Rebel Wilson is opening up about gaining weight after her 'year of health.' Experts explain why that's common.

Rebel Wilson is getting candid about the latest development in her health journey, revealing in an Instagram post on Monday that she's recently gained 30 pounds. The personal news comes as a follow-up to Wilson's body transformation as a result of declaring 2020 to be her "year of health" — something the Australian actress says she did for both her physical and mental well-being. The more than 70-pound weight loss that resulted from those efforts made headlines.

"People are so obsessed with it. But I get it," she told Daily Telegraph's Stellar magazine in October 2021. "For the first time in my life I've lost weight and maintained it. So I'm more proud of that fact."

In the years since losing weight, Wilson has become a mom — welcoming daughter Royce via surrogate in 2022 — and gotten engaged to Ramona Agruma. She's also put some weight back on, which she told fans has made her "feel bad about myself."

She's not alone in that experience. Commenting on her latest post, the Pitch Perfect star's fans shared their own experiences with weight fluctuations. And according to Dr. Katherine H. Saunders, obesity medicine physician at Weill Cornell Medicine and co-founder of Intellihealth for metabolic health, it's "extremely common" for a person to experience some sort of weight gain after a drastic weight loss.

"Our bodies have been adapted to be really good at not starving, so weight loss and, more importantly, weight maintenance are very difficult for most people — especially those with excess weight," Saunders tells Yahoo Life. "When we lose weight, our bodies fight to put weight back on because our bodies want to get back to our 'fat mass set point.' This process, which is known as metabolic adaptation, leads to a reduction in metabolic rate and an increase in hunger, cravings and food noise. This has historically prevented starvation, but it also makes losing weight [for those living with obesity] very tricky."

Research has shown that such alterations in the metabolism can lead to an increased appetite, despite having lost weight. However, Saunders points out that susceptibility to weight gain is "highly individual," as is how it happens. "It can happen suddenly and significantly, or weight can increase slowly over many years. It depends on many, many factors, including how someone lost weight, how much weight they lost, their biology, their medical conditions, their lifestyle, etc.," she says.

A person's history with emotional eating — which Wilson has talked openly about — could likely contribute, adds Brenna O'Malley, a registered dietitian and founder of The Wellful.

"We all to some degree engage in emotional eating," O'Malley tells Yahoo Life. "It's one of many coping skills that we have to use. So it makes sense that it's something that would come up if it's a coping skill that someone's relied on heavily in the past. If someone changes their relationship with food or adds other coping mechanisms, there might still be periods of stress where the coping mechanism becomes more prominent."

Wilson has shared that, in the past, she would "reward" herself with chocolate to deal with the attention she was receiving on set. She also noted that she was accustomed to "numbing emotions with food."

In her interview with the Daily Telegraph, she said that her weight loss was largely a result of dealing with those tendencies. "I'm not totally cured. I don't think you can be. But I've learnt to manage it," she shared.

In her Instagram post, Wilson credited stress for her recent weight gain, as she's been busy working on new movies and a memoir. "It's just been a LOT and I've lost focus on my healthy lifestyle," she wrote.

Fans rushed to offer their support in her comments section.

"Sometimes life asks us to put something down in order to pick something else up. Focusing on work and creating something you're proud of is no small feat — you should be very proud," wrote one follower.

"Life is hard and our bodies go through seasons," another comment read. "You're incredible. Give yourself some grace and keep LIVING. Your weight does not define you." That last line is something Wilson herself has said, taking to Instagram in 2022 after gaining a few pounds while on vacation.

Wilson is certainly feeling the love. "I woke up this morning and read all your comments — they bring a tear to my eye," she wrote as an addendum to her caption. "Thanks everyone!"