HOLLYWOOD, Oct. 17— Iced tea is in. Hollywood, which has made an art of eating out, is changing that art to fit the contemporary passion for physical fitness.

Gone are the two-martini, butter-and-sauce lunches at the accustomed French restaurants. And because of the trend, not only are the wheeler-dealers healthier, but also ''more muscle is going into the decision making in the afternoons,'' according to one studio executive.

''Even white wine has fallen into disuse; the lingua franca of the lunch set is iced tea with Sweet'n Low,'' says John DeSimio, a publicity executive at 20th Century-Fox, who describes himself as ''the lowest level of management allowed to eat lunch out.''

''The people who aren't drinking iced tea are drinking Diet Coke with lemon,'' says the Fox production vice president, Larry Mark.

''Six years ago, during my first breakfast in Hollywood, I was offered everything from omelets and sausages to french toast,'' says Ed Roginski, marketing vice president at Universal. ''I took it as a gesture of concern. The last four breakfasts I've had, I had my choice of fresh fruit or juice and bran muffins or dry toast. That was also presented to me as a gesture of concern.''

In Hollywood, meals are used to court directors or producers or actors or agents or studio executives - depending on one's own needs and prominence. ''I can't afford to snub some hotshot who just graduated from Southern Cal because tomorrow he may be Steven Spielberg,'' says one low-level studio executive.

But more and more executives are using their lunch hours to meet with their personal trainer or take their aerobics class. ''I can't get people to have lunch anymore,'' says Mr. Roginski. ''They all want to have breakfast.''

Or vice versa. Sherry Lansing, an independent producer who used to be head of production at Fox, still has five lunches and three dinners out a week. However, she has traded in her five-day-a-week breakfast meetings for a 7:30 A.M. game of tennis. ''Our group has reached an age where people we know are getting sick,'' says Miss Lansing of the pack of prominent executives and producers sprinting past 40. And she thinks a ''big reason'' for the success of Mortons and the Ivy, two trendy restaurants, is their relatively austere menus that include mesquite-grilled fish and chicken.

In any case, how to keep from having lunch remains the same. '' 'We must have lunch sometime,' means we never will,'' says Gareth Wigan, an independent producer. Says Tom Wilhite, another independent producer, ''It only means something if you say, 'What day do you have free for lunch? Let's set it up.' ''

''Even then,'' says Mr. Mark of Fox, ''if someone wants to get out of it, he just keeps changing the date.'' Act III, Scene 1 For Norman Lear ''The sale to Coca-Cola represents the second-act curtain in my life,'' says Norman Lear.

Act I was creating ''All in the Family'' and a half-dozen other realistic situation comedies that made Mr. Lear extremely rich and famous at the same time they were changing the nature of half-hour television. Act II was being co-mogul with Jerry Perenchio astride the empire of Embassy Communications that Mr. Lear's television success allowed him to build.

What Mr. Lear has chosen to keep from the sale of Embassy to Coca-Cola for $485 million is forming the basis of a new company, Act III Communications. For the moment, Act III is mostly the movies of Rob Reiner. Mr. Reiner, to whom Mr. Lear gave his first acting break as Archie Bunker's son-in-law on ''All in the Family,'' has just finished directing ''The Body,'' from a Stephen King book that is more comic than Mr. King's usual tales of horror. Mr. Reiner will next direct William Goldman's picaresque fairy tale for adults, ''The Princess Bride.'' Mr. Goldman has written the script. Both movies are owned personally by Mr. Lear.

Together, Mr. Lear and his Embassy partner, Mr. Perenchio, own Richard Attenborough's film version of the Broadway musical ''A Chorus Line.'' But closest to Mr. Lear's heart is ''A Wrinkle in Time,'' Madeleine L'Engle's classic children's book about three children who save the universe. He bought ''A Wrinkle in Time'' five years ago and intended to make it as his first Embassy movie.

''I've had six scripts,'' says Mr. Lear. ''The first writer was Robert Bolt. One problem is that it's such an expensive picture to make. But I think that finally the script is right and I'm in negotiations with a studio.''

As to why he sold his empire, the answer is an enigmatic, ''It was time.'' Shooting a Sequel To an Unhappy Love Story Time passes. Twenty years ago, Claude Lelouch directed Anouk Aimee and Jean-Louis Trintignant in ''A Man and a Woman.'' The Academy Award-winning foreign-language film of 1966, it was one of the few foreign-language movies ever to score a major success at the American box office. Last week, Mr. Lelouch began shooting a sequel to his unhappy love story. ''A Man and a Woman: 20 Years Later'' stars Mr. Trintignant, who is now 55 years old, and Miss Aimee, 53.

According to Mr. Lelouch, 50 today is ''le bel age,'' the beautiful age for a love story. ''The seat of power rests with people that age,'' he says, ''and kids of 25 are more old-fashioned than their parents.''

''A Man and a Woman: 20 Years Later'' begins 20 years after Miss Aimee left the race car driver Trintignant at the end of the first movie because she was still half in love with her dead husband. Her parting line was, ''If I ever forget him, I'll call you.'' At the beginning of the sequel, she does. Newman Picking Up A Pool Cue Again Continuing its plunge into films for adults, Walt Disney Productions will make a sequel to the 1961 Paul Newman movie ''The Hustler.'' Mr. Newman will star in the sequel, which will be directed by a very un-Disneyesque director, Martin Scorsese.

Once the young pool hustler who met his match in Minnesota Fats, played by Jackie Gleason, Mr. Newman will now be the mentor to a new young pool shark, Tom Cruise. Although Disney has not formally announced the project, the movie -tentatively titled ''The Color of Money'' - is scheduled to go into production in January under Disney's adult label, Touchstone.

Disney had to get a license from 20th Century-Fox to make ''The Color of Money,'' since ''The Hustler'' was a Fox film. Just 14 months ago, Michael Eisner, Disney's new chairman, and Barry Diller, the new chairman at Fox, worked together as the top team at Paramount.

Before Mr. Scorsese and Mr. Cruise were involved, ''The Color of Money'' bounced around two other studios. It was turned down by Fox before Mr. Diller arrived, and it was dumped by Columbia when that studio was having a fire sale of its projects. According to Mr. Eisner, his toughest task was convincing Paul Newman that Disney's movie division now stands for something more than Mickey Mouse.

A 'Star Wars' Duck

George Lucas's new movie, ''Howard the Duck,'' will star Lea Thompson, who most recently played Michael J. Fox's mother in ''Back to the Future,'' and Jeffrey Jones, the knuckle-headed Emperor Joseph II in ''Amadeus.'' Based on a Marvel Comics character - a duck from another planet who will be played by a man dressed as a duck - ''Howard the Duck'' will start filming for Universal on Oct. 28 with Willard Huyck as director and Mr. Lucas as executive producer. Lucasfilm, which is tight-lipped when it comes to plots, would only describe the movie as ''the Duck version of Indiana Jones.''