Once you hit 40, your body isn’t playing by the same rules it did in your 20s and 30s. Muscle mass starts to decline (around 3–8% per decade), testosterone levels begin to drop, and fat storage becomes more stubborn. That’s why your diet isn’t just about looking good anymore—it’s about maintaining strength, boosting recovery, and supporting hormonal balance to stay competitive in the gym and in life.
The right diet can make or break your progress. Get it wrong, and you’ll struggle to gain muscle, recover slowly, and feel drained all the time. Get it right, and you’ll not only look stronger but feel sharper, more energized, and healthier overall. That’s why choosing the best diet isn’t just about personal preference—it’s about finding a strategy that supports your body’s changing needs.
Table of Contents
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What This Article Will Cover
This article is going to cut through the noise and give you an objective comparison of four of the most popular diets: Carnivore, Vegan, Keto, and Traditional Omnivorous. We’ll evaluate each one based on its:
- Muscle-building potential
- Fat-burning capability
- Effect on energy and recovery
- Long-term health impact
No fluff, no fads—just a straight-up analysis based on science and real-world effectiveness. The goal here isn’t to promote any particular diet (okay, maybe a little) but to give you the facts so you can make an informed decision based on what actually works for men over 40.
Why You Should Listen to This Advice
Most diet advice out there is either overly complicated, based on short-term results, or rooted in ideology rather than science. This isn’t that. We’re looking at peer-reviewed research, real-world results, and the unique needs of men over 40 who want to build muscle, stay lean, and keep their testosterone levels optimized.
No matter where you’re starting from—or which diet you’re currently following—you’ll walk away from this article with a clear understanding of which approach gives you the best shot at maximizing muscle growth, burning fat, and staying strong well into your 50s and beyond. Let’s get into it.
Carnivore Diet
Origin & History
The Carnivore Diet taps into the idea that early humans were primarily meat-eaters. Proponents argue that our ancestors thrived on hunting large animals and consuming a diet made up almost entirely of animal-based foods—meat, organs, fat, and bone marrow. While historical evidence suggests that early humans were more likely opportunistic omnivores (consuming plants and animal products depending on availability), the Carnivore Diet claims that a meat-heavy approach aligns more closely with our evolutionary roots.
The modern revival of the Carnivore Diet can be traced back to Dr. Shawn Baker, an orthopedic surgeon and former athlete who became the face of the movement after publishing "The Carnivore Diet" in 2019. Baker argued that eliminating plant-based foods could resolve inflammation, improve digestion, and enhance athletic performance. He promoted the idea that plants contain anti-nutrients (like oxalates and lectins) that can interfere with nutrient absorption and cause gut issues.
Baker’s influence quickly spread through the fitness and biohacking communities, fueled by anecdotal reports of improved strength, fat loss, mental clarity, and reduced inflammation. High-profile figures like Joe Rogan and Jordan Peterson publicly experimented with the diet, further amplifying its reach. The rise of the “Carnivore Tribe” on social media created a loyal following among athletes and bodybuilders looking to simplify their diets and maximize performance.
What the Carnivore Diet Involves
The Carnivore Diet is straightforward: eat only animal-based foods. That includes:
- Meat – Beef, lamb, pork, poultry, game
- Fish and seafood – Salmon, sardines, mackerel, shellfish
- Animal fats – Butter, tallow, lard
- Eggs
- Organ meats – Liver, heart, kidney
No fruits, vegetables, grains, legumes, nuts, or processed foods. The strictest versions even eliminate dairy and seasoning (other than salt).
What Carnivore Is Best For
- Rapid fat loss – The lack of carbs puts the body into a ketogenic state, encouraging fat burning.
- Muscle preservation – High protein intake supports muscle maintenance and growth.
- Simplicity – No meal planning or calorie counting; just eat meat.
- Autoimmune and gut issues – Some people report improved digestion and reduced inflammation after eliminating plant-based foods.
Pros
✔️ High protein content – Supports muscle growth and recovery.
✔️ Fat-adapted metabolism – Encourages fat burning and stable energy levels.
✔️ Eliminates processed food – No room for junk food means reduced cravings and better satiety.
✔️ Easy to follow – No complicated meal plans or macro tracking.
Cons
❌ Nutrient deficiencies – Lack of plant-based foods means potential shortages in fiber, vitamin C, potassium, and magnesium.
