Health Transformation: 28-Day Vegan vs. Carnivore Diet Swap Reveals Surprising Results (2025 Study)
In April 2025, an intriguing 28-day diet swap experiment revealed compelling insights into how different dietary choices impact human health. Two individuals with opposing food philosophies—Chase, a 10-year vegan, and Joe, a dedicated carnivore—switched diets completely for four weeks while monitoring various health markers. Both participants underwent comprehensive blood testing before and after the experiment to quantify the physiological effects of their temporary dietary transitions.
The results painted a nuanced picture of how quickly the body responds to dietary changes. Joe experienced difficulty adapting to the plant-based regimen, struggling with energy levels while consuming primarily fruits and rice-based meals. Meanwhile, Chase reported significant fatigue and reduced mental clarity on the carnivore diet, noting that it took his body much longer to convert animal fats into usable energy compared to his usual carbohydrate-rich vegan diet. Blood work analyses showed particularly notable changes in inflammation markers, cholesterol levels, and IGF-1—with the plant-based diet generally demonstrating more favorable outcomes across these important health indicators.
Key Takeaways
Blood tests revealed the plant-based diet reduced inflammation markers and cholesterol levels more effectively than the carnivore diet.
Both participants experienced energy and cognitive challenges when adapting to unfamiliar dietary patterns during the 28-day experiment.
Regardless of dietary choice, the results suggest supplementation of vitamin B12 and vitamin D may be beneficial for optimal health.
Participant Profiles
Chase's Plant-Based Journey
Chase embraced veganism ten years ago, motivated by environmental concerns and health benefits. His long-term commitment to a plant-based lifestyle established his baseline health markers before the experiment began. During the 28-day carnivore challenge, Chase struggled significantly with energy levels. About two weeks into the experiment, he nearly quit as his body attempted to adapt to using animal fat as its primary fuel source.
The transition away from carbohydrates proved particularly difficult for Chase. He reported that meals took approximately 45 minutes before he felt enough energy to resume activities, and he experienced persistent fatigue throughout the month. His cognitive function also seemed affected, with Chase noting that his "brain wasn't moving as quickly" as he desired.
Despite these challenges, the experiment ultimately reaffirmed Chase's commitment to veganism. The experience "reignited" his original values and provided perspective on modern processed vegan foods, reminding him of the importance of making thoughtful food choices even within a plant-based framework.
Joe's Meat-Based Approach
Joe entered the experiment as a dedicated carnivore who worked in construction. His regular diet consisted primarily of animal products, with fat and protein serving as his main energy sources. When switching to a vegan diet for 28 days, Joe adopted a sparse eating pattern that likely contributed to his difficulties.
His daily food intake included:
Morning: Coffee with coconut oil
Lunch: Primarily fruits (typically apples with nut butter)
Dinner: Plant proteins with carbohydrates (beans, rice, sweet potatoes, stir-fries)
This limited meal structure—consuming only two proper meals daily with one being mostly fruit—created challenges for Joe's satisfaction and energy levels. The insufficient caloric intake and food variety likely impacted his experience negatively.
Despite the blood work showing significant health improvements during his plant-based month, including dramatic reductions in inflammation markers, cholesterol levels, and stress hormones, Joe returned to his carnivore diet after completing the experiment. His body demonstrated positive responses to plant foods even while he personally found the diet challenging.
Diet Experiment: Plant vs Animal-Based Eating
Joe's Vegan Journey
Joe, a construction worker who normally follows a carnivore diet, switched to a plant-based regimen for 28 days as part of a controlled experiment. His typical daily intake consisted of only two meals - morning coffee with coconut oil, followed by fruits with nut butter for lunch. Dinner usually featured beans, rice, sweet potatoes, or vegetable stir-fries.
The limited meal frequency and composition likely contributed to Joe feeling unsatisfied during the experiment. Despite his personal discomfort with the dietary change, his body showed remarkable improvements in several biomarkers.
Joe's health metrics improved significantly on the plant-based diet. His insulin levels decreased, and his cortisol (stress hormone) levels dropped dramatically. His IGF-1 levels, which are linked to cancer risk, also decreased - a positive change from a health perspective.
Chase's Carnivore Experience
Chase, who had maintained a vegan lifestyle for ten years due to environmental and health concerns, struggled considerably when switching to the carnivore diet. About two weeks into the experiment, he nearly quit due to persistent energy issues.
