A cardiologist has issued a warning after a patient was left experiencing bizarre and concerning side-effects after eating a strict carnivore diet.
The man, who was in his 40s and who has not been named publicly, ate "very extreme amounts of fat and protein" for eight months as part of the diet - and soon noticed a strange side-effect on his body.
He would eat up to 6 to 9 lbs of cheese a day, as well as sticks of butter and other fat, along with daily hamburgers, according to Dr. Kostas Marmagkiolis, an interventional cardiologist at Tampa General Hospital, USF Health and Tampa Heart in Florida, who treated him, as reported by Today.com.
He sought medical attention after he suddenly developed yellow lumps on the palms of his hands, mainly along the natural creases.
The yellow lumps were found to be deposits of excess cholesterol under his skin, with tests showing that the man's total blood cholesterol was more than 1,000 mg/dl - way over the healthy limit for adults, which is less than 200 mg/dl - one of the highest results Marmagkiolis had ever seen.
The doctor told Today.com: "This patient was not aware that his cholesterol was that high,” noting that it had previously been at a normal level for several years.
He continued: "Abruptly within one year, his cholesterol dramatically increased, and at the same time, those lesions appeared.
"So we have to assume — based on the history of this patient — that those lesions were directly caused by the high cholesterol, which was directly caused by the type of diet that he was [eating]."
The man had been following the carnivore diet - which involves eating high-protein, no carbs, and only animal products, mainly consisting of meat, eggs and some dairy, and excluding fruits, vegetables and grains - for eight months.
However, registered dietitian Kristin Kirkpatrick warned that as the diet is high in saturated fat, it can raise the cholesterol as well.
A case report in JAMA Cardiology stated that the man had lost weight and reported having more energy and improved mental clarity, but was referred to Marmagkiolis after his primary care doctor noticed the unusual deposits on the palms of his hands.
Marmagkiolis stated that yellow deposits under the skin are a red flag for high cholesterol levels, explaining: "We believe that is a way of the body to eliminate the additional cholesterol from the bloodstream whenever it cannot process it."
The bumps commonly appear on the eyelids, where they are known as xanthelasmas, and when they show up on other body parts such as the hands, elbows, or soles of the feet, they are known as xanthomas.
Not everybody who has high cholesterol will develop these bumps, however, as Marmagkiolis says it only affects around 1% of patients with high cholesterol and is partly down to a genetic predisposition.
The yellow deposits are painless and harmless, but generally don't go away by themselves without being removed by a dermatologist.
The cardiologist noted that the bumps in this man's case pointed to "an amazing amount of cholesterol in his bloodstream,” requiring immediate medical attention.
Doctors advised him to immediately switch to a more balanced diet, as well as to take medication to lower his cholesterol.
High cholesterol can increase the risk of heart attacks and strokes by causing plaque to build up in the arteries, narrowing them, per the National Heart, Lung and Blood Institute.
Increasing numbers of people have been turning to alternative keto diets such as the carnivore diet, as it can make them feel full while losing weight, according to Marmagkiolis, as the lack of carbohydrates forces the body to burn fat for energy instead of glucose.
There are some benefits to the diet, as it eliminates sugar, refined grains, and ultraprocessed food which can cause obesity and lead to Type 2 diabetes, according to Kirkpatrick, but the carnivore diet often leaves people severely lacking in vital vitamins and minerals including magnesium, calcium, and vitamin C, as well as fiber, according to studies.
Removing plant-based foods can lead to nutrient deficiencies, as well as gut issues and constipation from the lack of fiber in the diet.
Generally, doctors advise against following any extreme diets, and instead focusing on a balanced diet containing protein, fat, and carbohydrates, made up of whole foods and less ultraprocessed food.