Weight Watchers Int'l   (WTW) announced this afternoon that it appointed Mindy Grossman as President and CEO effective this July.

She will also join the company's board of directors.

Grossman joins Weight Watchers from HSN (HSNI) where she served as CEO since 2008.

"I am thrilled to join Weight Watchers and lead the next phase of the Company's transformation. This is a tremendous opportunity to leverage technology and consumer insights to create innovative personal experiences, build loyal communities and accelerate growth," Grossman said.

Shares of Weight Watchers closed higher over 7% today on heavy trading volume of about 2 million shares vs. the monthly average of roughly 1 million, and have extended their gains in after-hours trading climbing over 11% on the report. 

(What will move markets this quarter and how should investors position themselves ahead of time? Jim Cramer sat down with four of TheStreet's top columnists recently to get their views. Click here to listen to his latest Trading Strategies roundtable with them and read their advice for stocks, bonds, forex and gold.)