Grapefruit causes the liver to burn fat instead of storing it. It is rich in vitamin C as well as antioxidants. These work to boost detoxification enzymes. It also have a flavonoid compound called naringenin, which is what causes the burning of fat.
Avocados contain glutathione-producing compounds, which prevent the liver from a toxic overload. They are also a healthy source of fat, which may help with your fatty cravings after a night of partying. Instead of reaching for a unhealthy burger or something fried, try slicing up an avocado in some salad.