❌ Digestive issues – High-fat, low-fiber diets can cause constipation for some people.
❌ Sustainability – Social and logistical challenges make it hard to stick to long-term.
❌ Long-term health risks – High saturated fat intake and lack of fiber may increase heart disease risk.
Carnivore in Review
The Carnivore Diet is a powerful short-term tool for fat loss and muscle maintenance, but it’s highly restrictive and nutritionally imbalanced. While some athletes and biohackers swear by it, the long-term health effects remain unclear. It's effective for cutting fat and simplifying eating, but the extreme elimination of plant-based nutrients makes it difficult to sustain and potentially risky over time.
Rating: 6/10
Vegan Diet
Origin & History
The roots of veganism trace back thousands of years to ancient religious and philosophical traditions. Jainism, one of the oldest Indian religions, promoted a strict form of vegetarianism focused on non-violence toward all living beings (ahimsa). Early Buddhist and Hindu practices also emphasized plant-based diets as a way to minimize harm and purify the body and mind.
The modern vegan movement took shape in the mid-20th century. In 1944, Donald Watson, a British animal rights advocate, coined the term “vegan” to distinguish those who avoided not just meat but all animal products, including dairy, eggs, and honey. Watson founded the Vegan Society with the goal of promoting a diet and lifestyle that rejected animal exploitation entirely. His motivation was not just health-based but also driven by ethical concerns about animal cruelty and environmental sustainability.
The ethical and environmental appeal of veganism gained traction in the 21st century as scientific research highlighted the environmental cost of animal agriculture. Studies showed that meat and dairy production contribute to greenhouse gas emissions, deforestation, and water depletion. Ethical concerns over factory farming and animal treatment further fueled the rise of veganism. High-profile athletes, celebrities, and influencers adopting vegan diets helped push it into the mainstream.
What the Vegan Diet Involves
The vegan diet is entirely plant-based, which means no animal products of any kind. That includes:
- No meat – Red meat, poultry, fish, and seafood are excluded.
- No dairy – Milk, cheese, butter, and yogurt are off-limits.
- No eggs – No eggs or egg-based products.
- No honey – Since honey is produced by bees, it’s considered off-limits.
Instead, the diet focuses on:
- Whole grains – Brown rice, quinoa, oats, whole wheat.
- Legumes – Lentils, chickpeas, black beans, and edamame.
- Fruits and vegetables – Leafy greens, berries, citrus fruits, cruciferous vegetables.
- Nuts and seeds – Almonds, walnuts, chia seeds, and flaxseeds.
- Plant-based fats – Avocados, olive oil, and coconut oil.
Many vegans also rely on fortified foods or supplements to cover nutritional gaps, particularly for vitamin B12, iron, and omega-3s.
What Veganism Is Best For
- Reducing environmental impact – A vegan diet requires fewer natural resources and produces lower greenhouse gas emissions compared to meat-based diets.
- Lowering cholesterol and heart disease risk – Plant-based diets have been shown to lower LDL (“bad”) cholesterol and reduce the risk of heart disease.
- High fiber intake and digestive health – The abundance of fruits, vegetables, and whole grains supports gut health and regular digestion.
Pros
✔️ High in fiber and antioxidants – Promotes gut health and reduces inflammation.
✔️ Environmentally sustainable – Lower carbon footprint and reduced water usage.
✔️ Cardiovascular benefits – Linked to reduced blood pressure and improved heart health.
✔️ Weight loss – Higher fiber content and lower calorie density can make it easier to lose fat.
Cons
❌ Hard to get enough complete protein – Most plant-based proteins lack leucine, which is critical for muscle protein synthesis.
❌ Nutrient deficiencies – Low levels of B12, iron, zinc, and omega-3 fatty acids can impair energy, recovery, and muscle growth.
❌ Muscle-building limitations – Plant proteins are less bioavailable and less anabolic compared to animal-based proteins.
❌ Heavily processed vegan alternatives – Many vegan products (like faux meats and cheeses) are high in additives, sodium, and unhealthy fats.
Veganism in Review
Veganism offers significant benefits for heart health, digestion, and environmental sustainability, but it presents major challenges for muscle building and testosterone optimization. While it's possible to build muscle on a vegan diet, it requires careful planning, higher overall protein intake, and strategic supplementation. For fat loss and overall health, it's effective—but for muscle growth and strength, it’s lacking.
