, set up a camera in the fridge area and get him on film, and use a dummy email account to forward it to everyone at work. Make sure to include yourself.

Start leaving the office at lunch and make sure people see you leave

Put a mousetrap in your lunchbox!

There’s really only one course of action left for you: start eating everyone else’s lunch. You’re doing the time, you might as well do the crime.

Time to break out the cell phone camera

Do you have an HR Department? Bring it up with them if so.

This is the stuff that creates violence in the workplace. Report your manager immediately.

Simple solution, get one of those lockable lunch boxes.