Why slave away at the gym when you can go to Club Fed and melt the pounds away like Danielle Chiesi?

The 47-year-old equities analyst, who pleaded guilty to securities fraud in history’s biggest insider-trading case, is back in town, looking fit and trim.

The newly svelte Chiesi was transferred to a federal halfway house in the Bronx last week after serving only 15 months at a West Virginia federal prison for her role in the Raj Rajaratnam case.

“It’s good to be back,” Chiesi told a Bloomberg reporter.

The femme fatale was wearing a white sleeveless peplum top, jeans and pink and white scarf, as she left a residence she shares with other newly freed prisoners on Friday. “I feel good. I feel great,” she added.

The former teenage beauty queen, who once showed up at conferences wearing form-fitting clothes and low-cut tops, is among the most flamboyant defendants to be ensnared in the sweeping federal crackdown.

The probe initially centered on Rajaratnam, the Galleon co-founder who was convicted in 2011 of conspiracy after an eight-week trial.

Rajaratnam, who allegedly earned at least $45 million on tips from corporate insiders, is serving an 11-year prison sentence.