For two years now Bella Abzug has made losing a habit. First came her unsuccessful 1976 fight for the Democratic Senate nomination from New York, then her defeat in last year's New York City mayoral primary, and finally a startling upset in a special congressional election last February. By that time Bella was fed up—literally and figuratively. If there was anything more to be lost, she vowed, it would be her ever-increasing girth. "I gained 10 pounds for each of my six years in Congress," figures the omnivorous Abzug. "Now I'm trying to take it all off. I used to work 18 hours a day and grab a piece of cake or some candy. The kids in the office brought me junk food. Before, I was too busy taking care of the people. Now I have time to take care of myself."

Bereft of those hefty responsibilities, Bella has trimmed some 45 pounds from the physique that once made her Manhattan's roundest political figure since Fiorello LaGuardia. She has cut back to 500 calories a day, breakfasting on half a grapefruit, high-protein toast and coffee. Lunch consists of either fish or meat with a green vegetable. For dinner it's the same plus an apple. To firm up her gradually emerging silhouette, the renascent Abzug swims three times a week ("for 15 minutes without stopping") at a New York health club. She has also, at 58, become a blonde and shuns the hats that once were her trademark. "It's a new Bella," says her doting husband, Martin. "Hatless, officeless, but brilliant."

Though she has been consigned at least temporarily to political limbo, Abzug is co-chairman of the President's National Advisory Committee for Women and travels steadily to promote the ERA. It is on these peregrinations that her gustatory restraint is put to the test. "It takes a lot of resistance," she says, "because people are so hospitable. But I didn't even have a piece of corn last summer, and what I wouldn't give for a nice kosher hot dog!"

As always, however, Bella's keenest hunger is political. She disdains the three men who have recently bested her—Sen. Daniel Patrick Moynihan ("a disaster"), New York Mayor Edward Koch ("a bore") and Rep. William Green ("a nothing")—and hints broadly that she is plotting a comeback. "I would never run for any office lower than the ones I have held," she declares with characteristic modesty. "That leaves the House, Senate, Vice-Presidency or Presidency."