WARWICK — The city has joined the fight against obesity and Mayor Scott Avedisian is leading the charge. Make that the challenge.

The first-ever “Mayor’s Fitness Challenge” invites fourth through sixth graders to participate in a semester-long fitness program.

The event, which kicks off today and runs through May, encourages youngsters to lead physically active lives, not just at recess or in gym class.

Participation is voluntary. Children who do take the challenge will be asked to log their minutes of physical activity in a journal. Sports and fitness activities count, but so do chores such as shoveling snow, vacuuming and raking leaves.

The school with the greatest number of total activity hours come springtime will win a lunchtime party this June, the mayor said.

The percentage of children who are considered obese or overweight is on the rise nationwide, due, in part, to diet and inactivity. Those children are at higher risk of developing serious health problems such as Type 2 diabetes and asthma and emotional problems such as low self-esteem and depression.

This reality has not been lost on the mayor, who says it’s time for Warwick students to get in shape.

“We’re hoping that this will provide a fun and spirited way for our children to become more active,” Avedisian said. “Even an extra 30 minutes a week, over time, will make a difference.”

And will the mayor don his sweats?

“Avedisian said that schoolchildren can rest assured that he’s not going to be sitting idly by while they’re out and about — in addition to regular sessions at the gym, he’s joining other city employees on a team to participate in the statewide “Shape Up RI 2007” event, a statement from his office promised.

For now the student fitness challenge program is limited to fourth, fifth and sixth graders. If it is successful, the mayor said it will be expanded to include all elementary school grades and extended to a year-long challenge, starting in September.

School Department Athletic Director Emo DiNitto applauded the mayor’s effort. “I think it’s terrific. Anything that’s going to help us overcome this business of obesity is encouraging,” he said.

DiNitto noted that several Warwick elementary schools host similar personal fitness programs, all of which have seen success. “They’re all great because they serve a purpose,” he said.

cneedham@projo.com