Experts review the influencer exercise and diet advice you followed in the 2010s

Nine years ago on the banks of the East River in New York City, hundreds of women in activewear were milling outside an exclusive gym.

Located under the Williamsburg Bridge, the queue snaked for blocks around Pier 36 as women clutched yoga mats under their arms, braided each other's hair and excitedly talked about the fitness icon they'd come to see.

The year is 2016, and the women have gathered to work out with Australian fitness influencer Kayla Itsines.

The creator of the Bikini Body Guide ebook is hosting the free pop-up event for everyone who subscribes to her low-calorie, high-intensity lifestyle.

As she walks into the gym, a roar goes up.

Itsines looks bashful as she makes her way on stage, with her washboard abs on display in a hot pink sports bra and her trademark running shorts.

"I feel like I've grown with you guys," she says into her headset mic.

"I don't feel like it's me standing up here, I feel like it's us — together working out."

"We love you!" a woman screams from the audience.

Itsines smiles.

"I love you guys, too."

A phenomenon

The Bikini Body Guide was eventually rebranded to Sweat with Kayla and reportedly netted the personal trainer $400 million when the app sold in 2021.

It recommended a diet accompanied by high intensity interval training, and attracted thousands of customers.

Despite its popularity, it was not the first of its kind and was not the only ebook in the health and fitness market aimed at young women.

Bikini model Ashy Bines published a 7-week and 12-week program in the early 2010s, and health and wellness advocate Sarah Stevenson — better known as Sarah's Day — followed suit with an ebook called Sweat It to Shred It and YouTube content around her diet.

All three guides featured images of the women in activewear showing off toned stomachs and skinny arms, with promises to help the average woman lose weight and "feel good".

The three women were titans of the social media age, and aside from their guides, slowly turned their success into more ebooks, cookbooks, YouTube videos, apps and more.

However, with their success has come scrutiny.

Asking the experts

The ABC provided the guides and advice content to five sports, dietician and nutrition experts for review.

They include:

They looked at the contents of Kayla Itsines, Ashy Bines and Sarah's Day nutrition and exercise guides, as well as some of their social media content.

"While there were some differences in the content, they were all very focused on weight loss and achieving a certain type of kind of thin body," Dr Denniss said.

"The information seemed to suggest that everyone can achieve a particular look or a particular body type if they simply had enough willpower to follow the guidance.

"We just know that that's simply not the case."

Trigger warning

The behaviours recommended by all three influencers in the original editions of their fitness and health guides have been flagged by both the Butterfly Foundation and InsideOut Institute.

Because of the risk associated with their advice, it cannot be repeated here.

Both eating disorder organisations told the ABC media outlets must be cautious when reporting about disordered eating and exercise.

They warned against reporting metrics like calories or kilograms.

Restrictive or obsessive diet and exercise information, images of underweight people, and any advice which involves "cutting out" entire food groups was also deemed unsafe.

Butterfly Foundation clinical program manager Grace Collinson said diet culture was particularly normalised and celebrated in the early 2010s.

"At that time, it was unlikely that people recognised that much of the information and advice was actually harmful, restrictive and contributing to body dissatisfaction," she said.

"People were yet to find the tools and knowledge to push back against a system that only exists to profit from our insecurities."

While Itsines, Bines and Sarah's Day have all pivoted their content in recent years to focus more on holistic approaches to food and exercise, Ms Collinson said there was a real risk the harm had already been done.

"Research shows that diet culture is particularly harmful and is a significant risk factor for the development of eating disorders," she said.

Diet and nutrition

Here's what the guides and content had in common when it came to offering nutrition advice:

"If someone were doing both the exercise and the food guides and they were following both to the letter, I would expect them to be feeling pretty hungry," Dr Denniss said.

"I would think that it could potentially also lead to the development of an unhealthy relationship with food."

"Any time that there's advice to reduce or cut out core foods, that's always a really big concern of mine."

Dr Denniss said food being branded "good" or "bad", advice on eating out in restaurants and cutting out certain things that make healthy foods palatable also did not sit well with her.

"Food is not simply energy and nutrients," she said.

"There is also room in the diet to consume things that you know are maybe high in fat and salt and calories on occasion."

UWA professor Amanda Salis said she had varied opinions on the guides, and found Bines' information the most harmful.

"My overall impression of this guide is that it — and other programs like it — can lead to problems for people in the long run if they believe the information," she said.

"Moreover, in several places the guide asserts ideas that are contrary to scientific research on nutrition."

She said it was unhelpful to "vilify" types of foods, and it could encourage "all or nothing" type thinking.

Dr Salis said in contrast, she thought Itsines guide was well-backed by science.

"The Kayla Itsines program … had appropriately trained health professionals overseeing the content of the program," she said.

Dr Salis, who runs clinical weight loss trials, said the impact of the advice would often rely on a reader's health literacy and level of vulnerability.

Exercise

Here's what the guides and content had in common when it comes to exercise.

The guides often recommend exercises like burpees, commandos, jump squats and jump lunges.

Dr Ben Singh said there were definitely positives.

"Research consistently shows that HIIT can produce significant fitness improvements in shorter periods than traditional steady-state cardio, which appeals to those looking for quick, efficient workouts," he said.

Dr Singh said while the guides had done good work in popularising fitness among young people — including making it more accessible and motivating — there were also downsides.

"For the average person, particularly those without a consistent exercise background, the intensity of the program may be challenging," he said.

Dr Singh said overtraining was also a risk, with some guides failing to include adequate information about rest, recovery and injury prevention.

"These programs have participants work up to a minimum of six days of exercise per week," Dr Singh said.

"For most people, this is simply not required to improve health and fitness."

He said he was also concerned by how it could impact the body image and self-perception of its target market — young women and men, who are historically more at risk of developing eating disorders.

"The strong focus on achieving a "lean, toned" physique and "burning stubborn fat" might inadvertently reinforce societal pressures to meet specific aesthetic ideals," Dr Singh said.

He particularly noted concerns around the phrasing used by Ashy Bines and Kayla Itsines around "bikini bodies".

"The focus on aesthetics can create unrealistic expectations," he said.

"Promoting diverse motivations — like stress relief, strength, and improved energy — could help build a more positive relationship with exercise."

How much harm has been done?

Experts said the public is getting better at seeking out science-backed nutrition and exercise information, and influencers were also evolving their content accordingly.

Dr Singh said it would be helpful if more influencers were open about how their approaches had changed over the last 15-years.

"As understanding of health, fitness, and body image has progressed, it may be valuable for influencers to reflect on their past content and consider how their messages align with current evidence-based approaches," Dr Singh said.

Dr Denniss agreed.

"I think that individuals do have a responsibility [to reflect on past content], but I think they're often the scapegoats," she said.

"We really like to, as a culture, demonise these influencers when really, if we're going to hold anyone to account it should be the wellness industry, the weight loss industry, and also social media platforms that propagate imagery and information that we know to be harmful."

What did the influencers have to say?

The three women were asked the same questions by the ABC.

• Does you accept you contributed to harmful diet and fitness culture in the mid 2010s? If so, what do you have to say to this? If not, why not?
• How do you respond to people who claim your fitness and nutrition guides did lasting damage to their relationships with food and exercise?
• What have you learned over the last 15 years that now informs your programs and business?

Sweat by Kayla Itsines declined to comment.

Sarah's Day did not respond to multiple requests for comment.

Ms Bines team provided the following statement: