Jim Sensenbrenner went so far as to suggest President Barack Obama's wife was setting a bad example to children because her rear was too big.
The portly Republican, himself a well-known fan of unhealthy snack foods, suggested Mrs Obama was being hypocritical with her 'Let's move' campaign to tackle childhood obesity.
He was overheard making the comments in a mobile phone conversation while waiting at Washington DC's Reagan National Airport. Speaking very loudly, the 68-year-old said he had been attending a church auction three weeks ago when a woman came up to him and praised Mrs Obama.
He apparently went on that after listening to the woman he told her: 'She lectures us on eating right while she has a large posterior herself.'
After his comments were reported, a spokesman for Mr Sensenbrenner said the congressman would be contacting Mrs Obama to apologise.
Mrs Obama has not commented on the remarks.
