The carnivore diet: Health boost or recipe for disaster?

Humans have more dietary choices than ever—everything from plant-based vegan diets to high-protein, meat-focused plans. One of the most talked-about trends today is the carnivore diet, an all-animal approach that includes meat, fish, eggs, and some dairy—but excludes all plant foods like fruits, vegetables, grains, and nuts.

Supporters claim it can help with weight loss, reduce inflammation, improve digestion, and even boost mental clarity. Critics warn it’s too restrictive and may lead to nutrient deficiencies or long-term health risks. So, what does the research actually say—and what does it mean for someone studying nutrition or personal training?

A brief history of the carnivore diet

Although it’s trendy now, meat-focused eating isn’t new. Early humans relied heavily on animal foods, particularly during the Ice Age when plants were scarce. One of the first structured all-meat diets was the Salisbury diet, created in the 1880s. This plan recommended 2–4 pounds of lean beef per day, plus 3–5 pints of hot water, for several weeks. Followers reported weight loss, reduced belly size, and improved well-being (1).

The modern carnivore movement has grown in the last decade, championed by figures like Dr. Shawn Baker, who published The Carnivore Diet in 2019.

What does the science say?

Several studies have been published that help us understand the potential risks and benefits of this radically different approach to human nutrition.

Does the carnivore diet make you deficient?

Research by Goedeke and colleagues (2) modelled four versions of the carnivore diet against national nutrient reference values (NRVs). The results showed that the carnivore diet met the NRV thresholds for several nutrients. These include riboflavin, niacin, phosphorus, zinc, vitamin B6, vitamin B12, selenium, and vitamin A, and exceeded the sodium threshold. However, thiamine, magnesium, calcium, vitamin C, iron, folate, iodine, and potassium were found to be below the NRVs.

Another issue was the lack of fibre, which raises concerns about gut health and long-term metabolic health. Those diets limited to muscle meat and eggs showed significant deficits, especially in vitamin C and folate. The risk of some of these deficiencies was reduced by consuming liver and seafood, which provide broader micronutrient coverage. In light of these results, the authors concluded that a carnivore diet is nutritionally viable under carefully planned conditions. This includes emphasising the importance of organ meats and seafood to prevent deficiencies.

Does the carnivore diet plan provide any health benefits?

Individuals often cite improved health as a key reason for implementing the carnivore diet, but to date, there has been little supporting evidence. To address this, the Harvard Carnivore Study (3) tracked over 2,000 participants who had followed the diet for at least six months. Results showed:

• 95% reported improved overall health
• 66–91% noticed better mental clarity, energy, and sleep
• 48-98% demonstrated improvements in various medical conditions. For example, diabetic individuals experienced improved glycaemic control and reduced medication (84%–100%).
• Average BMI dropped from 27.2 to 24.3 kg/m²

Adverse effects were rare (<6%) and mostly digestive. While LDL cholesterol was elevated, HDL cholesterol and triglycerides remained healthy. Researchers caution, however, that more long-term studies are needed.

Other studies suggest that the diet may help reduce inflammation. Norwitz and Soto-Mota (4) found that patients with inflammatory bowel disease (Crohn’s disease or ulcerative colitis) who adopted the carnivore diet experienced reduced abdominal pain, diarrhoea, and fatigue. A reduction in inflammatory markers was also noted, and several patients were able to reduce or discontinue their use of immunosuppressive drugs. However, as impressive as these results seem, the authors recommend caution as their study was a small, uncontrolled case series. They suggest that randomised controlled trials are needed to establish efficacy and safety.

How does it affect athletic performance?

The carnivore diet has not only gained popularity among individuals wishing to improve their health, but also among athletes and fitness enthusiasts. Yet its restrictive nature, particularly its lack of carbohydrate, opposes the current consensus for sports nutrition.

To explore how the carnivore diet affects athletic performance, Bowser and colleagues (5) studied an 18-year-old female soccer player who followed a strict carnivore diet during a 13-week competitive season. Over 22 matches, researchers tracked her heart rate, movement data, and overall training load.

