Plump girl + skinny guy =?

Depends on gene. Sometimes obesity runs is the family. Usually DNA and genes are based mostly on physical aspects . (Eye color, hair color etc. ) But the size of the child will be mainly based on how much the mother eats during pregnancy...The "lean gene" could be more dominant depending on the aspects that define the gene itself. For example, if the non-lean gene has blue eyes and the lean gene has brown. then yes, the lean gene would be dominant.