By Jeannine Stein, Times Staff Writer

Stacy Estrada's reaction was immediate and intense. With hand to mouth, she stared in disbelief at the sight before her: a 300-pound cadaver, dissected lengthwise, showing a thick layer of fat around its midsection and surrounding its vital organs.

"Look at this!" she said, hand still over mouth. "This is all fat!"

"He had a pacemaker," a woman next to her noted, pointing to the small metallic device embedded in his chest. Her voice dripping with irony, she added, "I wonder why."

Body Worlds, the anatomically correct exhibit of plastinated cadavers and body parts, is back at the California Science Center for a return engagement, with new specimens. The first Body Worlds exhibit at the museum ran from July to January and drew about 660,000 visitors to see bodies preserved through a process that replaces body fluids with plastic. The show includes whole skinless bodies placed in lifelike poses, or dissected to illustrate the inner workings. Various body portions show bone, nerve, muscle and arteries.

German anatomist Gunther von Hagens created the exhibit to educate the public about the inner workings of the human body and to warn of the consequences of not taking care of it. The first show featured a set of blackened smoker's lungs, and the current one, which runs through March 27, includes a shriveled, cirrhosis-ravaged liver.

It also houses "Suicide by Fat ? Obesity Revealed," an element of the exhibit with a not-so-subtle message about the deleterious effects of excess weight. While the majority of the bodies donated reveal no hint about how the people died or at what age, this one does. A small plaque reveals that the man, who now lies in pieces on a mirrored table, died at age 50 from "malfunction of the heart." He had an enlarged spleen, a fatty liver and so much flab that it draped off his body like spilled pudding.

Adults and children who filed by the exhibit did little to hide their consternation as they reacted with furrowed brows, shaking heads and an occasional "Oh, my God." Everyone has seen an overweight body, but seldom from the inside. For many, it was a wake-up call.

"I'm just amazed at how this person was being squished by his fat," said Estrada, a 19-year-old college student from Covina. "This is a person trapped inside his fat. No more fast food for me, that's for sure."

"I'm grossed out, but I can't not look," said 29-year-old Aurora Romero, a drafter from Long Beach. "It's interesting to see all that fat. But I can't look at it very long." The upshot of all this? "It makes me want to lose weight really badly," she added.

Throughout the afternoon there was much swearing off of bad food and many promises to exercise regularly. For some, it was reinforcement of healthier lifestyles already adopted.

"I saw 'Super Size Me' last year, and I haven't eaten at McDonald's since," said Gus Rios, referring to the documentary chronicling the ill effects of eating nothing but fast food for a month.

Rios, 34, who was at the exhibit with his 10-year-old son, Alex, added, "I'm trying to be more healthy, and I've been teaching him that it's not fun growing up overweight."

They were the kinds of reactions Von Hagens had hoped for. "I want to address the main health hazards and killers which shorten our life span," he said by phone from his hotel room in China.

He said he made an exception to reveal the obese man's age and cause of death because "in his case, the cause of death and his plight in life were so much connected to his anatomy."

Von Hagens wanted to include obesity in the first Body Worlds show, which debuted in Osaka, Japan, in 1995, but he said it took him 15 years to come up with a polymer that mimicked the thick, whitish look of human fat. Without that, he felt, the true damage caused by being overweight might not come across.

But Von Hagens will never know how many people really do swear off chili cheese fries after seeing "Suicide by Fat."

Despite countless public service messages and media reports of the danger of obesity, numbers in the United States and around the world continue to climb. He's hopeful, though; the damaged lungs of a smoker featured in the first Body Worlds seem to have made an impression.

"I have people reporting to me that they've stopped smoking or reduced their smoking, or had some relatives who stopped," he said. "Many people ask me, 'Why do you show real specimens and not models?' Nothing is more convincing or changes our lives more than real experiences. More than ever now we get our information indirectly, but this is direct ? it's real exposure."

Dr. Bill Hanes, an orthopedic surgeon from Covina who visited the show with his children, ages 11 and 15, said he wished that exposure were greater, because seeing the actual effects of obesity might encourage some to lose weight.

"I think this should be shown just about everywhere," he said. "I have a number of overweight patients who come in saying, 'My back hurts' or 'My knees hurt.' Well, the body is not designed to carry that much weight. I have had patients who have lost 30, 50 pounds, and they feel so much better. That's why.