An extreme, all-or-nothing fitness regimen is going viral again as millions seek rapid weight loss and mental toughness through its relentless daily rules. But as health experts warn the intensity may be unrealistic for many people, lighter versions of the challenge are also picking up steam.

Fueled by social media buzz and dramatic celebrity transformations, the viral 75 Hard challenge, created in 2019 by entrepreneur and podcaster Andy Frisella, requires participants to follow a rigid lifestyle regimen “without compromise.”

The rules include two 45-minute workouts each day — one outdoors — a strict diet with no cheat meals or alcohol, a gallon of water daily, 10 pages of nonfiction reading and a daily progress photo. Miss a single task in the 75 days, and the challenge resets to day one.

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“The mental changes are 100x greater than the physical changes,” Frisella says on the challenge’s website. “This isn’t another temporary Band-Aid program,” he promises.

Supporters say the program builds discipline and accountability and has given many participants a clean slate at the start of the new year.

Experts, however, warn that extreme doesn’t always mean effective, especially for long-term weight loss and health.

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“Any program that promises weight loss needs to take you into a calorie deficit,” said Dr. Milica McDowell, a Montana-based exercise physiologist and doctor of physical therapy. “If you are burning more calories than you are consuming, yes, you will lose weight.”

But she cautioned that the results often don’t last.

“The challenge with the 75 Hard workout is that when you stop doing it — which would mean burning fewer calories — and you do not change your eating and drinking behaviors, it is likely that whatever weight you lost during the challenge will come right back,” McDowell told Fox News Digital. 

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“I do not consider this to be a sustainable way to lose weight,” she said.

The Cleveland Clinic also says the program’s rigid, two-a-day structure may do more harm than good for people without a strong fitness base, particularly those with chronic medical conditions. Even drinking a gallon of water a day may be excessive for some people, depending on body size and health needs, it notes.

Medical professionals also urge caution for people with joint or heart problems, no exercise background, a history of eating disorders, or already demanding schedules.

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For those drawn to 75 Hard’s structure, experts suggest modifying the program to suit individual needs.

Variations like “75 Medium” and “75 Soft” have emerged that dial down the intensity with fewer workouts, more relaxed diets and simpler habit targets designed to be more sustainable.

“A softer start lowers the activation energy for behavior change [and] reduces all‑or‑nothing thinking,” Fatima Cody Stanford, an obesity medicine physician scientist at Massachusetts General Hospital and Harvard Medical School, told USA Today.

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The approach can reduce the risk of injury, exhaustion and people quitting altogether, Stanford said.

“I think people are realizing it’s OK to be gentle with yourself,” Morgan Manning, a 26-year-old media and marketing professional from New York City, told USA Today. 

Her TikTok video announcing she was trying the “soft” version received over 60,000 views.

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“These versions feel more human,” said Jesse Ramos Jr., a certified personal trainer and owner of BBT Fitness NYC. “They allow people to build discipline without burning out, getting injured or hating the process,” Ramos told Fox News Digital.

“Fitness shouldn’t feel like punishment,” he added.

Experts agree that consistency matters more than intensity when it comes to long-term weight loss and health.

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Robin DeCicco, a certified holistic nutritionist from New York City, previously told Fox News Digital that she encourages clients to focus on sustainable habits like simply moving more, eating more whole foods and drinking more water than they were before, rather than following rigid rules.

“Healthy habits that change into long-term behaviors are what make people healthier into the future,” DeCicco said.

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A new study from Chalmers University of Technology in Sweden, along with Oslo University Hospital in Norway, may have discovered a way to detect biomarkers of Parkinson’s disease in the blood up to decades earlier.

In the very early stages of the disease, the body goes through changes related to DNA repair and stress in cells. These changes leave detectable clues in the blood before major brain damage occurs, according to a press release for the study.

This could allow for early detection of Parkinson’s, when treatments might have a better chance of slowing or preventing serious damage.

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The processes of DNA repair and cellular stress response can occur for up to 20 years in Parkinson’s patients before motor symptoms fully develop, according to the researchers.

The team used machine learning to discover patterns linked to these processes, which were not found in healthy individuals or patients who were already diagnosed with Parkinson’s.

Annikka Polster, assistant professor at the Department of Life Sciences at Chalmers who led the study, suggested in a statement that the study has found an “important window of opportunity” in which the disease can be detected “before motor symptoms caused by nerve damage in the brain appear.”

“The fact that these patterns only show at an early stage and are no longer activated when the disease has progressed further also makes it interesting to focus on the mechanisms to find future treatments,” she added.

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Polster confirmed that the study highlighted biomarkers that “likely reflect some of the early biology of the disease,” which “paves the way for broad screening tests via blood samples: a cost-effective, easily accessible method.”

The findings were published in npj Parkinson’s Disease.

The researchers plan to further develop tools to more easily detect these active mechanisms and understand how they work, according to the university.

The team predicts that, within five years, blood tests for early Parkinson’s diagnoses could become more common within clinical practice. They are also optimistic about the development of new drugs to prevent or treat the disease.

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“If we can study the mechanisms as they happen, it could provide important keys to understanding how they can be stopped and which drugs might be effective,” Polster said. 

“This may involve new drugs, but also drug repurposing, where we can use drugs developed for diseases other than Parkinson’s because the same gene activities or mechanisms are active.”

Study limitations  

The researchers acknowledged that the study had some limitations, including that the gene activity measured in the blood only partly matches what’s happening in the brain.

External factors, such as medication use, may have affected the results, they added.

Also, the study population may not represent all people, so findings may not apply broadly.

By the numbers

More than 10 million people around the world are estimated to be living with Parkinson’s disease, according to the Parkinson’s Foundation. About 90,000 people in the U.S. are diagnosed each year.

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Numbers are expected to continue rising because Parkinson’s is the second-most common neurodegenerative disease after Alzheimer’s.

While research is advancing, there is no cure for the disease, although medications are available to manage symptoms.

Common motor symptoms include tremors, slowed movement, muscle stiffness, balance and walking difficulties, a shuffling gait and freezing episodes. 

Non-motor symptoms include loss of smell, sleep problems, constipation, fatigue, depression or anxiety, speech and swallowing changes, cognitive slowing and reduced facial expression, according to Parkinson’s Foundation and Mayo Clinic.

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Danish Anwer, a doctoral student at the Department of Life Sciences at Chalmers and the study’s first author, detailed in a statement how Parkinson’s affects the brain.

“By the time the motor symptoms of Parkinson’s disease appear, 50% to 80% of the relevant brain cells are often already damaged or gone,” he said. “The study is an important step toward facilitating early identification of the disease and counteracting its progression before it has gone this far.”

“By the time you have actual motor symptoms … a large majority of affected cells have been damaged and destroyed.”

Fox News senior medical analyst Dr. Marc Siegel agreed that Parkinson’s is a “very difficult disease” with an increasing global impact.

“By the time you have actual motor symptoms affecting gait, tremor, etc., a large majority of affected cells have been damaged and destroyed,” he told Fox News Digital.

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Siegel called the new research “exciting,” suggesting that it “opens the door for earlier and more effective diagnosis and treatment.”

Fox News Digital reached out to the study authors for comment.