As for Tisch, his lean regime obviously has paid off. The hotel operator has lost 30 pounds over the past 20 years, and is now tipping the scales at 180. And you can see for yourself: He'll soon be appearing in a new TLC reality series where CEOs work in entry-level jobs in their own companies -- he did time as a housekeeper and bellhop.

How some CEOs do it

  • Barbara Smith, 54, president, B. Smith Enterprises

    Height-weight: 5 ft., 8 in., 145 pounds.

    Swears by: Juice "cleanses," three-to-five day fasts where she eats nothing but fruit and vegetable drinks (under a nutritionist's supervision).

    Weight change: Gained, and lost, eight pounds.

    Bad habit: Eating late at night after a busy day.

    Can't resist: Chicken wings, fried or otherwise.

    A former model, Smith has been as thin as 115 pounds. "That's not who I am," she said. When she hits 8 pounds over her ideal weight, she does a juice cleanse, either at home or a New York spa. On the way back from the spa, she treats herself to a new outfit at a nearby outlet mall.

  • Sanford Weill, 70, CEO, Citigroup Inc.

    Height-weight: 5 ft., 9 in., 205 pounds.

    Diet inspiration: When Wall Street and Citigroup were investigated by the New York State attorney general for stock-research conflicts, he resolved to get thinner.

    Weight change: Lost more than 40 pounds.

    Won't touch: Bread, dessert, gin.

    Soft spot: Wines like Chateau Margaux and Vega Sicilia.

    Weill started off by walking every morning with Charles Prince, his designated successor at Citigroup. Last January, he hired a personal trainer to come to his home at 6 a.m. After the investigation was settled, Weill allowed himself a gin martini.

  • Paul Charron, 61, CEO, Liz Claiborne

    Height-weight: 6 ft., 4 in., 207 pounds.

    Swears by: Treadmill, Special K.

    Travel strategy: On jaunts to Hong Kong, he packs sneakers and shorts to keep up running-and-weights routine.