By Vicki Sheff-Cahan
Updated July 09, 2007 12:00 PM

What have the past 18 months been like for Kristy Swanson? As the actress—still best known for 1992’s Buffy the Vampire Slayer—curls up on the couch in her three-bedroom Los Angeles apartment, she answers with one word: “Stressful.”

Yeah, battling the undead might be a breeze in comparison. Since falling for her Skating with Celebrities partner, two-time Olympian Lloyd Eisler, Swanson has coped with unflattering coverage of their relationship (when it began, Eisler’s then-wife was eight months pregnant) and then an arrest last month for allegedly attacking Eisler’s now-ex, Marcia O’Brien. Meanwhile, her weight has ballooned—the first 20 lbs. piled on in the early days of the romance (“I stopped skating and we were eating all of these wonderful antipasti with cheese and crackers,” she says), before pregnancy left her at nearly 200 lbs.

Now mother to 4-month-old Magnus (“I don’t have a nanny—I want to be a hands-on mom,” she says), the 5’6″ Swanson is back down to 155 lbs. “The heaviest I’ve ever been!” she groans. Which is why she has signed a six-month, six-figure ad-campaign deal with Medifast, hoping to lose 30 lbs. and drop from a size 10 to a size 6. (Despite her arrest, Richard Zeeb, a Medifast marketing exec, says, “We stand behind Kristy 100 percent.”)

As for what she hopes to gain, peace of mind is at the top of her list—and not just about her body. Disputing the label put on her in various accounts, Swanson, 37, insists, “I’m not a homewrecker,” adding, “Lloyd and Marcia were separated before I ever met him; I did not break up the marriage.” Eisler, 44, says, “We got to know each other over time. After the show was over it hit me, ‘Wow, that person had a drastic effect on me!’ Changes had to be made—and I chose to make them.”

Nonetheless, tensions flared over Father’s Day weekend when Eisler, 44, and Swanson, 37, headed to O’Brien’s home in Kingston, Ont., for a visit with his two sons—Ethan, 3, and Seth, 18 months. (Eisler’s divorce was finalized in January.) Following a 911 call from O’Brien, police arrested Swanson, who posted $470 bail; the next day, the actress filed counter-assault charges against O’Brien and insists, “She attacked me, and I am confident that after the investigation is complete, the truth will come out.” (At press time, police had yet to charge O’Brien; for her part, O’Brien says, “Her allegations that I attacked her are completely false.”)

This may not seem an ideal time for a diet, but Swanson says, “I know the longer I wait the harder it will be.” Having spent the last weeks of her pregnancy “eating everything that wasn’t nailed down,” Swanson is now limited to only 1,000 calories a day (most diets allow at least 1,200), comprised of five Medifast “meal replacement” foods—such as powdered scrambled eggs and broccoli soup—and one “real meal” of, say, grilled fish and steamed veggies.

But Swanson is confident she’ll stick to the plan, citing a special motivation: “Once I’ve lost a few pounds and can fit into something,” Swanson says she will walk down the aisle with Eisler, most likely in October. Imagining her wedding gown, she breaks out into a laugh: “Don’t smaller dresses cost less?”