DALLAS (AP) — In the months after Doug Robinson started driving a truck, he noticed his clothes were increasingly more snug-fitting. He was already overweight but soon realized that spending up to 11 hours behind the wheel, frequently eating fast food and not exercising was a poor combination.

When his employer, U.S. Xpress, took part in a weight-loss challenge sponsored by the Truckload Carriers Association, the 321-pound, 6-foot-1-inch Robinson signed up.

So far, he's about 40 pounds into his goal of dropping 100. His truck's refrigerator is stocked with chicken, tuna and vegetables. And after his day's drive, he walks — either on trails near rest stops or just circling his truck.