I am using two recently published papers from this year to walk through the current front-line understanding of the carnivore diet (CD). The so-called carnivore or all-meat diet generally refers to a daily diet that includes only animal flesh and completely excludes vegetables, fruit, grains, tubers, and other foods. It is more extreme than a ketogenic diet, since ketogenic diets usually still allow non-starchy vegetables.
Short-Term Effects and Long-Term Risks of the Carnivore Diet
Lietz and colleagues published a scoping review on the carnivore diet in 2026 [1], evaluating the current scientific evidence on its health effects and nutritional adequacy. The researchers analyzed nine human studies published between 2021 and 2025, including case studies, social media surveys, and theoretical meal-plan analyses. These studies were generally short-term observations lasting less than two months.
Despite the many restrictions, the included studies still reported some positive short-term outcomes. Subjectively, participants often reported improvements in overall health, satiety, sleep quality, and physical and mental performance. In clinical markers, some studies observed weight loss, reduced need for diabetes medication, and improvements in inflammatory and metabolic markers such as C-reactive protein (CRP). In addition, specific case series reported clinical remission in patients with conditions such as inflammatory bowel disease (IBD) and vulvovaginal candidiasis. The authors suggested that these benefits may be attributable to the anti-inflammatory effects of ketone bodies, the removal of specific dietary triggers such as sugary foods, refined carbohydrates, and processed foods, or a placebo effect driven by participants’ strong beliefs.
However, the carnivore diet is commonly associated with nutritional deficiencies and imbalances. By completely excluding plant foods, it may avoid the interference of so-called “anti-nutrients,” but it also creates serious nutritional gaps. Analyses of nutrient intake show that the carnivore diet fails to meet recommended intakes for vitamins C and D, calcium, magnesium, potassium, folate, and iodine. In addition, dietary fiber intake is almost zero, while saturated fat intake greatly exceeds recommended upper limits.
From the perspective of long-term health risks, multiple studies have recorded significant increases in total cholesterol and low-density lipoprotein cholesterol (LDL-C) among people following this diet. Elevated LDL-C, extremely high saturated fat intake, and a severe lack of dietary fiber and phytochemicals together increase the risk of cardiovascular disease, type 2 diabetes, and certain cancers. In addition, one case report included in the review specifically documented deterioration in health: the patient developed kidney stones and recurrent gout while following a carnivore diet, and these problems resolved only after stopping the diet.
The review concluded that the current quality of evidence supporting the carnivore diet is very low. Existing data rely heavily on self-reported social media surveys and are limited by small sample sizes, short duration, and lack of control groups. The authors concluded that although the carnivore diet may provide short-term subjective or metabolic benefits, the major risks of nutrient deficiency and long-term chronic disease far outweigh those benefits, so it is not recommended as a long-term pattern.
Long-Term Effects of the Carnivore Diet and the Gut Microbiota
If the review above summarizes short-term effects, another cross-sectional study, also published in 2026, comes closer to examining the long-term outcomes of the carnivore diet. Karacic and colleagues analyzed 10 participants who had strictly followed a carnivore diet for 36 months and compared them with 874 omnivores [2].
In this study, the 10 participants completely excluded vegetables, legumes, fermented plant foods, and fast food. Their core staples were red meat and animal fat, and most also consumed fish, dairy products, and poultry. Supplement use varied: three participants took no supplements, while others used vitamin D, creatine, magnesium salts, omega-3, antioxidants, and other supplements. Although the study lacked direct clinical measurements, questionnaire data showed that carnivore dieters reported very high overall health, with a score of 9.01 out of 10. They also had normal BMI, regular daily bowel movements, high energy, and good mental health.
Regarding the gut microbiota, the study reached a conclusion that ran counter to expectations: the complete absence of dietary plant fiber did not lead to a loss of overall microbial diversity. Compared with omnivores, carnivore dieters actually showed significantly higher Chao1 richness, meaning they had more low-abundance bacteria. The carnivore diet caused a large shift in the microbial community and greatly increased the abundance of certain low-abundance phyla, such as Synergistetes and Desulfobacterota. At the level of specific bacteria, the diet reduced levels of health-associated bacteria such as Faecalibacterium prausnitzii and Bifidobacterium, while beneficial commensals such as Akkermansia muciniphila and Lactobacillus remained stable.
