The former Playboy model, 55, recently shed 25 lbs. while participating on Bravo's weight-loss show, Thintervention with Jackie Warner.
And now that she has a svelte new figure, Keough is seeking opportunities to show it off in a bikini. "I'm thrilled," she told PEOPLE about slipping into a two-piece. "I always thought I'd lose weight and then go get liposuction or something, but I never did. I'm as hard as a rock."
The reality star and mom of three, who recently treated herself to "a bunch of new dresses," hasn't completely cut out her guilty pleasures. "I still love pizza," she says. "I just limit myself to two pieces once a month."
Keough also refuses to give up alcohol, but she's changing her preferences. "I loved drinking red wine, but Jackie's pretty much convinced me vodka or tequila with some fresh lime in it is a better route to go," she says.
Keough, who spent three hours a day commuting back and forth from Orange County to Los Angeles during filming for Thintervention, says she still works out four or five days a week. She's also made other lifestyle adjustments in addition to becoming more active.
"I eat every three or four hours," she says. "I have to think more and take more time to be prepared and have food with me, so I don’t get to a place where I'm just starving and have to have pizza right now."
The Thintervention finale, which will feature the weight-loss of Keough and her costars, airs Monday on (10 p.m. ET) Bravo.