Trancework is one of the things we do in our coven. The most popular uses at home have been sleep and studying, aside from the altered states we work with in group. Basically, all it does is give you access to your brain's operating system. You CAN make changes, including very dramatic effects, although big permanent changes typically take lots of repetition. I've seen people learn things in 10 minutes while tranced that normally take weeks or months in ordinary consciousness, because you can show things in there rather than just describing them.
What this means is, you need to think about what and how you want to change. The typical framing used in the waking world isn't all that helpful. But you can do things with trancework that you can't do any other way. Consider setting an intent that you want to move your body more. Try raising your awareness of what things actually taste like -- the nutrients in fruits and vegetables, the additives in processed food, etc. Or tune into the signals of hunger and satisfaction, if you've lost touch with those. Body awareness is very easy to do with this technique. Are you trying to switch from less healthy to more healthy comfort foods? Trancework is great for making new imprints. You probably could tinker with your metabolism, but I'd be very careful about that. It's a lot easier and safer to alter your perceptions, your eating habits, or your desire to move around more. You're also more likely to wind up with healthier eating and moving habits, whereas focusing just on weight loss isn't necessarily healthy.
Sadly, most people writing about hypnosis don't actually know much about it. This is a fantastic tool, but to get the most out of it, you really want to read about the psychology of how the subconscious works and some mechanics of the brain, and then dig into some hardcore stuff about the levels of trance. You may cross into magical references for the deeper stuff because the clinical references don't go as far, although you don't actually need the deepest levels for basic reprogramming. It's just good to know what you're doing in there.
In other words: garbage in, garbage out.