How My VO2 Max Changed on Meat-Only
Tracking Cardio Fitness on a Carnivore Diet
Switching to a meat-only diet brought noticeable changes in VO2 max, one of the most important indicators of cardiovascular fitness and aerobic capacity. After adopting a strictly meat-based diet, their VO2 max shifted, offering clear insight into how nutrition choices can directly affect fitness measurements. This experience provides a unique perspective on the relationship between diet and measurable physical performance.
VO2 max is often influenced by both genetic factors and lifestyle choices such as exercise and nutrition. Since the body’s ability to use oxygen efficiently relies on the health of the heart, lungs, and muscles—and since nutrients from food support these systems—a major dietary shift can affect VO2 max results over time.
For anyone tracking their own fitness or considering dietary changes, understanding how a meat-only approach influences VO2 max may offer valuable guidance. This account explores those changes, supported by both personal data and current research.
Understanding VO2 Max
VO2 max is a primary indicator of cardiovascular fitness and reflects how efficiently the body can use oxygen during intense activity. It is often used to gauge aerobic fitness, measure progress, and compare fitness levels across different individuals.
What Is VO2 Max
VO2 max, or maximal oxygen uptake, measures the maximum amount of oxygen an individual can utilize per minute, per kilogram of body weight, while performing intense exercise. The value is typically expressed as milliliters of oxygen per kilogram per minute (ml/kg/min). It represents a person's peak capacity to transport and use oxygen during exercise.
This measurement is considered useful for understanding an athlete’s aerobic power. However, it's not the sole predictor of performance or fitness level. Other factors, such as running economy and lactate threshold, also affect endurance and overall capability. Still, VO2 max remains a standard benchmark for evaluating cardiovascular fitness in sports science.
Table: Typical VO2 Max Ranges
Category Male (ml/kg/min) Female (ml/kg/min) Sedentary Adults 30-40 27-30 Active Adults 40-50 31-41 Trained Athletes 55-70 46-60
How VO2 Max Is Measured
VO2 max is most accurately measured in a controlled laboratory setting using a graded exercise test. The subject exercises on a treadmill or stationary bike while connected to equipment that analyzes respiratory gases. The workload is incrementally increased until exhaustion, capturing the highest rate of oxygen usage.
Wearable devices and fitness watches estimate VO2 max based on heart rate, pace, and user-provided data. These methods use algorithms and provide a general approximation. While not as precise as lab tests, these estimates are convenient for tracking trends in cardiovascular fitness over time.
Several factors can influence measured values. These include age, sex, genetics, training status, altitude, and even body weight. For accuracy, consistent testing protocols and conditions are important.
VO2 Max and Overall Fitness
VO2 max is closely tied to aerobic fitness because it reflects an individual's ability to deliver and utilize oxygen during physical activity. Higher VO2 max values generally indicate superior cardiovascular fitness and a greater capacity for sustained exercise. Trained athletes often have higher VO2 max levels than sedentary individuals.
Despite its relevance, VO2 max does not capture all aspects of fitness. Performance in endurance sports also depends on movement efficiency, muscular endurance, and threshold speeds. For most people, improvements in VO2 max usually translate to noticeable gains in aerobic capacity and general physical conditioning.
Physicians and coaches may use VO2 max to assess cardiovascular health and monitor the effects of training or lifestyle changes. For individuals tracking their own progress, significant shifts in VO2 max can signal changes in fitness level, adaptation to training, or possible effects of dietary habits.
The Meat-Only Diet: Overview and Rationale
A meat-only diet centers exclusively on animal-based foods such as beef, pork, and fish. Supporters often cite physical performance, weight management, and simplified nutrition as key motivations for adopting this approach.
Principles of a Meat-Only Diet
The core principle of a meat-only diet is the exclusion of all plant foods, focusing only on foods such as red meat, poultry, fish, eggs, and sometimes dairy. Processed meats and organ meats may also be included.
