“Dateline NBC” featured Al Roker’s weight loss battle last night — warts and all. Roker’s trainer discussed how the NBC weatherman keeps off the weight. His wife, ABC’s Deborah Roberts, talked about what his weight loss has meant to their relationship and sex life. And Roker confessed about the time he was at the White House after his gastric bypass surgery. “You pooped in your pants,” said correspondent Dr. Nancy Snyderman. “I pooped my pants,” Roker concurred.