The carnivore diet forced Chase's body to rely primarily on saturated animal fat for energy instead of carbohydrates. This metabolic shift likely contributed to his reported fatigue and mental fog. He specifically noted that meals took approximately 45 minutes before he felt energized enough to continue with activities.
Chase's blood work revealed several concerning changes. His insulin and overall cholesterol levels increased, including a rise in LDL ("bad" cholesterol). His IGF-1 levels also increased - a biomarker associated with higher cancer risk when elevated.
Key Blood Test Results Comparison:
Biomarker Joe (Vegan Diet Effect) Chase (Carnivore Diet Effect) Vitamin B12 Minimal change Slight increase Vitamin D Below normal (both before/after) Below normal (both before/after) Insulin Decreased Increased Cortisol Dramatically reduced Remained stable IGF-1 Decreased Increased C-reactive protein Decreased from above normal Slight decrease from healthy baseline LDL Cholesterol Reduced to healthy levels Increased
Both participants showed below-normal vitamin D levels regardless of diet, suggesting supplementation might be beneficial for either dietary approach.
Impact on Energy and Digestion
The diet swap experiment revealed significant differences in how the body processes plant versus animal foods. Chase experienced noticeable energy issues during his carnivore diet phase. His body struggled to adapt to using fat as the primary energy source instead of carbohydrates.
After meals, Chase reported needing approximately 45 minutes before feeling energized enough to resume activities. This delay contrasts with the quicker energy release typically experienced with carbohydrate consumption. His cognitive function also seemed affected, with Chase mentioning his brain wasn't "moving as quickly" as desired.
Joe's vegan diet implementation created its own challenges. His daily food intake consisted of just two meals - primarily fruit with nut butter for lunch and bean/rice combinations for dinner. This restricted eating pattern likely contributed to feelings of dissatisfaction, as both meal frequency and caloric density were insufficient.
The blood work results provided concrete evidence of physiological changes. Insulin levels showed an interesting pattern - Chase's increased on the carnivore diet while Joe's decreased on the plant-based diet. Cortisol levels, which indicate bodily stress, remained stable for Chase but dropped dramatically for Joe, suggesting his body responded positively to plant foods despite his personal preferences.
Digestive health markers also revealed telling patterns. C-reactive protein, an inflammation indicator, showed minimal change for Chase from his already healthy baseline. Joe's levels, however, plummeted from concerning elevations to healthier ranges after adopting a plant-based diet.
Cholesterol measurements further illustrated dietary impacts on digestion and metabolism. Chase's LDL (often called "bad" cholesterol) increased considerably during his carnivore experiment. Conversely, Joe's previously elevated cholesterol levels reduced to normal ranges on the plant-based diet.
Despite the clear physiological benefits Joe experienced, he chose to return to his carnivore eating habits after the experiment concluded. Chase, meanwhile, reported the experiment had "reignited" his commitment to plant-based eating, though he noted the importance of avoiding processed vegan foods.
Blood Test Results
Vitamin Measurements
The experiment revealed interesting patterns in vitamin levels for both participants. Vitamin D remained below normal ranges for both individuals before and after the diet swap, suggesting this nutrient is challenging to obtain regardless of dietary approach. This indicates that supplementation may be beneficial for people following either eating pattern, particularly in regions with limited sunlight exposure.
Vitamin B12 showed a similar trend. The participant on the carnivore diet experienced a slight increase in B12 levels, likely due to consuming animal products that contained recycled B12 supplements given to farmed animals. These findings suggest that vitamin supplementation might be worthwhile consideration for both dietary approaches.
Hormone Level Shifts
The insulin measurements showed notable changes during the experiment. The participant following the carnivore diet experienced increased insulin levels, while the participant on the plant-based diet saw his insulin levels decrease, which represents a positive health outcome.
Cortisol measurements, which indicate bodily stress levels, revealed that the carnivore dieter maintained relatively stable cortisol throughout the experiment. Interestingly, the plant-based dieter experienced a significant reduction in cortisol levels, suggesting his body responded positively to the plant-based approach despite his personal dissatisfaction with the diet itself.
Growth Factor and Cancer Indicators
IGF-1 (Insulin-like Growth Factor 1) levels showed significant variation between the two dietary approaches. This biomarker holds particular importance as elevated levels have been linked to increased cancer risk in scientific research.
Dieter Diet IGF-1 Change Chase Carnivore Increased Joe Plant-based Decreased
The participant who switched to the carnivore diet showed increased IGF-1 levels, while the participant on the plant-based diet experienced a decrease in IGF-1, suggesting potential cancer risk reduction benefits associated with plant-based eating.
