The present invention relates generally to enzyme assays and more particularly to a rapid, sensitive, reliable and robust homogeneous assay for acetyl CoA carboxylase activity comprising a coupled enzyme assay in a scintillation proximity format suitable for high-throughput screening. In one aspect, the assay couples ACC and FAS and the product, palmitic acid is then detected by scintillation counting. The invention also relates to the identification of modulators of ACC activity.