KIRKWOOD, MO—Len Stavros, 46, is a whole new man since he began dating new mistress Amanda Broder, sources reported Tuesday.

Stavros with his supportive, nurturing mistress.

"I can't tell you how good Amanda has been for him," friend Robert Risser said. "He's completely changed. He's calmer, friendlier, and just generally more positive about life. I haven't even heard him bitch about his wife in, like, three weeks, and that used to be a daily ritual."

Added Risser: "I haven't seen Len this happy since he was sleeping with that optometrist a few years ago."

Coworkers have noticed a marked improvement in Stavros' mood since he began seeing Broder on the side in August.

"For the last two months, Len has been in unusually high spirits," said Georgia McGlothen, who works with Stavros in the accounting department of Allied Plastics. "I used to dread going to his office for something, because you never knew if you were going to get Dr. Jekyll or Mr. Hyde. But, lately, he's been nothing but smiles. I really hope they secretly stay together."

Those close to Stavros say he's even been taking better care of himself.

"For a while there, Len was letting himself go a bit," Risser said. "But last week, my wife asked me if he'd lost weight. When I asked him about it, he said he's been eating better and running two miles every morning before work. He's even hinted at becoming a vegetarian like Amanda, but he's afraid [his wife] Mary might get suspicious."

According to McGlothen, Stavros has been putting more care into his personal appearance ever since meeting Broder.

"Len's definitely been dressing better lately," McGlothen said. "I always tease him on the days he looks especially nice, because I know he's got a 'lunch meeting' with a special somebody. You should see him blush—it's the most adorable thing in the world."

Friends also admire the way Broder is able to keep Stavros in line.

"Len can sometimes be a little inappropriate in social situations, and Mary always puts up with it," Risser said. "Not Amanda. I was at dinner with them recently, and when Len started to recommend a dermatologist to the waiter, who had a little acne, she hit him really hard on the arm. He didn't even finish his sentence. Len needs somebody who'll call him on stuff like that."

Even those who are unaware of Stavros' extramarital affair have noticed a difference in his demeanor.

"Len's been a real joy to be around lately," wife Mary said. "He used to just mope around the house, watching football in his underwear and stuff, but these days, he's a dynamo of activity. He's even started playing racquetball at the gym every Thursday night. I'm not sure what the change is, but whatever he's doing, he should keep it up."