What Happens to Your Body When You Eat an All-Meat Diet?

In grade school, we learn about carnivores, herbivores, and omnivores. Carnivores eat meat; herbivores eat plants; omnivores eat both. Humans are omnivores. Our bodies run on a bevy of amino acids, vitamins, and minerals from many sources.

But in the past few years, interest in an all-meat or carnivore diet has skyrocketed, perhaps influenced by Joe Rogan’s January 2020 stunt where he only ate meat for a month or Australian body-builder Brian Johnson’s raw meat diet, both of which gained considerable views. Since then, the carnivore diet has been gaining steam on numerous social media platforms, especially as a weight loss tool. However, experts Inverse spoke to say a diet of exclusively meat is associated with a number of risks to human health, lacks essential nutrients, and might not even be a good tool for weight loss.

What does an all-meat diet do to your health?

Since you’re eliminating carbohydrates, you will probably drop weight fairly quickly, according to Marie-Pierre St-Onge, a professor of nutritional medicine at Columbia University’s Institute of Human Nutrition. That’s because the high-protein fare fills you up quickly, leaving little room for much else. Further, because carbohydrates are typically a main source of calories, eliminating them altogether will likely result in a caloric deficit, typically a big one.

On top of this, while meat and animal byproducts are chock full of protein and fat, they lack vitamins and minerals that only plants provide. They also lack dietary fiber, which helps keep the gut healthy and moving regularly. Christopher Labos, a cardiologist at Kirkland Cardiology and an associate science communicator at McGill's Office for Science and Society, tells Inverse that the first thing someone who starts eating only meat may feel is “very constipated.” While this might not be an immediately pressing medical issue, it’s still “disruptive and uncomfortable.”

Red meat will also take a toll on heart health. Labos says that red meat provides most of a diet’s cholesterol, which is key to increasing the risk of heart disease. Red meat also increases triglycerides, which are another kind of fat in your blood. According to the American Heart Association, high triglycerides combined with lots of low-density lipoprotein (LDL) cholesterol and not a lot of high-density (HDL) lipoprotein cholesterol increases your risk for things like heart attack and stroke. LDL contributes to the buildup of fatty plaque in the arteries. He adds, that “irrespective of your cardiovascular benefit, eating red meat regularly increases your risk of colorectal cancer.” Numerous studies over the past several decades have concluded that red meat increases a person's lifetime risk of colorectal cancer.

What is meat missing that plants have?

Of course, there’s plenty of other meat besides red meat. Labos calls chicken “the healthier choice” than red meat, and fish is “even healthier.” But St-Onge emphasizes that whether you’re going for fish, chicken, or cow, you’re still not getting vitamins and minerals from plants. Water soluble vitamins, which get absorbed into your bloodstream, help brain and immune function. Some, like vitamins B1, B2, B3, and B5, can be found in both plants and animal products. But others, like vitamin C, only come from vegetables.

A long-term consequence of foregoing those nutrients is scurvy, which you probably don’t have to worry about “unless you are a 19th-century British sailor who has eaten nothing but sea rations for months at a time,” Labos says. But without fruits and veggies, you could become vitamin C deficient. Vitamin C boosts antioxidants, lowers blood pressure, and improves immunity.

Even if you’re on the carnivore diet and take plenty of supplements so you don’t get scurvy, St-Onge counts the many things supplements won’t fix: too much protein, too much fat, higher cholesterol — not to mention the environmental impact and social consequences a carnivore diet could have. “A lot of our social interactions revolve around food,” she says. “If you're just eating meat, then that becomes a little limiting.”

Labos also mentions the “disease of kings:” gout.

Gout is a kind of inflammatory arthritis that creates swelling and pain at the joints, beginning in your big toe. This condition is caused by excess uric acid in the blood, which can create painful crystals around the joints. Animal proteins are high in purines, which are chemical compounds broken down into uric acid when metabolized. During the Middle Ages, only royalty could afford meat, but they ate it in such excess that they sometimes developed gout. Now that meat isn’t only reserved for monarchs, anyone who eats too much of it, or is at an increased risk, can get it.

Labos and St-Onge don’t recommend the carnivore diet for anyone. St-Onge says that if you must try it, don’t continue for more than a few days. She sees this diet as a genuine though misguided effort to improve health. “I would think that someone who wants to do this is thinking about their health, but going about it in the wrong way.” She adds that considering environmental and monetary costs is also important. Raising food animals, especially cows, contributes considerably to emissions. Meat products are overall more expensive than plants, too.