Back in 2005, Jeff Friedman, who discovered the hormone leptin, appeared in conversation with NPR's Ira Flatow as part of a lecture series presented by Rockefeller University, where he heads their Laboratory of Molecular Genetics. The presentation was entitled "A War on Obesity, Not the Obese." A .pdf file of the transcript can be downloaded here. It's pretty long (26 pages), but I think Friedman does an excellent job explaining what we know about the science of obesity and the ethical implications of the "war on obesity."
"I think that to the extent that increased weight has health
consequences, people should do their best. It certainly is a good thing
to be fit. And it is a good thing to eat a heart healthy diet. And it’s
probably a good thing to make one’s best efforts to keep one’s weight
under control. So that means not doing much different than what
Hippocrates would have recommended. But I think at the same time we
have to recognize that those measures are rather limited in their
efficacy and that to make the leap therefore that people who are not
successful at keeping their weight off are at fault is just wrong
I don't agree with absolutely everything Friedman says in the interview, but we're definitely on the same page with the quote above.