Emma, I strongly disagree that fat is a "feminist" issue.
Certainly the fashion industry is guilty of showing unattainable (and often unhealthy) "standards" of female beauty. But who edits and publishes these magazines? Who writes articles for them? Who buys them? Almost invariably, it's women, right down the line. "Women beware women" was never more apt.
And this gives the lie to it being a "feminist" issue. If it was a feminist issue, the problem would by definition be that men were discriminating against women who weren't stick-thin, or that men were advocating this body image. The fact that men aren't doing this and it's *women* doing the advocating means that it's impossible for it to be a feminist issue, for the same reason that it's impossible to be racist to someone of the same racial group as you. Sure, it's specific to women, but it doesn't make it feminist.
Re that Times article, it commits a basic error in logic - it assumes that "overeating" and "underexercising" are fixed values. That's obviously complete rubbish. Lumberjacks, soldiers, professional athletes and other groups who do hard physical exercise every day *require* something like 5000 calories per day to do this work. "Overeating" for them would be 6000 calories; "undereating" would be 4000 calories. Compare and contrast to a couch potato who never leaves their air-conditioned/heated house, for whom 1000 calories per day may be overeating.
When you add in the various other factors, all they do is modify where your baseline for "overeating" and "underexercising" kicks in. In other words, if you're in a heated house and you're eating the same calories as someone in an unheated house, you might need to run 2 miles extra per week than them, perhaps. If you don't then you're overeating (or underexercising), even though you're eating the same as them.
To misunderstand that is like saying "You drove due east from your house in central Ohio perfectly safely. I drove due east from central Manhattan, bounced off a zillion buildings and then fell in the river. What am I doing wrong...?" Sadly, there's a lot of apologists for fatness who make exactly this mistake. The fact that the Times would phrase their article this way is disappointing.