The 70 guys from Unit K-3 at Lino Lakes claim to be the prison's most physically fit inmates. But even they might have gotten a jolt Wednesday from the exhibition booths on view inside the prison clinic.

There was the herpes poster: a cartoon of a shark eating a shark to illustrate the transmission of an incurable sexually transmitted disease. There was the photographic series of a rotting liver, showing how the organ shuts down when a patient goes untreated for hepatitis B. Across the way, men stood in line to get their blood sugar measured. The nurse found six inmates within an hour who had signs of diabetes, two of them weighing more than 260 pounds.

Over the hum of prisoners talking with nurses, a pop combo from the Department of Corrections provided theme music for the prison's third annual health fair, borrowing from Arlo Guthrie's "Alice's Restaurant'' to sing: "You can learn anything you want at our health fair restaurant ... "

The health event is part of a Corrections Department campaign to instill better habits in a group that may be the unhealthiest population in Minnesota. With daunting chemical dependency problems and years of hard living, Minnesota's prisoners and ex-cons present the state with a medical challenge of sobering proportions. At Lino Lakes, for example, it's estimated that about 20 percent of the offenders have diabetes and that at least 30 men are insulin-dependent.

The health fair started at Lino Lakes because many inmates there are about to obtain their freedom and go out into the world, but officials hope the event will eventually spread to the rest of the state's prisons.

"Ninety-five percent of our offenders leave us, and it is to society's advantage if they're smarter about health care," said Nan Larson, the department's health services director, as she scanned the crowd.

Soon she was dancing a bit of hip-hop with a group of offenders while a singer urged everyone to exercise "and keep those thighs moving."

Michael Hughes, 31, looked out over the crowd of familiar faces from Unit K-3. Hughes, who is 11 years into a 13-year sentence for second-degree unintentional murder, was working the sound board for the band.

"I know our unit is living more health-consciously than most," he said.

"Say they're serving up fries and meat on one food tray and on the alternative tray they're serving up soy-based food and fruits. A lot of guys are requesting that alternative tray, and that tells you a lot."

"We don't have TVs in our rooms,'' Hughes said. "We're out in the yard working out and jogging; the whole unit goes to the gym. So when we go to eat, there's a lot of motivation to maintain that fitness by choosing the right foods."

John Anderson, 52, of north Minneapolis, said he has extremely high blood pressure but has been reluctant for years to take medication.

"I don't eat pork or use salt," Anderson said. "The food is nasty. Most of the stuff I wouldn't feed to my dog. I must spend $120 a month on food I can get at the canteen."

For registered nurse Jane Welsh, the early hours of the daylong fair had already produced a large smile and a sense of accomplishment. Chances were good that by day's end she would detect more inmates who showed signs of diabetes.

What she'd found in the morning was concerning, Welsh said, but the fair also gave her a chance to get ahead of the challenge.

"People don't realize that diabetes is a very treatable disease,'' she said. "I have the opportunity to educate more of these guys."

Paul McEnroe • 612-673-1745