Dr. Walter Bortz may be 77, but that made him all the more qualified to deliver a wake-up call to a crowd of 170 youth Tuesday morning.

At this year's Mayor's Youth Conference, Mountain View's middle and high school students took a day off from their normal routine to learn about "the most important thing in your life -- health," Bortz said. "You can't do nothin' in life if you don't have your health."

Mayor Laura Macias agreed, and said she didn't mind hearing some health advice herself.

"If we are taking care of ourselves then we are going to be able to contribute more to what happens in our world," she said.

The event was organized by the youth advisory commission and the recreation department. The health theme was suggested by commission member Kacy Clark, who also designed the shirts for the event, said recreation supervisor John Marchant.

After Bortz's talk in the Center for Performing Arts, the teens broke into small groups to discuss caffeine, diabetes, eating disorders and similar issues. At the end of the conference the teens were asked what they had learned. Students mentioned "confidence," "stress" and "too much TV is bad for your brain." They also learned breathing techniques for controlling stress and how to "eat the colors of the rainbow" to ensure a proper diet.

Bortz is a well known author, Stanford medical professor and marathon runner. One of his assertions Tuesday was that genes and heredity "don't matter that much." Only 15 percent of a person's health problems can be explained by genes, he says. The rest is the responsibility of the individual.

He also told students tests have shown that TV reduces the amount of oxygen to the brain.

"I'm 77," he said. "I'm going to run a marathon in Los Angeles in a few weeks. There's not a darn thing wrong with me."

One of Bortz's books is called "We Live Too Short and Die Too Long." Many of his comments had a similar existential flavor.

"I don't want to end up in a nursing home," he said, before explaining how the most common reasons for ending up in one are preventable.

The answer to the most common health problem facing today's youth -- diabetes -- is as simple as eating appropriately and getting exercise, he said.

"One third of children born this year will develop diabetes," Bortz said, adding that it costs $11,000 a year to treat each diabetic. In the U.S., he said, "60 million people will soon have diabetes -- there isn't enough in the treasury to pay for that."

To illustrate how much exercise is recommended, a few students were given pedometers to measure how much they walked during the conference. It is recommended that a person walk 10,000 steps a day, but one student had walked only 1,200 steps by 1:30 p.m., even as she shuffled between events, which included a health fair in civic center plaza.

Students were given surveys at the end of the conference to suggest new city-run health programs.