This diet is usually very high in protein and fat, while containing virtually no carbohydrates or dietary fiber. Proponents argue that this mimics the nutritional patterns of ancient hunter-gatherer diets.
Preparation methods typically avoid breading, sugars, and sauces that contain plant ingredients. Meals become predictable, which may simplify caloric intake tracking for some individuals.
Nutritional Profile of Red Meat
Red meat is a primary source of essential nutrients on a meat-only diet. It is packed with complete protein, providing all nine essential amino acids. Red meat also supplies iron, zinc, selenium, and vitamin B12 in highly bioavailable forms.
The diet’s fat content comes primarily from saturated and monounsaturated fats, which contribute to energy needs. Some cuts, such as ribeye or ground beef, are especially high in saturated fat.
Cholesterol levels in red meat are relatively high compared to white meat or fish. However, cholesterol intake does not always have a clear impact on blood cholesterol for every individual, as the response varies based on genetics and other factors.
Potential Health Benefits and Risks
Some people notice short-term benefits, such as weight loss and improved satiety, possibly due to stable blood sugar and reduced caloric intake. Others have reported improvements in symptoms of autoimmune or digestive disorders, though these outcomes lack large-scale scientific validation.
Potential risks of a meat-only diet include nutrient deficiencies (such as vitamin C, fiber, and phytonutrients found in plants), increased intake of saturated fat and cholesterol, and changes in gut microbiota due to the absence of fiber. There is also concern about possible increases in cardiovascular risk factors, especially for those predisposed.
Fish, as part of a meat-only diet, may provide beneficial omega-3 fatty acids, which can help balance saturated fat intake. Still, medical guidance is recommended before starting this or any restrictive diet.
My VO2 Max Data Before and After the Meat-Only Diet
The effects of a meat-only diet on aerobic capacity can be evaluated by examining VO2 max values, changes in body composition, and related cardiovascular measures. Comparing VO2 max data before and after dietary intervention gives insight into how muscle mass, weight loss, and fat percentage may shift with nutritional changes.
Baseline Testing and Measurements
Before starting the meat-only diet, VO2 max was tested using a treadmill protocol with respiratory gas analysis. The participant's VO2 max measured 34 mL/kg/min. Body composition was assessed with a DEXA scan, showing a body fat percentage of 23%, a weight of 74 kg, and a lean muscle mass estimate of 54 kg.
The baseline heart rate at rest was 64 bpm, and average exercise heart rate during submaximal effort was 135 bpm. These measurements established the initial fitness status and provided reference points for all subsequent tracking. No significant illness or medication use affected the initial results. All data was collected in the morning after an overnight fast to reduce day-to-day variation.
Protocol for Tracking Changes
The tracking protocol included monthly VO2 max tests, performed under similar time-of-day and fasting conditions. Each test replicated the original methodology, using identical equipment and intensity progression. Body composition was re-evaluated every two months with DEXA to monitor shifts in body fat and muscle mass.
To improve reliability, daily resting heart rate and weight were also logged. The participant maintained the meat-only diet strictly, with all meals recorded. Any changes in exercise routines or lifestyle were noted in a digital log. All results were processed in a spreadsheet, and key metrics were regularly summarized in the following table:
Date VO2 max (mL/kg/min) Weight (kg) Body Fat (%) Muscle Mass (kg) Baseline 34 74 23 54 Month 1 36 72 21 54.5 Month 2 37 71.5 20 55
Impact of Meat-Only Diet on Cardiovascular Fitness
A meat-only diet can produce changes in cardiovascular fitness, especially regarding aerobic capacity and endurance. While some experience changes in VO2 max, shifts in workout performance and training adaptation also become apparent.
Aerobic Capacity Alterations
VO2 max, the maximal amount of oxygen that the body can use during intense exercise, is a core metric for aerobic fitness. Some individuals on meat-only diets report initial stability or even increases in VO2 max, possibly due to weight loss or reduced inflammation. Weight loss, in particular, is a known factor that can improve aerobic output.
