Jackson said she is proud that the Nutri-System is committed to donating $10 million in food contributions to the hungry.
Still, research suggests 80 percent of most dieters re-gain the weight on national weight loss plans.
"It is a matter of learning how to keep it off," she said.
It has been a year of a "great deal of happiness, some sadness," Jackson said. In November, the Jacksons were forced to relive the trauma of Michael Jackson's death during the trial of Conrad Murray, who is serving a four-year sentence.
At the time of the conviction, Janet Jackson posted on Twitter, "justice has been served," and she said not a day goes by that she doesn't think about her brother, Michael Jackson.
"Even though it doesn't bring my brother back -- that would be the ultimate -- but the best was done at that moment," she said. "It was difficult for all of us. It wasn't easy sitting there every single day."
But 2011 also has been Jackson's year of new beginnings. Aside from her new spokeswoman role, she has a deal to direct a new film project and an international concert tour. Jackson, who once collaborated with her brother Michael Jackson on many projects, said she wanted her brother's legacy to be how much he loved others.
"His love for children, his love for people, his love for music, his love for the fans -- just love, period," she said.
ABC's Lauren Effron contributed to this report.