Can Your Body ‘Forget’ How to Digest Meat?

If you’ve ever taken a hiatus from meat, then decided to dig into a juicy burger at your bestie’s barbecue, you may have felt an indescribable sense of blah—a heaviness in your stomach, sluggish feeling, and maybe even belly woes like nausea or diarrhea.

This has been a topic on Reddit threads, TikTok comment sections, and beyond, where former meat eaters discuss the potential side effects they’ve encountered when  reintroducing it. For some, the fear of getting sick can derail efforts to incorporate meat back into their life: “I want to stop being vegetarian, but scared to throw up after eating meat,” says one TikTok commenter. 

For others, the results are dismissible: “Honestly, I didn’t notice anything weird,” says another TikToker who ate meat for the first time in 10 years. 

It all comes down to a fundamental question: Does your body really forget how to digest meat, or any other food, for that matter? 

Can your body actually forget foods?

“While there’s no scientific evidence that strongly supports the idea that the body forgets how to digest certain foods after prolonged absence, there are some factors that can impact digestion in this scenario,” says Trista Best, MPH, RD, a registered dietitian at The Candida Diet. “Digestive enzymes and the gut's microbiota change and adapt to the individual's standard eating habits.”

This means your digestion of certain foods may be less efficient after a long time. Nixing specific foods for a prolonged period can lead to a lower production of digestive enzymes. “This is because enzyme production is regulated by dietary intake, and when intake changes, the amount of digestive enzymes produced changes as well,” says Best. 

Researchers have seen gut changes happen pretty quickly: In one small 2014 study in the journal Nature, they prepared a plant-based meal plan (rich in grains, legumes, fruits, and vegetables) and an animal-based meal plan (meats, eggs, and cheese) for participants to consume over five days. 

They found that the animal-based meal plan increased the amount of microbes that can survive bile, which helps break down fat, and decreased levels of those that help break down plant-based foods. 

In other words, the participants’ gut microbiomes shifted in less than a week based on what they ate. “However, this is highly reversible and enzyme production often returns to normal rates when the food is reintroduced and consumed regularly again,” says Best.

Plus, if you suddenly ate meat after your last Meatless Monday turned into a meatless month, you still have some enzymes hanging around to digest your food. “The same enzymes used to digest meat protein are also used to digest plant protein, so you would still have plenty of enzymes around to digest meat, even after a long absence,” says Roshini Raj, MD, a board-certified gastroenterologist at NYU Langone and co-founder of YayDay.

Those protein-digesting enzymes include proteases, pepsin, and trypsin, and your body continues to produce them even after you stop eating a given type of protein. 

So what’s *actually* giving you the blah feeling?

While your gut microbiome does change when you shift your eating patterns, it’s more likely that you feel less tolerant of meat after not having it for a while because it’s higher in fat than plant-based dishes. “This can cause feelings of fullness, bloating, or discomfort,” says Dr. Raj. 

The way meat is cooked can also impact how easy it is to digest. For instance, a 2023 study in the Journal of Animal Science and Technology found methods like sous vide can help break down proteins and speed up digestion. 

Keeping your microbiome healthy also comes down to eating a variety of healthy foods and skipping some of the ultra-processed stuff.

“The key is to nourish the beneficial bacteria that support digestion, immunity, and even mood by eating a wide variety of foods such as fiber-rich, plant-based foods like fruits, vegetables, whole grains, and fermented foods,” says registered dietitian nutritionist Dawn Jackson Blatner, RDN, CSSD. “On the flip side, diets high in ultra-processed foods and added sugars can allow less helpful bacteria to take over, potentially negatively impacting overall health.”

While your gut microbiome does change when you shift your eating patterns, it’s more likely that you feel less tolerant of meat after not having it for a while because it’s higher in fat than plant-based dishes.

How to introduce meat back into your diet (if you’d like!)

If it’s been a while since you’ve eaten a certain type of food, like meat, the key is to go slow. “Reintroduce the food gradually, like once or twice a week, to avoid unwanted digestive symptoms,” says Dr. Raj. 

Also aim for smaller portions (Blatner recommends a condiment size to start), building up to full portions over the course of a few weeks to jog your gut’s “memory” gently. 

Basically, jump back into meat the way you would a cold pool of water: Gently, and gradually. Instead of opting for a big burger at your next cookout (however tempting), try mixing a bit of ground beef into your bean bowl, or try one slice of steak to top a salad. Even cooking vegetables in a bit of beef fat can help slowly re-introduce your body to the enzymes.