FOLLOW IN THEIR FAMOUS FOOTSTEPS : 3 SENIOR STARS BRIM WITH TIPS ON STAYING FIT.

Byline: Carol Bidwell Daily News Staff Writer

The older you get, the more important it is - for both your body and your mind - to stay active, say three celebrities in their 70s who will lead a March 1 fitness walk for Southern California seniors.

Ed McMahon, 73, of Beverly Hills, Steve Allen, 75, and his wife, Jayne Meadows, 71, of Encino, will lead as many as 3,000 marchers age 50 and older in one- and three-mile walks in Culver City. The FHP Health Care Los Angeles Marathon Senior Walk is designed to encourage more seniors to stay fit.

McMahon, who entered the nation's consciousness as sidekick to late-night talk-show host Johnny Carson and who now travels the country as spokesman for Nabisco, American Family Publishers, Colonial Penn insurance and a cookware manufacturer, said he couldn't keep up the pace if he didn't make time to work out. He said he hopes his participation in the fitness walk will encourage others.

``I figure if people see me out there, they'll figure, `I can do that,' '' McMahon said.

Heart-pumping, fast walking is a low-impact aerobic exercise that's great for seniors because it can ease the pain of osteoarthritis by strengthening muscles and can slow the advance of osteoporosis, the bone-density loss often experienced by postmenopausal women, said Dr. Andrew Wong, chief of rheumatology at Olive View-UCLA Medical Center. And a walk can also help reduce stress, clear the mind and keep blood pumping to the brain, he said.

McMahon, a Marine who taught fighter pilots to fly combat planes during World War II and flew attack missions himself during the Korean War, said fitness has been part of his regular routine - except for a couple of years when he ate and drank too much and exercised too little. Now, he follows a low-fat diet and walks daily on a treadmill.

``My wife and I have dueling treadmills,'' he laughed. ``She's on the phone and I watch TV while we walk.''

And three days a week he works out with a trainer, lifting weights for an hour.

``The older you get, the more vital it is to maintain your vitality, your pep, vim and vigor,'' McMahon said. ``The worst thing in the world for an older person is to shut down. Some people who have retired, they've just drifted by the wayside. I have a lot of pizazz, and I never think about how old I am. I wake up in the morning and I'm ready to go. I'm a hard-charger. I have no intention of stopping until I'm stopped.''

Meadows and Allen say a continuing fitness regimen keeps them on the go. Allen, who created and hosted TV's ``Tonight Show'' in the 1950s, is an active playwright, actor, musician and songwriter. Meadows is an actress who has been nominated for five Emmys, winning one. She frequently appears on TV and on stage, most recently touring with her one-woman play, ``Powerful Women in History.''

Allen's workouts are usually in the pool, where he edits and rewrites songs ``in my head'' as he swims, usually for 30 minutes to an hour at a time.

``You can use your brain for either analytical work or creative work at times when most people don't do that,'' he said. ``I don't waste any time.''

Meadows climbs on her treadmill every day for a 20- to 60-minute workout. ``I tried walking outdoors, but being who we are, it became a privacy issue,'' she said. She also takes tap-dancing lessons three times a week.

``I couldn't live without exercise,'' Meadows said. ``My mother lived to be 93, and she walked five miles a day because she never learned to drive a car. I believe that was what kept that woman's brain clicking up to the moment she died.''

Allen and his wife of 45 years follow a low-fat diet and visit a Santa Monica spa occasionally to ``get religion'' where diet and exercise are concerned.

Meadows, who came from an athletic family (she taught her husband to swim), said she stayed active without formal exercise periods when she lived in New York, ``where it's nothing to walk five or six miles a day'' shopping and going to and from work.

But with age came the onset of arthritis in her hands, which forced her to give up guitar lessons; in her arms, which made it hard even to brush her hair; and in her feet, which made walking painful. The answer, she discovered, was dancing lessons. Tap dancing made her feet limber, and Spanish and Hawaiian dancing, which incorporate lyrical hand movements, made her arms and hands flexible again. She's no longer in pain and looks forward to dance classes at a Valley center.

``Nothing makes me happier - other than my grandchildren - than going to my dance class,'' Meadows said. ``It's just plain fun.''

Age and lack of fitness creeps up on many people, Allen said.

``If you're under 20, it's almost impossible to be lazy; you're riding a bike or playing baseball,'' he said. ``After you pass 50, it begins to occur to you that exercise is as important as eating right. It's just common sense. Generally, if you maintain good health, your physical and mental abilities will always be better.

``I do most of my work with my brain, and it's absolutely clear-cut that on days when I don't get enough sleep or haven't exercised for three or four days, I do not think as clearly or as fast as on days when I do get exercise,'' Allen said. ``Keeping moving is as good for your brain as it is for your body.''

Get ready to walk it

Not up for the Los Angeles Marathon on March 2?

Then the FHP Health Care Los Angeles Marathon Senior Walk, the day before the 26-miler, may be just your speed. The event, which includes one- and three-mile walks, begins at 9 a.m. and winds up at noon. It begins at Overland Avenue and Washington Boulevard in Culver City, and courses through the Sony Pictures Studios lot.

Deadline to sign up for the event is Friday. Entry is free and although the event is designed to encourage seniors to exercise their way to more productive and energetic lives, it's open to family members of all ages. Walkers can register at local senior centers or by calling [phone].

Participants will get free refreshments and a goodie bag and can meet and talk with celebrities who will include Steve Allen, Jayne Meadows, Ed McMahon, Margaret O'Brien and Virginia Mayo.

Free transportation will be provided to and from Sony Studios from various locations and senior centers throughout the Southland, including:

Holy Cross Hospital, 15031 Rinaldi St., Mission Hills.

Northridge Hospital Medical Center, 14500 Sherman Circle, Sherman Way Campus, Van Nuys.

Glendale Adventist Health, 381 Merrill Ave., Glendale.

Virginia Park, 2100 Virginia Ave., Santa Monica.

Ward Villas Senior Center, 1177 W. Adams Ave., Los Angeles.

Westside Jewish Community Center, 5870 W. Olympic Blvd., Los Angeles.

CAPTION(S):

2 Photos, Box

Photo: (1) Jayne Meadows and Steve Allen are pumping up enthusiasm for the March 1 FHP Health Care Los Angeles Marathon Senior Walk

(2) Ed McMahon keeps in shape by walking and weightlifting.

Box: Get ready to walk it (see text)