The invention features methods of enhancing whole body insulin sensitivity by modulating the endoplasmic reticulum (ER) stress response pathway in adipose cells. In one aspect, the methods involve targeting chaperone proteins important in the ER stress response pathway, for example, BiP and ERO-1. Another aspect features targeting the upstream transcription factors (e.g., CHOP-1 and XBP-1) of the genes encoding the chaperone proteins (and/or other ER proteins). Screening assays for identification of modulators of these ER proteins and/or transcription factors are also featured.