Powter made millions with her 'Stop the Insanity!' fitness infomercial in the '90s ... "I've learned that women are invisible and invaluable after a certain age," she says.

If you're starting a workout program that calls itself "Insanity ® by Beachbody," you know it's going to be over the top. This is one of the most challenging fitness programs on the market.

The fitness ... Insanity Radio, and alongside other journalists or producers for research purposes. Since joining Newsweek, Melissa has been especially focused on covering under-reported women's ...