What made Larry Brown's addiction acceptable was that it was, at least on the surface, good for him.

He was in his early 40s and running an impressive 50 miles a week. So what if it consumed him, if he thought about it even when his feet weren't methodically hitting the pavement or carrying him across a finish line; if he became angry when the weather, or something else he couldn't control, kept him from his workout?

"My PR (personal record) in a 10K was 33:16," says Brown, now 63. "I was good enough to where it caught me, and I was blinded by that."

Even when he developed prostate cancer, and was sitting in his doctor's office looking at an MRI of a bone tumor in his leg, he was still focused on running.

"That was my first question," says Brown, a Dallas insurance broker. "Not whether I could still work, or whether I'd be able to walk. It was, 'Can I keep running?' "

At a time when two-thirds of the U.S. population is overweight, and barely half of us exercise at least three times a week, Brown seems an anomaly. Yet experts say he is far from alone. Look around the gym, or on your favorite trail. Chances are at least several people were there yesterday and — no matter what else is going on in their lives — will be there tomorrow.

Officially, this is known as Overtraining Syndrome. Because of the volume of workouts, it occurs primarily among professional athletes, or those training for a long event such as a marathon or triathlon. Yet most anyone who works out can exercise too much; a workout's duration and intensity can matter as much as a compunction and compulsion to do it.

Yet there is an irony to this, says Sue Beckham, associate director of education at the Cooper Institute: Instead of leading to faster times and better health, too much exercise can be detrimental.

"Like anything, too much can be bad," Beckham says. "The way the body works is that we overload it, and by giving it recovery, it adapts. The problem comes when we don't have balance between overload and recovery."

HEED THE SIGNS

Overexercising often leads to such physical signs as loss of appetite, insomnia, fatigue and an inability to maintain what used to be a normal workout. Some people experience depression, mood changes and loss of self-esteem. Those symptoms could be related to exhaustion, or to chemical changes in the body, or by a decline in performance. No one really knows, Beckham says.

Even if someone doesn't have these signs, overexercising might be taking time from other areas of their lives, such as family.

Brown usually did his training runs while his wife and daughter were sleeping. He assumed that his long miles and time away didn't affect them. "I didn't know I wasn't all that easy to live with. I probably wasn't covering my bases very well," he says.

His family didn't talk to him about easing up, but his friends did.

"I'd say to them, 'You're not disciplined,"' says Brown. "I'd rationalize. It was willful blindness. I don't think at that particular time in my life they could convince me to do otherwise."

He knows now that his obsession was a matter of control.

"It was kind of a false sense of control, though, because you were one injury away from not being able to control it."

Or in his case, prostate cancer and a bone tumor — which was benign, but altered his running regimen. He eventually sought the help of a counselor, which he calls "the best thing I did."

MAKING EXCUSES

People who overexercise usually know they're working out too much, says Kirk Burgess, senior physical director at the Town North Family YMCA in Dallas; yet, they justify their actions. He knows because 10 years ago, that's exactly what he did. He ran the same 7.7-mile course every day without fail and couldn't seem to stop himself.

"Not only did I feel guilty if I didn't," he says, "but I was playing mind games. I thought I was falling behind the norm if I didn't run, that I wouldn't be ready for race day, that I felt inferior, that I wasn't on top of my game."

Eventually, the bone in his lower left foot "completely broke down." He had to have a bone graft. For six months, he couldn't run. Though he's back to it and is training for his 24th marathon, losing the bone is "what it took," he says.

"I was just like an alcoholic. It took hitting rock bottom to realize, you might want to slow it down a bit. You only have one body."

He keeps an eye out for overexercisers, like those who use the cardio and the weight machines every day. Or those who spend hours of each day on one piece of equipment. Though he rarely would tell someone what they probably already know, he might ask about their exercise program, and then talk about balance and about rest.

"The American College of Sports Medicine says rest days are as important as workout days," Burgess says.

Brown, who had his last cancer treatment 15 years ago, now has a rest day — Monday. He runs about 20 miles a week and takes two spin and two yoga classes a week. It's still time-consuming, but it just feels different, he says: "I feel like there's more joy and less intensity."

Sometimes he worries he'll revert to his old ways.

"I hope not, but I still wonder," says Brown, who records every workout in a notebook. "It's the old controlling nature. Will you revert back to your old self when things get a little stressful in business or in relationships? You wonder if it's your nature built into it."

He does have one more goal: To run 50,000 miles by the time he's 65. As of right now, he still has 1,000 to go — and until Aug. 3, 2011, to accomplish it.

HOW TO EASE UP

• Keep a training log. "Almost every time I was sick or injured, I'd go back to my log book and see where I had a big jump in my exercise overload, intensity or volume," says Beckham, a former triathlete.

• Make yourself take a day off. "You won't see results if you don't have a rest day," says Kirk Burgess of the Town North Family YMCA. You don't have to sit on the couch all day. Play with your kids. Go to an art festival.

• Consider hiring a coach. "Someone talking to you about what you're doing and how you're feeling is a safety net to step in and tell you it's too much," Beckham says.

• Be sure you're sleeping well and eating well. "A lot of times, I see people train really hard but aren't as serious about nutrition, so end up defeating the purpose of working out," she says.

If you can't seem to ease up, seek professional help.