However, there are potential drawbacks. The lack of carbohydrates in a carnivorous diet can lead to decreased glycogen stores, which may limit the ability to sustain high-intensity aerobic efforts over time. This could result in slower recovery after demanding workouts.
The balance of micronutrients, such as potassium and magnesium, also shifts with a meat-only regimen. These nutrients are essential for optimal cardiovascular and muscle function during aerobic exercise. Deficiencies could subtly reduce aerobic capacity or workout quality.
Endurance and Performance Results
Endurance and sustained training performance are influenced by diet composition. On a meat-only diet, some report early short-term increases in endurance, possibly from weight loss or steady energy from fats and protein. This can help with longer, low-intensity sessions which rely less on glycogen.
Yet, a notable challenge emerges during repeated or high-intensity endurance workouts. The reduced carbohydrate intake limits quick-access energy, leading to early fatigue or difficulty maintaining pace, especially in interval training or competitions.
Users of meat-only diets can experience changes in subjective energy levels during extended training cycles. Some find their energy predictable, while others notice a drop in peak performance or slower progress in their cardiovascular training, as seen by plateauing or dips in time trial results and training logs.
Energy and Workout Adaptations
On a meat-only diet, the body's preferred energy sources shift, especially during exercise. This can influence how workouts feel, how muscles perform, and how recovery and adaptation take place.
Fuel Utilization on a Zero-Carb Diet
A zero-carb diet, such as carnivore, eliminates most or all dietary carbohydrates. This leads to reduced muscle glycogen stores compared to mixed or high-carbohydrate diets, as glycogen is primarily replenished through carbohydrate intake.
The body adapts by increasing reliance on fat oxidation for energy both at rest and during endurance exercise. As a result, some people report steady energy during extended activities but reduced ability to perform high-intensity, explosive efforts that depend on anaerobic glycolysis and immediate carbohydrate availability.
Effects may include:
Lower muscle glycogen levels
Higher rates of fat metabolism
Possible initial decrease in exercise intensity for sprints or intervals
More stable energy for long, steady-state workouts
Athletes following this diet may find their endurance is maintained or only slightly reduced, but they often see a drop in peak power output if carbohydrate intake is not reintroduced before short, high-intensity efforts.
Effects on Strength and Resistance Training
Strength and resistance training on a meat-only diet present specific considerations. Glycogen fuels short, intense muscle contractions, so limited carbohydrate intake may reduce glycogen stores and potentially affect maximal lifts or high-volume sessions.
Some research suggests that diets low in carbohydrates can be associated with a modest reduction in anaerobic performance, especially when multiple sets or sprints are performed. This is because glycogen is the main substrate for high-intensity resistance work.
Yet, protein intake is naturally high on a meat-only diet, which supports muscle repair and growth. Many report maintained or even improved recovery between sessions, likely due to elevated dietary protein and fat.
However, some individuals feel increased fatigue and find it harder to progress in strength-based workouts if glycogen stores are chronically low.
In summary, adaptations are highly individual. A person may notice slight reductions in anaerobic strength or volume performance on a zero-carb approach, while experiencing steady progress in muscle maintenance and recovery.
Health Markers and Body Composition Shifts
Key health metrics, including cholesterol, blood glucose, body fat percentage, and muscle mass, show measurable changes on a meat-only diet. Individual responses may differ, but certain trends are seen in existing studies and case reports.
Changes in Cholesterol and Blood Glucose
After switching to a meat-only diet, the individual's cholesterol levels showed both expected and unexpected shifts. Total cholesterol and LDL cholesterol often increased, sometimes significantly. HDL cholesterol remained stable or increased slightly in some cases. Triglycerides generally decreased, especially when carbohydrates were nearly eliminated.
Blood glucose values revealed more stability throughout the day. Fasting blood glucose sometimes dropped slightly, and post-meal spikes were less common compared to a carbohydrate-inclusive diet. This aligns with research showing lower glycemic fluctuations when carbohydrates are minimized. However, some people reported slight elevations in fasting glucose, though these did not always indicate impaired metabolic health.
