You have the best job in the world," people often tell me at parties, usually after I've mentioned a recent three-week eating odyssey, to scout restaurants for an article or track down recipes for a new cookbook. "Thanks," I respond, recalling the day when, for research purposes, I endured three consecutive lunches with chefs hovering over me to make sure I savored every last bite. "How do you food writers manage to look good?" people always want to know next. Ah, the million-dollar question.

Staying slim isn't easy when it's your job to eat. But image matters more than ever if you want to succeed as a cookbook author or a lifestyle guru. There's little hope of hitting the bestseller list without an appearance on a national morning show or, if you're a cook, your very own program on the Food Network. Though Julia Child was the first to demonstrate that nothing sells cookbooks like television, these days, domestic goddesses must be eye-candy like Giada, Nigella and Rachael, who can seduce viewers by looking as delicious as the food they create.

The culture surrounding food thrives on contradictory messages. On one hand, "gastro-porn" is rampant in books, food magazines and cooking shows that peddle scandalously gooey macaroni and cheese and "sinful" pastries. On the other hand, the diet industry thrives by urging us to cast off the pounds we put on making Rachael's favorite muffins. One pities the poor consumer, but what about us cookbook writers, who have to resolve this conflict to make our living?

To produce a good book, cookbook authors overeat, and to promote it, we starve—first trying hundreds of recipes, then going on crash diets. It's not a simple or especially healthy way to live. Yet for cookbook authors, survival of the fittest is no longer a metaphor. So we soldier on through our cycles of bingeing and abstaining, to give our books the best possible chance.

As I prepare for the 27-city marathon to promote my book, The New Spanish Table, I've forsaken the tapas, garlicky roast lamb and rum-soaked chocolate cakes of my research days for primly steamed fish and broccoli rabe. When I'm not busy perusing new diet or exercise books, I'm devising ways to maximize my five minutes in front of the camera.

Previous media gigs have taught me that V-necks flatter; to avoid bold prints and stripes; and that a trim, casual outfit is the wisest choice. I've learned that authors really do need to keep their chins up, shoulders back, their message clear, and to keep focused and smiling. (I've also learned that Hoola bronzing powder from Benefit takes the pounds and puff out of a hustling writer's face.)

But dieting—plus media training, plus makeup classes, plus a good demo tape—only takes you so far. In the end, nothing sells books better than an author who's passionate about her subject and comfortable with herself, both on the page and in front of the camera. It's the skill of authenticity, which Julia Child, bless her, had in spades.

Like everything related to publishing, it requires labor. That's why I find myself waking up at night—with stomach rumbling—to scribble down talking points, or standing in full costume and makeup before a mirror, praising my book to an imaginary TV host. And when another celebrity chef tries to entice me to undertake a 30-course degustation menu, I'll say no, thank you, for now. As long as I need to promote my book, I'll starve. That is, until I start the next one, and binge again.

Anya Von Bremzen is the author of The Spanish Table (Workman, Dec.) and a contributing editor at Travel+Leisure magazine.