Five years ago, Frances Kuffel, a Brooklyn-based dog walker, became a real-life "biggest loser" after chronicling her 188-pound weight loss in her critically acclaimed memoir, Passing for Thin. The size-6 phenom (formerly size 32) became an instant It girl, landing a segment on Today and a profile in Time. But three years—and countless chicken-parm binges—later, Kuffel regained half of the weight. Now she's documenting her battle in her latest book, Angry Fat Girls. Kuffel's explanation for why she and other overweight women just can't seem to put the fork down may surprise her loyal fans: "We are biologically condemned," she explains. "It's not our fault."

Kuffel says she suffers from a raging addiction to high-fructose corn syrup, which she calls "high-grade heroin." She claims the stuff triggers the same dopamine surges in her brain as coke did for, say, Robert Downey Jr. At any given moment, she is racked by an urge for a fix, largely because her drug of choice, unlike coke, is ubiquitous, cheap, and legal. As for the success of all those formerly pudgy celebs like Valerie Bertinelli and Kelly Osbourne, Kuffel says, "They are either biologically lucky or work so hard at it that it's become their life."

Perhaps. But plenty of people manage to stay slim throughout their lives, thanks to good old-fashioned diet and exercise. And if anyone knows about such discipline, it's Kuffel. She lost half her body weight due to a spectacularly rigid no-sugar, no-flour, no-snacking diet. It was tedious, demanding work—measuring the food, hitting the gym, attending all those 12-step meetings.

It's called willpower. But Kuffel says it's not that simple, citing emotional reasons for her weight gain as well, namely a lifelong battle with depression. And, most surprisingly, she assigns some blame to the $40 billion weight-loss industry, which, she says, isn't truly interested in helping people lose weight, because if everyone got skinny, the industry would go belly-up. Food for thought.

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