I was just wondering wether it would be possible to detect if the body is in a "fasting" state, via lasers attached to the body. If it is possible, what sort of laser would be needed?
If by a fasting state, you mean blood glucose levels, researchers seem to think it is feasible. See for example Pleitez et al. (1) and Guo et al. (2). Their designs both utilize infrared IR laser light to measure glucose levels in the skin.