Because CYFIP1 deletion and reduced CYFIP1 expression are associated with more severe PWS (Type I) and hyperphagia in the PWP (FXS) and conversely, because gene duplication and thus, increased expression of CYFIP1 are associated with restrictive eating (Chang et al. 2019), in this study, we tested the hypothesis that Cyfip1 haploinsufficiency would increase premorbid compulsive-like behavior and increase consumption of palatable food (PF) in our BE paradigm (Babbs et al. 2018; Goldberg et al. 2017; Kirkpatrick et al. 2017). The gene discussed is CYFIP1; the disease is fragile X syndrome.