Ms Lewinsky said despite her desire to return to a more private life, she had joined forces with Jenny Craig because she found it worthwhile - and because of pressing legal fees.
Ms Lewinsky, who was at the centre of President Bill Clinton's impeachment scandal, has lost 14 kg (31 lbs) since last summer.
She was reportedly offered $1m if she slimmed down another 7kg (15 lbs).
"I feel good. I feel better about myself, but I don't think I'm quite ready to wear a bikini yet," said 26-year old Ms Lewinsky.
Commercials featuring testimonials from Ms Lewinsky had a five-week run in January and February.
Some privately-owned Jenny Craig franchises, criticising the selections as inappropriate, kept running older adverts rather than using the Lewinsky campaign.
Denial
The company denied they were dropping Ms Lewinsky because of her weight, citing a policy of using non-celebrity models.
However, Patti Larchet, Jenny Craig's chief operating officer, said the company might consider "revisiting" Ms Lewinksy if she lost another 5kh-7kg (10-15 lbs).
When she started the campaign, Ms Lewinsky noted the irony of appearing in advertising material while trying to escape the spotlight surrounding her affair with President Bill Clinton, which led to his impeachment trial.
Ms Lewinsky said despite her desire to return to a more private life, she had joined forces with Jenny Craig because she found it worthwhile - and because of pressing legal fees.
"I hope that people don't see it as a double standard. I'm in a position right now where I'm trying to support myself and pay my legal bills, and so I'm looking for kind of the best way to do that," Ms Lewinsky said, in a CNN interview with Larry King.
Jenny Craig posted a net loss of $7.6m last quarter and announced plans in November to trim 15% of staff at its headquarters.