Abstract: The invention relates to vectors and mammalian cells in a system useful for switching on or switching off gene expression in response to fatty acids, and a method of treating diet-induced obesity. In particular, a synthetic intracellular lipid-sensing receptor was constructed that constantly monitors blood fatty acid levels, processes diet-associated hyperlipidemia and coordinates reversible and adjustable expression of the anorectic peptide hormone pramlintide to reduce dietary intake, blood fat levels and body weight.