And now, the actresses and friends have banded together in a pact to stay just the way they are, RadarOnline.com has learned.
"Rebel and Melissa have known each other for five years and there's a lot of love there," the source said.
"Neither one of them is trying to lose weight and they've formed this little support group to keep each other from falling into the skinny Hollywood trap."
The Super Fun Night and Mike And Molly TV stars, who also act in movies, refuse to succumb to the pressure of the media which is "desperate to see what these hilarious and successful women would look like when they're thin.
"Obviously, they could both snap their fingers and lose the weight because of the resources they have available to them -- which could include everything from personal trainers to Lap Band surgery -- but right now they're agreeing with each other that they have to hold the line and provide a positive image for overweight girls everywhere."
As Radar has previously reported, Wilson has said fans identify with her distinctive look.
And married mother of two McCarthy told The New York Times after veteran movie critic Rex Reed called her a "female hippo," that she "felt bad for someone who is swimming in so much hate."
According to the source, "There will be plenty of time for dieting years from now, but Rebel and Melissa are determined to stay at their current sizes for now."