Update: I should say where I stand.
I may be in a minority, but I don't believe obesity stems primarily from an individual's choices.
I may not be in the minority in the UK, however, where personal choice's role in obesity is considered just one factor among others, including class, location, and time (time in history, as in "the Britian of today"):
"Although personal responsibility plays a crucial part in weight gain, human biology is being overwhelmed by the effects of today’s ‘obesogenic’ environment, with its abundance of energy dense food, motorised transport and sedentary lifestyles. As a result, the people of the UK are inexorably becoming heavier simply by living in the Britain of today. This process has been coined ‘passive obesity’. Some members of the population, including the most disadvantaged, are especially vulnerable to the conditions."Not to say individual responsibility doesn't count, but there are strong social and political forces acting against personal choice.
"The evidence is very clear that policies aimed solely at individuals will be inadequate and that simply increasing the number or type of small scale interventions will not be sufficient to reverse this trend."
- Tackling Obesities: Future Choices - Summary of Key Messages, Government Office for Science