Diego Maradona's refusal to return for regular checkups following a complex stomach operation in 2005 may have contributed to his losing battle against obesity, the Colombian doctor who performed the gastric bypass surgery said Thursday. Maradona was taken in an ambulance to a Buenos Aires clinic on Wednesday for problems associated with excessive eating and alcoholism. He's expected to remain hospitalized for at least a week. After undergoing surgery in the Caribbean port city of Cartagena in March 2005 to trim as much as 50 kilograms (110 pounds) from a ballooning waistline, Maradona never again contacted his Colombian doctors, Francisco Holguin, head of the Medihelp Service clinic, told Caracol Radio. "Any patient who undergoes this sort of procedure needs to submit to regular checkups to make sure they're following recovery instructions, but in Maradona's case there was no follow-up," Holguin said.