WASHINGTON (AP) _ A decade ago, Martina Navratilova decided that she was going to sacrifice everything, including food, in order to become the best female tennis player in the world. Once she realized her goal, Navratilova found out that it takes even more work to stay No. 1.

Life at the top can make even the best players crumble under the intense pressure. Just ask Bjorn Borg or John McEnroe.

That's why Navratilova, coming off a year in which she lost more matches than in the previous three years combined, called 1985 the ''most satifying'' year of her career. It's not that she lost a step; it's just that the competition picked up the pace.

''I had to work harder last year than I ever did before,'' Navratilova, 29, said. ''Last year was more gratifying than any other year because everyone got better. To stay on top after facing that type of challenge made 1985 the most satisfying year of all.''

Navratilova, a former butterball who has lost 20 pounds since breaking onto the pro circuit, humbly takes partial credit for the sudden challenge that the competition has provided her.

''It used to be Chris (Evert Lloyd) and me, and then everyone else,'' she said. ''But then the other players saw what can happen when you put in the work. They saw the results, and they took the bull by the horns and did it.''

The women's tennis book of records has Navratilova's name all over it. The all-time money winner in tennis history, her 74 consecutive singles victories is a record seemingly beyond reach. In addition, she teamed with Pam Shriver to win 109 straight doubles matches.

The statistics seem to indicate that Navratilova slipped a bit in 1985. After all, she lost the French Open and the U.S. Open. And, she lost her No. 1 ranking for the first time in three years before reclaiming it with a triumph in December at the Australian Open.

Despite this, Navratilova says she played the best tennis of her life in 1985.

''If I had just maintained my level of play from the past few years, I'd have never had stayed at the top,'' she said. ''I had to work harder than ever before, and it paid off.

''In 1983 and 1984, I got away with playing average tennis,'' she says. ''Let me tell you that even though I lost the 1985 U.S. Open (against Czechoslovakia's Hana Mandlikova), I played better than I did when I won the thing in 1983.''

While Navratilova's dedication and effort to maintain her top ranking has made an impression on the rest of the players on the tour, it has shocked Mike Estep, her coach since the summer of 1983.

''The thing that amazes me about Martina is her continued drive to be No. 1,'' Estep says. ''She still wants to get better, and while she may lose a step as she gets older, she's smarter on the court and even better than she was a few years ago.''

Navartilova smiles when she tells the story about the time recently when she and Lloyd spent an afternoon watching a replay of their Wimbledon matches of 1978 and 1979.

''It was like we were playing in slow motion,'' she said. ''We laughed about it and agreed that if we still played that way, we'd be looking for another job.''

Navratilova once said she would seriously consider retirement when she became 30 years old. Although that day is eight months away, she now claims she's going to stick around for at least a few more years.

''The older you get, the more you appreciate what you have,'' she says. ''I just completed the best year of my life, on the court and off.''

Off the court, Navratilova enjoys skiing and basketball, two sports that have high injury rates. But she laughs when asked to explain why she takes such risks.

''If I was afraid of being hurt, I wouldn't drive a car or fly in a plane,'' she says. ''For that matter, if you stay at home and do nothing, you could still get killed if a plane rams into your house. In other words, it's foolish to worry about something you don't have any control over.''

The thing Navratilova has the most control of, her No. 1 ranking, is exactly what she covets most of all.

''I can't see myself as anything but No. 1'' she says. ''I'm at the top and that's where I intend to stay.''

End Adv PMs Thur Jan 9