I know it's true because he said so.
Barbara Walters interviewed the Obamas for a 20/20 fluff piece scheduled to air tonight, Friday, December 23rd. When asked on what occasion the POTUS and the FLOTUS lie, Obama, always above the fray, said:
Usually, the only time I lie is very personal interactions with family members, who you say, "You look great," and they don't...
Heads up to family members: You may not be looking as great as Obama said you were.
Heads up to the rest of the country: Obama lies about the big things, too.