The brain is the central regulator of appetite and body fatness, and genetic variation that affects body fatness tends to act in the brain.  One important site of variation is the POMC gene, which codes for a signaling molecule that suppresses food intake.  A new study shows that Labrador retrievers often carry an inactive version of the POMC gene, causing them to be highly food motivated, obesity-prone-- and perhaps more easily trainable. 

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