Inflammatory Response Measurements
C-reactive protein (CRP), which measures inflammation in the body, showed revealing differences between the participants. The carnivore dieter's CRP levels decreased slightly from an already healthy baseline.
More dramatically, the plant-based dieter began with CRP levels well above the safe range during his carnivore phase, but these levels dropped substantially after adopting the plant-based diet. This significant reduction suggests the plant-based approach may offer anti-inflammatory benefits for some individuals.
Blood Lipid Profiles
The cholesterol measurements provided compelling insight into how quickly dietary changes can affect cardiovascular health markers. The participant who switched to the carnivore diet experienced increases in both overall cholesterol and LDL ("bad") cholesterol levels during the 28-day period.
Conversely, the participant who adopted the plant-based diet saw his cholesterol levels decrease from previously elevated readings to within healthy ranges. This rapid improvement in lipid profiles aligns with research suggesting plant-based diets may support better cardiovascular health outcomes.
Post-Experiment Reflections
Joe's Return to Carnivore Diet
Despite the compelling blood test results showing significant health improvements, Joe decided to return to his carnivore diet after completing the 28-day experiment. His vegan diet during the trial consisted mainly of fruits with nut butter for lunch and beans with rice for dinner, with only two meals per day. This limited eating pattern likely contributed to his dissatisfaction with the plant-based approach.
The blood tests revealed several positive changes for Joe while on the vegan diet. His insulin levels decreased, suggesting improved metabolic health. Perhaps most notably, his cortisol levels (a stress hormone) dropped dramatically, indicating his body responded well to plant foods despite his personal dislike of the diet.
Joe's inflammatory markers, measured by C-reactive protein, fell from well above the safe range to much healthier levels during his plant-based experiment. Similarly, his cholesterol readings, which had been significantly elevated during his carnivore phase, decreased to normal ranges on the vegan diet. His IGF-1 levels (associated with cancer risk) also decreased when consuming only plants.
Chase's Reaffirmed Vegan Values
After ten years as a vegan, Chase's experience with the carnivore diet reinforced his commitment to plant-based eating. During the experiment, he struggled significantly with the meat-heavy regimen, reporting persistent fatigue and mental fog. By the two-week mark, Chase nearly abandoned the experiment due to low energy levels and the slow digestion process—noting it took about 45 minutes after meals before he felt able to function.
The blood test results validated several of Chase's concerns. His insulin and cholesterol levels increased on the carnivore diet, with both overall and LDL ("bad") cholesterol showing concerning elevations. His IGF-1 levels also rose, which scientific studies have linked to increased cancer risk.
"Through the experiment, I wanted to find out for myself if there's any truth to the keto carnivore trend," Chase explained. "It actually reignited some of the values I had previously—especially now that veganism has gone mainstream with all the processed foods, you still have to be smart about what you're eating."
The experience served as a scientific confirmation of Chase's ethical and health choices, strengthening his resolve to maintain his plant-based lifestyle while being mindful of food quality.
Conclusion and Credibility
The experiment comparing carnivore and vegan diets over 28 days revealed noteworthy changes in both participants' biomarkers. Blood tests demonstrated significant shifts in several key health indicators during this dietary swap. Though each participant struggled with their temporary diet change, the physical evidence told a compelling story.
It's important to acknowledge the limitations of this experiment. This was not a peer-reviewed study but rather an informal experiment between two individuals without medical supervision. The experiment was organized by a carnivore vlogger named Drew Morg and hosted on his channel, potentially introducing bias toward meat-based diets.
The biomarker results showed several interesting patterns:
Biomarker Carnivore Diet Effect Vegan Diet Effect Vitamin B12 Marginal increase No significant change Vitamin D Below normal (both) Below normal (both) Insulin Increased Decreased Cortisol Remained stable Decreased dramatically IGF-1 (cancer risk) Increased Decreased C-reactive protein Decreased slightly Dropped significantly Cholesterol Increased overall Reduced to healthy levels
Both diets showed deficiencies in essential nutrients like vitamin D and B12, suggesting supplementation might be necessary regardless of dietary choice. The vegan diet demonstrated advantages in reducing inflammation, stress hormones, and cancer risk factors. Despite the favorable health outcomes for the temporary vegan participant, he chose to return to his carnivore diet after the experiment ended.
The carnivore-turned-vegan participant found the experiment reaffirmed his original values about plant-based eating. He noted that even within veganism, food choices matter - particularly with the rise of processed vegan options in mainstream markets.