The results showed she was under more physical stress than her teammates. Her training load score was noticeably higher, suggesting her body was working harder during games. Because of this, she was advised to add a small amount of carbohydrate to her diet—about 16 grams before games and 6–10 grams afterwards.

After introducing carbohydrates, her performance and recovery improved. Her training load dropped below the team average, her average game heart rate decreased, and her work rate and recovery were better overall.

The researchers concluded that adding carbohydrates helped improve recovery, reaction time, and performance. This suggests that it was the lack of carbohydrates—rather than the carnivore diet itself—that was limiting certain aspects of athletic performance.

Carnivore, paleo, and ketogenic diets: What’s the difference?

It’s easy to confuse the carnivore diet with paleo or ketogenic diets. Although they may appear to share certain similarities, they differ in some key aspects:

• Paleo: Includes animal and plant foods and excludes grains and legumes
• Ketogenic: Includes animal and plant foods while restricting carbohydrates. Most grains and legumes are excluded, but can include some low-carb plant foods and dairy
• Carnivore: Strictly animal foods—no plants at all

Understanding the differences is essential for anyone studying nutrition or personal training, as dietary advice must be tailored to the individual.

Why this matters for future PTs and nutritionists

Trends like the carnivore diet are a perfect example of why evidence-based practice matters. As a future personal trainer or nutrition professional, you’ll need to:

• Analyse diet trends critically
• Identify potential nutrient gaps
• Tailor programs safely for clients
• Base recommendations on science, not hype

Our courses teach all of this—giving you the skills to evaluate diets, design effective nutrition plans, and help clients achieve real results.

Bottom line

Science appears to support the health benefits of the carnivore diet proposed by its advocates. On the other hand, it also validates the concerns raised by its critics, such as the potential health implications resulting from a lack of certain micronutrients.

Before making any judgements, it’s important to understand that, to date, the carnivore diet has been the subject of very few peer-reviewed studies. It may indeed provide some beneficial effects with certain modifications. However, a recurring theme in the existing literature is the need for greater investigation before any definitive advice can be given regarding its safety and efficacy.

For prospective students, understanding diets like this demonstrates the critical thinking and evidence-based skills you’ll need to develop in your PT or nutrition studies.

Thinking about a career in fitness or nutrition? Our courses prepare you to guide clients safely, separate fact from hype, and make informed, professional decisions.

References

1) Little JF. A six weeks’ experiment with the Salisbury diet. Br Med J. 1886;2(1339):685 6.

2) Goedeke S, Murphy T, Rush A, Zinn C. Assessing the Nutrient Composition of a Carnivore Diet: A Case Study Model. Nutrients. 2024 Dec 31;17(1):140. doi: 10.3390/nu17010140. PMID: 39796574; PMCID: PMC11722875.

3) Lennerz BS, Mey JT, Henn OH, Ludwig DS. Behavioral Characteristics and Self-Reported Health Status among 2029 Adults Consuming a “Carnivore Diet”. Curr Dev Nutr. 2021 Nov 2;5(12):nzab133. doi: 10.1093/cdn/nzab133. PMID: 34934897; PMCID: PMC8684475.

4) Norwitz NG, Soto-Mota A. Case report: Carnivore-ketogenic diet for the treatment of inflammatory bowel disease: a case series of 10 patients. Front Nutr. 2024 Sep 2;11:1467475. doi: 10.3389/fnut.2024.1467475. PMID: 39296504; PMCID: PMC11409203.

5) Sources: Bowser SM, Cloutier E, Romano V. Carnivore diet and athletic performance: a case study analysis. J Exerc Nutr. 2024;7(1):10.

Author

Paul Orridge

Paul Orridge BSc (Hons)

Paul Orridge is a graduate in the field of sport, exercise and health, and has over 30 years’ experience within the fitness industry. In this time, he has performed a variety of roles including personal training, lecturing and writing. Paul now works as a freelance technical author and subject matter expert within the fitness industry. His work is based on his practical experience gained working with a diverse range of people from very unfit, overweight individuals to highly conditioned athletes, and is underpinned by the latest research.