A man claims his life has changed since he began his caveman diet, chowing down on testicles, raw liver and bone marrow every day.
Brian Johnson, from the US, changed his life around 20 years ago after noticing that his children kept getting ill.
So he decided to cut out all processed foods and began following what he calls the 'Nine Ancestral Tenets', which dictates how he eats, exercises and sleeps.
He has since become known as the 'Liver King' on account of the fact that he tucks into a pound of raw liver every single day and posts regular updates to his TikTok account of him working out and showing off his impressive physique.
Speaking about his decision to alter his family's lifestyle, Brian said: "The more my boys interacted with the modern world, the more severe and abundant their allergies became.
"Time outdoors led to hives. Even interaction with our family dogs sparked shortness of breath, puffy eyes and runny noses.
"The real wake-up call was when one of my sons stopped breathing. We were lucky. We made it to the hospital just in time.
"My wife and I were determined to confront the cause. Never to test our luck again. We did what all parents would do: we tried everything. And that's where our journey began.
"First, we eliminated processed foods. We began to reintroduce the nutrition of our ancestors: seasonal fruits and vegetables, nose-to-tail animals including the most nutrient-dense part of all. The liver.
"Within just two weeks, we saw radical change in our boys' wellbeing. Our own too.
"Two decades later, I eat a pound of liver every single day."
Brian's Nine Tenets are:
This is all about optimising your rest, eating your last meal a few hours before going to bed and making sure you're not distracted and using your phone.
Brian goes on three 30-minute walks every day, come rain or shine, and swears by it.
He says: "The well-being that builds from balanced movement trumps the need for consumption based satisfaction."
This is all about protecting yourself from the alleged dangers of modern world, such as WiFi and fluoride.
"Dangers like these end up compounding and with an additive effect, they disrupt our hormones, metabolism and ability to get deep sleep," he says.
Getting rid of high fat and high sugar processed foods, liquid calories and seed oils from your diet.
Brian tries to get as much mid-day vitamin D as he can every day, which he says works with the "fat-soluble vitamins A and K" found in liver and bone marrow.
The 'Liver King' says it's vital he exposes himself to the elements, spending prolonged periods of time in ice baths, rivers and lakes. He says it helps with his circulation and builds up his body's defences.
Don't worry, this isn't about getting into scraps, but Brian says it's key we always set ourselves challenging goals.
Brian often ditches his shoes and goes for long walks, which he says helps keep him connected to Mother Nature and the Earth. This also has a knock-on effect, he says, for his blood pressure and sleep quality.
"Put away the phones and just spend time with loved ones and friends... we've always needed each other... we still do!"