Body Fat and Muscle Mass Trends
Body composition changed in several ways while following a meat-only diet. Body fat percentage often decreased, which was supported by regular tracking through scales or skinfold calipers. This shift was more pronounced in those who maintained a consistent calorie deficit and combined the diet with regular exercise.
Muscle mass was often maintained or increased, provided protein intake stayed adequate. Meat-based diets are naturally high in protein, supporting the retention of lean tissue. Some studies noted a trend toward modest muscle gain when training intensity was kept high and recovery was sufficient. Water weight tended to normalize after the initial weeks, which sometimes confounded early measurements.
Lifestyle Modifications During the Experiment
Routine changes during the study influenced several daily habits. These included sleep patterns, recovery strategies, stress reduction methods, and the types of physical activity performed.
Sleep and Recovery Habits
The participant set a strict bedtime between 10:00 and 10:30 pm, aiming for at least 7.5 hours of sleep per night. The goal was consistent rest rather than fluctuating sleep schedules.
They used a sleep tracker to monitor quality, focusing on time spent in deep and REM phases. Naps were allowed after intense gym workouts or adventure sports days.
For recovery, they followed a cooldown routine with static stretching after exercise, and used a massage gun when muscle soreness occurred. Hydration was emphasized, especially after climbing and prolonged gym sessions.
Sleep Tracking:
Aspect Method Outcome Duration Device/App Avg. 7.7 hours/night Deep Sleep Device Monitored for progress Night Routine Phone off Early Improved consistency
Meditation and Stress Management
A daily meditation practice was adopted, lasting 10 minutes each morning before breakfast. The focus was on guided breathing and mindfulness.
Journaling was added three days per week to process stressors and track progress. They noted subjective stress levels on a scale from 1–5, adjusting routines if marked increases occurred.
Light stretching and controlled breathwork were performed after evening meals to assist in winding down. When anxiety increased before competitions or long adventure climbs, extra meditation sessions were scheduled.
Key Stress Management Practices:
10-min daily meditation
Three weekly journaling entries
Evening breathwork sessions
Physical Activity and Adventure Sports
Exercise continued 5–6 days per week, consisting of strength training in the gym, regular indoor climbing, and weekend adventure sports. Workouts were tracked for intensity and duration, targeting improvements in endurance and power.
Climbing sessions focused on both bouldering and sport climbing, with routes increasing in difficulty over the course of the diet. Cardio sessions were done twice weekly, each lasting 30–40 minutes at moderate intensity, typically on a treadmill using an incline protocol similar to the Bruce protocol.
Adventure activities, such as trail running or outdoor climbing trips, occurred at least twice per month. Each session was logged for duration, elevation gained, and recovery needs. A balance between high-intensity effort and sufficient rest was prioritized to minimize overtraining.
Comparisons to Other Dietary Approaches
Different dietary patterns influence VO2 max by altering macronutrient balance, impacting aerobic performance and metabolic response. Attention to carbohydrate quality and nutritional variety can significantly affect endurance, especially when compared to strict meat-only regimens.
Carbohydrate-Based Diets vs Meat-Only
Carbohydrate-based diets emphasize grains, fruits, and starchy vegetables, providing the primary source of energy for sustained aerobic exercise. Glycogen repletion is faster with high-carbohydrate intake, supporting endurance and enabling longer training sessions at higher intensities.
In contrast, a meat-only approach eliminates nearly all dietary carbohydrates. This causes a reliance on fat and protein for fuel. Evidence suggests that this may lower glycogen stores, potentially limiting VO2 max improvements during intense aerobic activity. Athletes on meat-only diets sometimes notice a reduction in time to exhaustion compared to those consuming plenty of carbs.
