This person has no idea how evolution works — they appear to be a Lamarckian of a particular dumbassed variety. In the case of obesity there is probably a mild selection pressure against it over the long term for modern humans.
Obesity leads to fewer pregnancies, worse pregnancy outcomes and the chance of a an earlier death to list merely are a few causes, as well as sexual selection occurring.
Over the long term — ceteris paribus — this will cause some selection pressure against it.
So most likely the exact opposite is occurring, even ignoring the Lamarckianism and stone-stupid stupidity.