'Health halo' effect: how healthy foods can make us fatter
28 June 2012 Last updated at 10:03 BST
The labelling of some foods as low-fat may be encouraging us to eat more and so contributing to the continuing rise in obesity according to Pierre Chandon, a Professor of Marketing at Harvard Business School.
His research suggests we eat more if we believe foods are good for us in what he describes as a "health halo" effect.
The final episode of The Men Who Made Us Fat is broadcast on BBC Two at 21:00 BST on Thursday 28 June. Catch up on all three episodes online via iPlayer (UK only) at the above link.
You can join in the debate and leave your comment on Jacques Peretti's blog via the link.