(CNN) Oprah Winfrey revealed this week that she lost more than 40 pounds , and she did it using one of the most popular weight loss programs out there: Weight Watchers.

In a story first published on People magazine's web site , Oprah said she's still eating the tacos and pasta that she loves, and she doesn't feel deprived following the Weight Watchers system. Earlier, she told People that she's exercising more , striving to take at least 10,000 steps a day.

"Weight Watchers is easier than any other program I've ever been on. It's a lifestyle, a way of eating and a way of living that's so freeing. You never feel like you are on a diet and it works," Oprah, 62, said in a release about a new Weight Watchers' ad campaign.

Weight Watchers works by using a point system for people to track calories. Although it dominated for decades, it recently faced challenges from Nutrisystem and free apps and sites designed to track health and weight loss. The company's chief executive stepped down earlier this year.

Still, the company saw a bump earlier when Oprah purchased a stake in the company -- she's the third largest shareholder in Weight Watchers, and has a stake worth about $77 million -- and as she continued to share her weight loss successes. After the announcement this week of Oprah's weight loss milestone and the company's new ad campaign, Weight Watchers shares jumped 17%.

Although the program has evolved in recent years, there's a reason its point system and group meetings have stuck around.

"It's livable," said Dr. Melina Jampolis , a physician-nutrition specialist, who is not in any way affiliated with Weight Watchers said in 2015. "With restaurants and holidays and parties, you have the tools to handle any eating occasion."

History of Weight Watchers

Weight Watchers has been a powerful and effective tool in the fight against obesity since the program was founded in 1963 by Jean Nidetch, a self-described "overweight housewife obsessed with cookies."

1963: Weight Watchers is founded by Jean Nidetch, a self-described "overweight housewife obsessed with cookies."

After struggling to lose weight for years, Nidetch began hosting weekly meetings at her home with friends, to discuss their difficulties with dieting and exercise.

"Compulsive eating is an emotional problem," Nidetch told Time magazine in 1972, "and we use an emotional approach to its solution."

Abiding by her philosophy -- "It's choice, not chance, that determines your destiny" -- Nidetch managed to lose more than 70 pounds, and keep it off.

According to its latest earnings release, Weight Watchers currently has 2.8 million active subscribers worldwide, down from 3.4 million one year ago.

How does Weight Watchers measure up?

Weight Watchers works by using what it calls "SmartPoints," where one number represents each food and drink's calories, saturated fat, sugar and protein.

When US News and World Report ranked 35 of the most popular diets, Weight Watchers tied for fourth place overall -- and No. 1 for weight loss. (The diets taking the No. 1 and No. 2 spots overall were the DASH diet MIND diet and TLC diet.)

U.S. News called Weight Watchers "effective," highlighting the upside that you can eat what you want and that no foods are off-limits. Downsides include the program's price and tedious point tallying.

"It's based in real life, real food, real living," Gary Foster, Weight Watchers' chief scientific officer said last year. "We're not a brand about exclusion, saying 'you must eat this' and 'you can't eat that.' You're in charge of what's in and what's out."

If you restrict eating to certain foods or certain times of the day, said Foster, you might get people to eat less, but the results are short lived. They'll put the weight right back on.

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"Broadly, reality not meeting expectations is what trips people up," said Foster. "The most common example is when people have unrealistic notions of what the weight loss journey will be -- that they'll lose the same amount (of weight) every single week, or eat perfectly every single day. Life gets in the way. Teaching people a different mindset around that and being aware of your thinking style is key. 'All or none' is not good for weight, relationships or work performance."

"The other thing is to not be so myopically focused on the scale," said Foster. "It's a piece of metal that gives you a number and is fraught with disappointment. It's not a good measure in the short term. It's better over the long term. Non-scale victories like looking better, feeling better, fitting into a smaller jean size" are far more important milestones.

The Oprah Effect

On November 15, 1988, Oprah opened an episode of her show titled "Diet Dreams Come True" by revealing her new slim figure. She showed -- not just told -- her audience how much weight she lost by wheeling 67 pounds of fat on stage in a bright red Radio Flyer wagon.

"This has been the most difficult thing I have ever done in my life," Winfrey said. "Those of you who are starting dieting -- this is what 67 pounds of fat looks like. ... It's amazing to me that I can't lift it, but I used to carry it around every day. When you talk about making yourself the best you can be, I'm glad I did this for my heart, because my poor heart had to send blood to all of this. It's shocking to me."

The episode was the highest rated in the show's history.

"Her journey has been so challenging and public with weight," said Jampolis. I think as far as celebrity endorsements go, she has the potential to be more authentic than many, because people know her struggle and because she's not looking for a quick fix."

"Oprah has all the money in the word and she's still had a life-long battle with her weight," said Jampolis. "If anyone can connect with and understand the consumer, it's her."

The future of weight loss

"In the end, weight loss isn't what people are pursuing anymore," said Foster. "People are no longer saying ... 'I want to lose 20 pounds.' They say, 'What I'm after is a healthier, happier life.'"

That is to say, weight is now a metric instead of the only metric.

"Dealing with choice and balance is key to long-term success," said Jampolis. "Just focusing on food is only a small part of the equation. Psychologically, there's more than just being at a healthy weight."

"For most people, they have a really good general sense of what they should do. Everyone knows how to do it -- it's why you don't do it. As a nation, we're self-medicating a lot with food."

When Weight Watchers' partnership with Oprah was announced, Jampolis applauded the broader focus on health and happiness.

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"Most weight-loss doctors and dieticians say it's one of the strongest programs out there," said Jampolis. "There's a lot of positive potential. It's a very good program that could potentially be made better with (Oprah's) guidance."

At the end of the day, you need to feel satiated on a basic hunger level. Beyond that, you need to feel satiated on a more cerebral level, she said.

It's about letting yourself have the food, but more importantly the experiences, said Jampolis. "Happiness comes from sitting around the table with people you care about, enjoying some of your favorite dishes."