Rating: 5/10
Keto Diet
Origin & History
The ketogenic diet (keto) has been around for over a century, but its original purpose had nothing to do with weight loss or fitness. It was first developed in the 1920s as a medical treatment for epilepsy. Researchers discovered that fasting reduced the frequency of seizures in patients, and since fasting wasn’t sustainable long-term, doctors designed the ketogenic diet to mimic the metabolic state of fasting by shifting the body’s primary fuel source from carbohydrates to fats.
Dr. Russell Wilder at the Mayo Clinic is credited with developing the modern ketogenic diet in 1921. It became the standard treatment for epilepsy for decades, but the rise of anti-seizure medications in the 1940s and 1950s led to a decline in its use.
The keto diet resurfaced in the early 2000s as a tool for weight loss and metabolic health. Dr. Robert Atkins’ low-carb "Atkins Diet" laid the foundation for keto’s popularity. Researchers like Dr. Dominic D’Agostino explored the broader metabolic benefits of ketosis, including fat loss, insulin regulation, and mental clarity, which helped push keto into the mainstream fitness and biohacking communities.
What the Keto Diet Involves
The keto diet is characterized by a high-fat, moderate-protein, and very low-carb approach. The typical macronutrient breakdown looks like this:
- 70%–80% fat – Avocados, nuts, seeds, oils, butter, and fatty cuts of meat.
- 15%–20% protein – Moderate amounts of meat, fish, eggs, and cheese.
- 5%–10% carbs – Less than 50g of carbs per day, which severely limits grains, fruits, and starchy vegetables.
The goal of keto is to shift the body into a state of ketosis — where the body burns fat for fuel instead of glucose. When carb intake drops, glycogen stores deplete, and the liver starts producing ketones from fat as an alternative energy source. This shift reduces insulin levels, increases fat burning, and suppresses appetite.
What Keto Is Best For
- Fat Loss – Ketosis increases fat oxidation, making it easier to lose fat while preserving lean tissue.
- Appetite Control – The high-fat intake increases satiety and reduces hunger hormones like ghrelin.
- Improving Insulin Sensitivity – Lower carb intake stabilizes blood sugar and reduces insulin resistance.
Pros
✔️ Fast fat loss – Once ketosis is established, the body becomes highly efficient at burning fat for fuel.
✔️ Appetite suppression – High-fat meals are more satisfying, leading to reduced overall calorie intake.
✔️ Improved mental clarity and energy – Some people report sharper focus and sustained energy due to stable blood sugar levels and increased ketone availability.
✔️ Improved metabolic flexibility – Enhanced ability to switch between burning carbs and fats for energy over time.
Cons
❌ Muscle loss risk – The low carb intake can reduce muscle glycogen stores, which impacts strength and muscle-building potential.
❌ Reduced workout performance – Glycogen is the primary fuel for high-intensity exercise, and keto reduces glycogen availability, which can lead to decreased strength and endurance.
❌ Difficult to sustain long-term – The extreme carb restriction makes it hard to maintain keto socially and practically. Eating out or attending social events becomes challenging.
❌ Nutrient deficiencies and digestive issues – The low intake of fruits, vegetables, and grains can lead to low fiber, magnesium, and potassium levels, resulting in constipation and cramping.
❌ "Keto Flu" – In the early stages of keto, the body adjusts to lower carb intake, leading to fatigue, headaches, brain fog, and irritability.
Keto Diet in Review
Keto is highly effective for fat loss and appetite control, but it comes at a cost—strength, muscle retention, and workout performance suffer without glycogen. It's also difficult to sustain long-term due to its restrictive nature and social limitations. While it's effective for metabolic health and weight loss, it's not ideal for building muscle or sustaining intense training.
Rating: 6.5/10
Traditional High-Protein Omnivorous Diet (Winner)
Origin & History
Humans are, by nature, omnivores. Our ability to eat and digest both animal and plant-based foods is an evolutionary advantage that dates back millions of years. Early humans were hunter-gatherers, surviving on a combination of wild game, fish, fruits, vegetables, nuts, and seeds. The development of agriculture around 10,000 years ago introduced grains and cultivated vegetables into the diet, creating a more diverse and balanced nutritional foundation.
The traditional omnivorous diet reflects this evolutionary balance. Cultures worldwide have long relied on a combination of animal and plant-based foods for sustenance and health. From the Mediterranean diet (rich in fish, olive oil, and vegetables) to the Japanese diet (seafood, rice, and fermented foods), the omnivorous diet has stood the test of time as a balanced, nutrient-rich approach to eating.
