If you’re chronically stressed, your fat-free-mass literally start to break down. Stress researchers call this wear and tear allostatic load. The fat-free-mass breakdown is caused in part by collagen proteins being used faster than they can be replaced. More preliminary research suggests that chronic stress may also contribute to obesity through direct mechanisms (causing people to eat more unhealthy foods) or indirectly (decreasing sleep, decreased exercise tolerance, blood sugar management issues).