ANN ARBOR, Mich – Preston Brooks replaced lunchtime bacon double-cheeseburgers with submarine sandwiches loaded with vegetables.

And never looked back.

The 12-year-old sixth-grader credits his healthier outlook to an ambitious effort to tackle obesity in five middle schools.

“I’ve learned how to make better choices about what I eat,” Brooks said.

So have more than 1,000 other students. Since the Healthy Schools program began as a pilot program at one middle school three years ago, sixth-graders who have taken part in it have lost weight, lowering their blood pressure and cholesterol levels.

The project uses 20-minute lessons, motivational speakers and eye-catching props to teach kids about basic nutrition and encourage exercise. The program is a collaboration between Ann Arbor public schools and the University of Michigan Health System.

The 12-week program, which includes medical screenings OK’ed by parents, now is offered at all five Ann Arbor middle schools. About 1,200 sixth-graders are signed up, and about half of those are part of an ongoing study that’s tracking results and lifestyle changes.

Early results are promising.

Forty percent of those studied last year were considered “at-risk” in at least one medical screening category. Thirty-two percent were overweight, 9 percent had high blood pressure and nearly 10 percent had cholesterol levels above 200, a troubling sign at such an early age.

By last spring, students who were being tracked in the program had improved immensely.

Of the 292 students who took part in the study of 2005-06, 47 of 142 with high triglycerides reduced their levels. Nine of the 21 students who had cholesterol levels above 200 reduced them below that mark.

So, how did Ann Arbor do it?

Organizers followed this simple lesson plan: Teach good eating habits, promote fitness and nudge school administrators into offering healthier foods.

In the Clague Middle School cafeteria, for instance, french fries were replaced with baked potatoes. Bacon-double-cheeseburgers, high-fat meat pizzas and foot-long hot dogs were downsized or eliminated. Vegetables with dip and a fruit salad bar were added. School vending machines now offer water and fruit juice instead of soda.

Making these changes also meant challenging food service contractors whose bottom line relied on high-profit – and high-fat – lunch items.

“We really pushed the district and the food vendors more,” said Michael Hecker, the principal of Clague. “It may cost more, but it’s better for kids.”