What really happens to your body when you give up meat—even just briefly

Going meat-free for just a few weeks can trigger surprising changes, from gut bacteria shifts to lower cholesterol. But the key to reaping the benefits isn’t just what you cut out—it’s what you add in

A variety of nutrient-rich plant foods, from leafy greens to legumes, offer essential vitamins and minerals. Experts say swapping meat for fiber-packed vegetables and whole grains can lead to improved gut health and lower cholesterol.

Whether for health, environmental concerns, or ethical reasons, more and more people are opting to cut meat from their diets. But what happens to the body when meat or animal products disappear from the plate?

Recent research suggests that even short stints without meat—whether weeks, days, or even just a few meals—can trigger surprising changes. The effects range from weight loss and signs of heart health improvements to more subtle impacts on the gut and immune system.

Weight loss and heart benefits

One of the most noticeable effects of cutting out meat is weight loss, but it’s not just about removing animal products—it’s about what takes their place. When people replace calorie-dense meats with fiber-rich plant foods like vegetables, legumes, whole grains, and fruits, “we end up just consuming more foods that are fewer calories,” says Matthew Landry, a registered dietician and health scientist at the University of California, Irvine. Fiber-rich foods also help us feel satiated for longer, which can reduce overeating.

For instance, a 2018 study tracking people over three months found that those who shifted from an omnivorous to a vegetarian diet lost roughly 4 pounds.

The benefits extend beyond weight. Several studies have found that vegetarian diets lasting six weeks or more can lead to lower blood pressure, a key factor in reducing the risk of heart disease and stroke. This effect is likely linked to weight loss and greater consumption of minerals like potassium and magnesium that help reduce blood pressure, says Luigi Fontana, an expert on nutrition and healthy aging at the University of Sydney. Vegetarian diets often also lower blood sugar, reducing the risk of developing type 2 diabetes, according to a recent review by Fontana and his colleagues.

(Want a better high-protein diet? You don’t have to eat more meat.)

Other studies on vegetarians have seen drops in low-density lipoprotein (LDL) cholesterol—the “bad” cholesterol abundant in meat and dairy products that clogs up blood vessels and raises the risk for heart disease and stroke.

A study on 11 pairs of twins, led by Landry and his colleagues at Stanford University, found that those who followed a vegan diet saw their LDL cholesterol drop to optimal levels below 100 milligrams per deciliter after four weeks. Even though participants started with relatively healthy levels, the decrease was still notable.

Changes in the gut

Switching to a plant-based diet doesn’t just change what’s on your plate—it can alter the ecosystem of bacteria living in your guts. New vegetarians tend to develop more bacteria specializing in chopping up fiber in plant-based foods, and fewer bacteria that target meat, explains Veronica Witte, a neuroscientist at Germany’s Max Planck Institute for Human Cognitive and Brain Sciences and the University of Leipzig Medical Center. In a 2014 study that used stool samples to analyze the gut bacteria of people who shifted to a plant-based diet, the makeup of their gut bacteria changed, “even after several days,” says Witte.

Although the precise effects aren’t consistent across studies, some changes may be beneficial. Preliminary data from the Stanford twin study found that Bilophila wadsworthia, a gut bacterium that chops up specific proteins in animal products and has been linked to disease-driving inflammation, declined in the twins who went vegan. It seems, “that B. wadsworthia can be very problematic to have in your gut microbiota at high abundance, and one way to help get rid of this microbe is to switch to a vegan diet,” says co-author Matthew Carter, a microbiologist at Stanford.  

Scientists are also investigating the potential benefits of fiber-fermenting bacteria and possibly harmful effects of meat-processing ones. Meanwhile, Witte is investigating whether changes in gut bacteria can somehow affect the brain and influence food cravings. But, she cautions, we need more research “to really show that these [processes] are at play.”