Thesis

Start by identifying a few general topics that interest you. Then browse the literature to assess the state of knowledge on those topics. (What do we know about that topic and what do need to know? Which topics seem "ripe" for some more research?) That should help you narrow it down a bit.

Then choose 1 or 2 topics and do a more detailed literature search on. Use the skills you should be learning in school to evaluate the literature and begin to brainstorm a couple of possible ideas for your project. Meet with your advisor to discuss the feasibility of actually carrying out a few of the ideas you have brainstormed.

That process should help you find a topic that is both of interest to you and also feasible given the resources at your disposal.

What topic did you originally choose? Maybe you can tweak it a bit and not have to reinvent the wheel!

Is this a thesis based on lit search or experimenting you do yourself? I would think if you were doing the lit search thing, to research the impact of food rewards in people in general might be interesting. You could include Pavlovian theory. You could tie it into cardio health too.