Body fat accumulation is a major concern in the poultry industry. Therefore, knowledge about the molecular mechanisms that control de novo fatty acid synthesis and applied nutritional research that limits fat production in chickens is of critical value to the poultry industry. The ability for increased dietary protein concentrations to decrease de novo fatty acid synthesis in birds is correlated with a decrease in malic enzyme activity that is preceded by a decrease in malic enzyme mRNA expression (Adams and Davis, 2001). More importantly, the changes in malic enzyme mRNA expression occur with in 3 h of a change in the dietary protein level (Adams and Davis, 2001). The current research established that the changes in malic enzyme mRNA expression are proceeded by changes in the mRNA expression of the transcription factor spot 14. The current research also indicates that dietary proteins influence on spot 14 mRNA expression may be mediated by glucagon and/or thyroid hormone. In conclusion, it is well established that increasing dietary protein concentrations will reduce de novo fatty acid synthesis in birds and subsequently body fat content. As researchers continue to delineate the biochemical mechanisms by which protein causes this effect, practical dietary manipulations may be identified to control the body fat content of broilers and the identification of critical biochemical mediators in the process may lead to their use as genetic markers in the selection of broilers for leanness.