Using bioinformatics prediction models, the researchers observed substantial functional changes in the gut microbiota of carnivore dieters. Positive or neutral changes included significant increases in pathways related to protein fermentation, vitamin synthesis such as vitamins B12 and K, and functional modules associated with improved gut barrier function. However, for unfavorable health indicators, the prediction model showed significant increases in markers of fructose and lactose intolerance, which the authors considered a harmless dietary adaptation, as well as inflammation, cytotoxin production, and constipation through methane production. The latter three were mainly driven by increases in opportunistic pathogens and sulfate-reducing bacteria.
The authors argued that the diet did not appear to cause obvious dysbiosis. They speculated that avoiding ultra-processed foods, refined sugar, and food additives, or possible unknown prebiotic effects in animal foods, may have protected microbial diversity. However, the simultaneous reduction in key beneficial bacteria and increase in inflammatory and cytotoxic metabolic modules raises reasonable concern about potential long-term carcinogenic risk. The main limitations of this study are its very small carnivore-diet sample size, reliance on self-reported questionnaires rather than clinical markers, variation in participants’ diets, and the use of only one stool sample per participant.
Summary
Whether people try the carnivore diet briefly or follow it long term, they commonly report feeling well. This may be partly due to survivor bias: people who feel unwell often find it difficult to continue, so they naturally drop out of observation.
In the short term, the carnivore diet does seem to improve some inflammatory symptoms, such as inflammatory bowel disease and vaginal Candida infection, in certain people. Although research has not yet deeply explored the specific mechanisms, these inflammatory conditions are often closely linked to excessive refined carbohydrates in the gut, which can encourage the growth of fungi or harmful bacteria. Therefore, even without adopting an extreme carnivore diet, simply replacing refined carbohydrates with whole grains may also effectively improve related symptoms.
The carnivore diet almost inevitably causes micronutrient deficiencies, so long-term adherents often need to rely on various supplements. It is worth noting that the carnivore dieters in the studies above generally did not consume processed foods and instead focused on whole foods. If a person eats large amounts of processed meats containing additives, it is probably not reasonable to assume that they would achieve the positive effects observed in these studies.
Nevertheless, long-term research found that after three years on a carnivore diet, participants did not develop “leaky gut,” meaning increased intestinal permeability, and their gut microbiota did not show a one-sided deterioration. Whether this is simply because harmful foods such as refined carbohydrates were removed, or whether other unknown physiological mechanisms are involved, will require more scientific research in the future.
Should someone follow a carnivore diet? In the short term, the carnivore diet may indeed bring rapid health benefits, including weight loss, improved mood, and reduced inflammation over a short period. But using the carnivore diet as a long-term lifestyle is essentially an experiment on one’s own body, using individual physiological feedback to challenge the current mainstream consensus in nutrition and medicine.
Modern medicine and nutrition are not absolute truth, and new research continually proves that some previous assumptions were wrong. But before newer scientific evidence becomes available, we can never know exactly where the errors are. Therefore, betting one’s long-term health entirely on a diet that lacks long-term safety data and is already known to have nutritional shortcomings is clearly a gamble with uncertain odds.
Since short-term health improvements have already been achieved, perhaps the wisest strategy is to stop while things are going well. Enjoying physical improvement while returning at the right time to a dietary pattern supported by stronger long-term evidence is the more responsible way to protect the body.
References
- Lietz A, Dapprich J, Fischer T. Carnivore Diet: A Scoping Review of the Current Evidence, Potential Benefits and Risks. Nutrients. 2026 Jan 21;18(2):348. doi: 10.3390/nu18020348. PMID: 41599961; PMCID: PMC12845189.
- Karacic A, Gregorovic R, Hammer P, Liberati-Prso AM, Krumbiegel C, Moskalenko O, Kralj S, Zeman K, Krpan E, Kamel A, Yoshida M. Long-term adherence to the carnivore diet and its impact on the gut microbiota: a cross-sectional study. Microbiota and Host. 2026;4. doi: 10.1530/MAH-25-0015.
