The 50-year-old former "Seinfeld" co-star is partnering with the firm in an effort to lose 30 pounds.
Alexander recently reprised his character of George Costanza in a "Seinfeld" reunion episode on "Curb Your Enthusiasm."
"I looked at myself playing a character I started playing 20 years ago and yes, he had aged -- but what was disturbing is that he was no longer in a body I cared to recognize," Alexander said in a statement.
The actor admitted he has tried numerous diets and regular exercise to deal with the extra pounds he's been carrying.
"It's always been the same old story -- the first 10 pounds were gone in a jiff, but then: 'Bamm! Back again.' And this time, they're back with a vengeance -- they even brought friends," Alexander said.
"I just got to a point where I didn't think there was a diet or program out there that would work for me," he said. "But I recognize that I need a new relationship with food and that I'm ready to stop talking about it and actually do it!"
Alexander said he hoped he could "be the catalyst for other guys to get moving, too."