TNF should not be confused with TGF. Though similar in reaction, their action is through a different mechanism. Endogenous TNF production is normally a response to infections.
Once released TNF kills fat cells through necrosis. Let me explain that. Every cell in genetic material contains specific DNA for cellular death. The exception is cancer cells. When the body has either the need for energy or factors contained within a cell the DNA is triggered through one or more chemical messengers to give up the factor. In the case of TNF, the message is “commit cellular suicide”. When applied to fat cells (adipocyte) the result is a reduction in adipose tissue. It sounds cool, but the same signal can kill muscle cells as well.
L. Rea (2002) - Chemical Muscle Enhancement Bodybuilders Desk Reference