To the Editor Liu and colleagues1 have downplayed the role of hereditary factors in their study of obesity in early-onset colorectal cancers (CRCs). Family history is not reliable in excluding hereditary CRCs; an editorial in JAMA on a study identifying Lynch Syndrome (LS) noted that the “study results should remind clinicians that simply asking about a family history of CRC in a first-degree relative will miss the majority of patients with LS: only 43% of patients with LS had such a family history.”2