Key differences include:
Diet Type Main Fuel Source Impact on VO2 Max Carbohydrate Carbs (glycogen) Supports higher VO2 max Meat-Only Fat/protein May limit VO2 max gains
Effects of Sweet Potatoes and Fish Inclusion
Inclusion of sweet potatoes in the diet provides a dense, nutrient-rich source of carbohydrates. This improves muscle glycogen levels, helping the body sustain elevated VO2 max during prolonged activities. The natural vitamins and minerals in sweet potatoes also support cardiovascular health.
Adding fish offers lean protein and omega-3 fatty acids. These nutrients may enhance recovery and reduce inflammation, adding metabolic benefits without excessive saturated fat intake. Fish consumption, compared to only red meat, may provide advantages in heart function and blood vessel flexibility, which can positively influence VO2 max outcomes.
In summary, integrating sweet potatoes and fish supplies key macronutrients and micronutrients that a strict meat-only diet lacks, potentially maximizing VO2 max improvements while supporting holistic nutrition.
Long-Term Implications and Observations
Long-term changes in VO2 max from a meat-only diet may affect both how the body ages and risk factors for major diseases. These effects can vary based on individual health, baseline fitness, and dietary adherence.
Potential Impact on Longevity and Disease Risk
VO2 max is one of the clearest indicators of cardiorespiratory fitness and is strongly correlated with life expectancy. Studies show that higher VO2 max values are linked with lower all-cause mortality, including reduced risks of cancer and dementia.
A meat-only diet may influence body composition and metabolic markers that affect VO2 max. While increased protein intake can help preserve lean muscle, the lack of plant-based nutrients such as fiber and antioxidants might have implications for long-term health outcomes.
Reduced intake of carbohydrates may affect energy levels during sustained aerobic exercise, sometimes leading to decreased performance or VO2 max over time. This could, in turn, blunt some of the positive longevity benefits typically seen with higher VO2 max values.
Dietary patterns and VO2 max together influence disease risk. Adherence to a meat-only approach could alter markers like fasting glucose and insulin sensitivity, which are important for diabetes risk.
Heart Health and Disease Considerations
Cardiorespiratory fitness, as reflected by VO2 max, is a strong independent predictor of heart health. A higher VO2 max is generally associated with lower heart disease risk and better vascular function.
A meat-only diet emphasizes saturated animal fats and cholesterol. This dietary choice may influence LDL cholesterol and other heart disease biomarkers. For some, these changes could raise cardiovascular risk despite unchanged or even improved VO2 max.
On the other hand, increased protein and reduced processed food intake can have positive effects on blood pressure and triglycerides. The absence of dietary fiber, however, is relevant. Fiber intake is associated with lower rates of heart disease, and a lack thereof may negate potential benefits from exercise-induced VO2 max improvements.
Key risk factors affected include:
Risk Factor Meat-Only Diet Effect VO2 Max Relationship LDL Cholesterol May increase Higher VO2 max may offset some risk Blood Pressure May decrease or stay stable Improved with higher fitness Insulin Sensitivity Variable Better with higher VO2 max
Key Takeaways and Reflections
The data showed a modest change in VO2 max values after switching to a meat-only diet. While the participant remained within a normal cardiorespiratory fitness range, no dramatic increase or sharp decline was observed.
Muscle Utilization Matters:
Performance was influenced not just by oxygen delivery to the muscles, but also by how those muscles could use the available oxygen. Diet may play a role in muscle efficiency, but training remains a major factor.
Hydration and electrolyte management became even more important on a meat-only regimen. Adjusting salt and water intake helped offset potential changes in blood volume and energy during testing and training.
Aspect Pre-Transition Post Meat-Only Notable Change VO2 Max (ml/kg/min) 41 40.5 Slight decrease Resting Heart Rate 62 61 Slight improvement Recovery Time Normal Normal No significant shift
A focus on high-intensity intervals and steady-state training sessions was key for maintaining aerobic capacity. The inclusion of strength training helped preserve muscle function, further supporting cardiorespiratory performance.
Diet composition alone did not appear to cause major shifts in VO2 max within the measured period. Fitness and adaptations depended more heavily on sustained and varied exercise
