Carolyn Whitson couldn’t believe what the nutritionist was telling her to eat.

Butter, mayonnaise, even steak and eggs.

“I was like, ‘Oh, you’re insane. I’ll weigh 300 pounds if I do that,’ ” said Whitson, 49, of St. Paul.

Reluctantly, she complied. So far, she’s lost 65 pounds by changing her diet and swimming regularly. Even more dramatic was the transformation in her thinking: She no longer fears eating fat. In fact, she embraces it.

For an emerging group of nutritionists, scientists and consumers, fat is no longer seen as the enemy of good health.

For them, the belief that consuming high-fat foods is dangerous is nothing more than a big fat lie. They insist that the inclusion of eggs, cream cheese — even lard — in our diets will make us look and feel healthy.

“No fat, low fat, good fat, bad fat — that’s been the centerpiece of all of our dietary recommendations for half a century,” said Nina Teicholz, author of “The Big Fat Surprise,” a controversial book that contends that the science behind federal guidelines promoting a low-fat diet was flawed. The low-fat food craze, in fact, has led to rising obesity and diabetes rates, and has failed to stem heart disease deaths, Teicholz argues. “Our working hypothesis is not working,” she said.

But there are still plenty of scientists who oppose a high-fat diet. They argue that food science is very complex and they worry about the health ramifications of swinging the pendulum too far the other way.

“The message to consume a low amount of saturated fat has served us well, especially in limiting meat and enhancing plant-based food, but the message was not entirely correct and a new approach is needed,” said David Jacobs, an epidemiology professor at the University of Minnesota.

It was a pioneering scientist from the University of Minnesota whose work fueled the crusade to rid fat from our diets.

Ancel Keys led the famous “Seven Countries Study” in which he examined the eating habits of more than 12,000 men from seven different countries over decades and concluded that those who ate a diet low in saturated fats had lower rates of heart disease. Keys made the cover of Time magazine in 1961 for his findings.

Based in large part on his work, the USDA came out with its first dietary guidelines in 1980 — recommending that Americans remove foods like butter, eggs and lard from their diets because of their high fat content. Soon, products with labels touting “low-fat” and “fat-free” dominated grocery store shelves. Foods like yogurt were stripped of their fats and instead loaded with sugars.

“There was no economic force to counter that, in part because with goodwill, the message was not correct,” Jacobs said.

Even though Keys and other scientists had advocated for reducing saturated fats, the makers of the government guidelines decided that was too complicated and opted for a simpler message to cut back on all fats, he said. That message was “low fat.”

Yet it’s not as simple as just saying that one nutrient is bad or good, Jacobs said. “All in all, there is an answer out there and people are missing it because they’re so obsessed with this framework of ‘If it’s not low-fat, then it must mean high butter,’ ” Jacobs said.

Not all fats are the same. Fats found in avocados, fish and olive oil, for example, have widespread support as part of a healthy diet. Even eggs, which have been in and out of favor with nutritionists over the years, were recently recommended by the USDA officials who removed cholesterol from its list of “nutrients of concern.”

The American Heart Association is among the groups still recommending a diet low in saturated fat.

It’s easy to get confused about what to eat, Jacobs acknowledged, but he offered this simple advice: “There are two words out there: prudent diet and Mediterranean diet.” These are diets high in fruits, vegetables and whole grains. Jacobs added: “Those things seem to capture what people should eat for good health.”

Pass the butter

Teicholz used to be on the low-fat bandwagon.

“I had been your classic female, avoid-all-fat-and-cholesterol vegetarian,” she said. “Like every other woman I knew.”

Gradually, though, Teicholz, a journalist, started reading and researching about nutrition science and completely changed her diet.

She now eats plenty of meat and cheese, and steers clear of bread, rice and starchy vegetables.

“I eat a fairly high-fat diet, like 70 percent fat,” she said. For breakfast she swapped out her cereal for bacon and eggs. “After I make bacon, I save the grease, which is lard, and cook with that,” she said. “I’m not afraid of those foods.”

Darlene Kvist has been preaching about the benefits of fat in a healthy diet for 25 years.

A nutritionist with Nutritional Weight & Wellness and the host of a podcast with 2 million subscribers, she said people used to be skeptical of drinking whole milk and cooking with butter. But times are changing.

“It has swung around from the idea that fat is the demon,” said.

She said she believes that it’s processed foods and hidden sugar that are really causing the obesity crisis. Processed foods often contain the unhealthy kind of fats — trans fats (which affect cholesterol and heart disease).

Before 1950, people typically ate about 40 percent of their calories from healthy fats — in foods like butter, olive oil and nuts, Kvist said.

“But then we started having manufactured fats — like corn oil and soybean oil,” she said. People stopped using the good fats that could be found in coconut oil and lard.

On her podcast, “Dishing Up Nutrition,” and in her one-to-one consultations with clients, Kvist spends a lot of time teaching people about different kinds of fats and how to incorporate all foods into a healthy diet.

“People need a lot of education. They do. They don’t know how to eat because we’ve had so many mixed messages,” she said.

One of her clients, Whitson, has gone from being “rather horrified” by the suggestion that she eat more fat to becoming a disciple. Since she changed her diet, she has kept the weight off for three years, she said.

What she practices, she said, is that fat is OK in moderation. She’ll cook with butter occasionally but not use five tablespoons of it. And she enjoys one other taboo delight:

“I’ll make chicken salad for lunch — and use real mayonnaise.”