A recent article in the Opinion section of the  New York TImes discussed the results from multiple studies about whether the mandatory posting of calories which is in effect in NYC has helped people to make better choices.

Knowing more doesn’t always change behavior in the absence of motivation / commitment.

See article:

http://www.nytimes.com/2009/11/13/opinion/13lowenstein.html“>http://www.nytimes.com/2009/11/13/opinion/13lowenstein.html