Earlier, a commenter pointed out how leaves in the spring could signal the body to release fat. The idea is that green leaves signal the arrival of spring and greater food availability, and therefore consumption of green leaves signals the body to release winter fat.
I found an interesting paper to support this. The tested how the addition of thylakoids derived from spinach leaves would affect hunger in healthy individuals. Adding the thylakoids decreased hunger and insulin. Also, a rat study showed that thylakoids suppressed hunger as well.