I have a friend who has been using somebody else's body for the last 20 years or so. His real body has apparently been on loan or in some form of temporary retirement, it's not clear which. His real body is the one he had when he was around 16 years old and gradually, almost without his realizing it, that body vanished and another one took up residence beneath his neck (actually, I suspect, starting right below the first chin).

The body he is currently using has a much larger waistline than his real body, and to hear him tell it, the front panel of his current body also extends further outward than the front panel of his real body. He is gradually coming to terms with the fact that his current body has been with him longer than his real body, which apparently was only there a few glorious years, but he nevertheless is greeting middle age with the conviction that he is living in a rental unit that will go away with diet and exercise.

I know exactly how he feels. I, too, am once again in search of my real body, which took a temporary leave about some 17 years ago and hasn't been seen since. Last week, in what is becoming an annual rite of passage into the bathing suit season, I resolved to get it back.

"I've started doing exercises again," I announced to my son the 16-year-old one morning.

"Uh, Mom," he said, skeptically, "you'd better show me what you're doing because I strongly suspect you're probably doing it wrong."

It should be noted here that mine is the generation that thought hiking to the mailbox was the junior Olympics. Mine is also the generation that had the poor judgment to produce teen-agers who think nothing of lifting weights for an hour or doing 120 situps followed by 60 pushups followed by five miles of jogging.

That evening I appeared in his room, got down on the floor and to my great delight executed a situp that would have done a high school athlete, at least in my day, proud.

He shook his head. "Mom," he said, with his usual diplomacy, "that's ridiculous."

"It is not!"

With that he got down on the floor and elevated the lower part of his legs across the weight bench. Then he launched into a bizarre ritual that involved raising his chest to his knees and lowering his shoulders back down to the ground again. "This is the way to do it," he said.

"I can't do that," I said.

I was right. Three inches off the floor, my shoulders stopped moving. Clearly, between the two of us, there was a distinct difference. It turns out that it is the abdomen. His abdomen is as flat and hard as a wall, which makes it different from mine on two counts.

Next we proceeded to leg lifts, which long experience has taught me are best executed by making sure no one is watching you and then folding your knees quickly and thrusting your legs out at a 45 degree angle and pretending you got there without cheating.

"Wrong," he said, lying down next to me, his legs comfortably extended three inches off the carpet. "Your legs are way too high." He watched as I lowered them five inches. "Still too high." Four inches further down, he made up for a lifetime of curfews and forgotten allowances. "That's it," he announced. "Now hold it there for half a minute."

I am now exercising with my 2-year-old. She sits on my ankles every morning while I do situps, providing an anchor for me and a counting opportunity for her. Yesterday morning I ran out of steam at five, gasped it out under my breath, then got my strength back in time to say "six" aloud. When you're headed for 15, momentum is everything.

"YOU FORGOT FIVE," she bellowed from her perch.

"Seven," gasp. "Eight."

"FIVE" she yelled. "YOU FORGOT FIVE."

"Nine," pant, "10," pant.

"FIVE! YOU DID FIVE YESTERDAY MORNING BUT YOU DIDN'T DO FIVE TODAY!"

"Eleven," pant, "FIVE," gasp.

A mere week has passed since the search for the real body began and as we all know it is far, far too soon for visible results. I have every confidence that the 19-inch (or was it 21?) waist that goes with my real body is only six or eight pounds away, roughly the same place it was at the beginning of last summer.

Each situp has the name of a child on it and each is done with the slightly malicious conviction that all those 16-year-olds who are setting artificially thin standards and driving the rest of us to diet and exercise had best enjoy their moment in the sun. In a mere 20 years or so, when the members of my generation will have finally found our real bodies, we can sit back and cackle as our children start the long, painful search for theirs.