Weight Watchers is tipping the scales on Wall Street.

Shares of the Oprah-endorsed diet company popped by more than 7 percent in after-hours trading Thursday, to $74.75, as it reported that one million new subscribers signed up during the first quarter — bringing total membership to a record 4.6 million.

At the same time, operating income more than doubled, to $62 million, as revenues grew 20 percent, to $408 million.

The growth comes as the company makes its program less punitive — adding more foods like fish, chicken, and eggs that don’t need to be weighed and measured — and as it relies more heavily on celebrity endorsements.

Its growing stable of celebrities and social media influencers include hip-hop impresario DJ Khaled and New Jersey filmmaker Kevin Smith — self- proclaimed “fat man” Kevin.

About 40 percent of the company’s new members had never tried Weight Watchers before, Chief Executive Mindy Grossman said.

Dieters are sticking with Weight Watchers longer — more than nine months, or 15 percent more than they did three years ago.

“We don’t see Weight Watchers as a program you choose for a few months,” Grossman said. “It’s a continuous journey.”

While most diet companies get their biggest boost in the first quarter of the year, Weight Watchers is launching a summer marketing campaign for the first time.

The company’s shares are up 200 percent in the last year, far outpacing the 10 percent rise in the S&P 500.