1. The 40 year old "war on smoking" caused the number of smokers to drop from about one half to one quarter of American adults. While smoking is unhealthy and a high risk behavior, the fact is that a majority of ex-smokers tend to gain weight after quitting.
2. The denigration of marriage and the contempt poured upon housewives on the part of the mainstream culture encouraged women to leave marriages or seek outside employment to seek "fulfillment." "No fault" divorce laws, the so-called marriage penalty in the IRS code, and tax-subsidized day care also discouraged traditional homemaking. As a result, food preparation was increasingly outsourced to the restaurant business, where, at least at the fast food and lower price end, tended to appeal to the least common denominator. The increased use of prepackaged food (canned, frozen, etc.) is another example of this tendency.
3. The other end of weight control is exercise. To the extent that parents, guided by the permissive parenting that has been in vogue for decades, cater to their childrens' whims, buythem cars when they turn 16, give them spending money used for "junk food," and not require the completion of chores, they contribute to a failure of children to exercise. To a considerable extent, obesity stemming from a lack of enforcing discipline is a consequence of liberal permissiveness.
4. There has been in some circles a general denigration of masculinity in the traditional sense. Combined with the nihilism in the youth culture, a philosophy manufactured by and delivered to "independent, anti-establishment" youth by malefactors of great wealth (to steal some New Deal era rhetoric), many young men turn away from the sports fields and the outdoors to the inner space of mosh pits, student unions, and narcotics. The people in Georgetown, Cambridge, Beverly Hills, and the Upper East Side of New York fear the sort of young men in Army and Marine combat units than those with piercings, tattoos, and hair coloring not known to nature.
To a great extent, the increase in obesity among Americans is the outcome of governmental policies and elitist attitudes. Rather than more regulation and guilt trips, corrective measures should deal with root causes: permissiveness, hostility to traditional values, including opposition to the classical family unit, and denigration of manhood. These root causes stem from liberalism and its secular humanist and positivist underpinnings.