In modern times, bodybuilders and strength athletes have relied on high-protein omnivorous diets for muscle growth and recovery. The foundation of successful strength programs — chicken, beef, eggs, fish, and nutrient-dense carbs — stems from the basic principles of a balanced omnivorous diet.
What the Traditional Omnivorous Diet Involves
A traditional high-protein omnivorous diet includes a balanced mix of:
- Protein: Meat, fish, eggs, poultry, and dairy – provides all essential amino acids and promotes muscle repair and growth.
- Healthy Fats: Avocados, nuts, seeds, olive oil, and fatty fish – supports hormone production (especially testosterone).
- Complex Carbs: Vegetables, fruits, whole grains, legumes – fuels workouts, supports recovery, and provides fiber and micronutrients.
- Minimal Processed Foods: Focus on whole, nutrient-dense foods while limiting refined sugars, seed oils, and processed snacks.
The goal is to create a macronutrient balance that supports muscle growth, strength, and hormonal health while providing enough micronutrients for overall health and longevity. A typical macronutrient breakdown looks like:
- 40% protein – Promotes muscle protein synthesis and recovery.
- 30% carbs – Provides glycogen for workout performance and energy.
- 30% fats – Supports hormone production, including testosterone.
What It’s Best For
- Building Muscle and Strength – The high protein intake supports muscle protein synthesis, while carbs fuel strength and hypertrophy training.
- Hormonal Balance – Fats and cholesterol from whole foods provide the building blocks for testosterone production.
- Long-Term Health and Sustainability – Provides a balanced mix of nutrients, supports digestive health, and reduces inflammation when focused on whole foods.
Pros
✔️ High in bioavailable protein – Animal-based proteins (meat, fish, eggs) contain all essential amino acids, making them superior for muscle-building.
✔️ Supports muscle growth and recovery – The combination of protein and carbs promotes muscle repair and glycogen replenishment.
✔️ Balanced macronutrient intake – Carbs fuel training, fats support hormone health, and protein builds muscle.
✔️ Sustainable long-term – Easy to adapt to different lifestyles and social settings without strict dietary limitations.
✔️ Nutritionally complete – Provides all essential vitamins and minerals (B12, zinc, iron, omega-3s, etc.) without the need for supplementation.
✔️ Flexible and Adaptable – Can be modified based on training goals, cutting, or bulking phases.
Cons
❌ Requires some planning – Success depends on food quality and balancing macros correctly.
❌ Food quality matters – Relying on processed meats, refined carbs, or low-quality oils can derail progress and increase inflammation.
❌ Overeating risk – Easy access to calorie-dense foods makes it easy to overconsume, leading to fat gain if not properly monitored.
Traditional Omnivorous Diet in Review
The traditional high-protein omnivorous diet strikes the best balance between muscle growth, strength, hormonal health, and long-term sustainability. It provides a complete amino acid profile for muscle repair, carbs for energy, and fats for hormone regulation — all while being flexible and easy to maintain in real-world settings.
When focused on high-quality whole foods, this diet delivers the best results for building muscle, boosting testosterone, and sustaining long-term health. The combination of nutrient density, satiety, and muscle-building potential makes it the superior choice for men over 40 looking to optimize their strength and physique.
Rating: 9/10
✅ Best for strength, muscle growth, fat loss, and overall health.
✅ The most sustainable and balanced approach.
✅ The clear winner for long-term success.
Final Review & Conclusion
Summary of Diets:
Carnivore Diet – Offers fast fat loss but is poor for long-term health due to its lack of diversity and potential nutrient deficiencies. Best for those seeking quick weight loss but not sustainable for muscle growth or hormonal health.
Vegan Diet – Provides heart health and environmental benefits but lacks the necessary components for muscle and strength. While rich in fiber and antioxidants, it falls short in providing the complete protein profile needed for optimal muscle growth and recovery.
Keto Diet – Excellent for fat loss and improving insulin sensitivity, but limits strength and muscle growth due to restricted carbs and the risk of muscle loss. Great for those looking to shed fat quickly but less effective in the long run for strength gains and muscle retention.
Traditional High-Protein Omnivorous Diet – The best overall for muscle growth, strength, hormonal balance, and long-term health. This diet offers a perfect macronutrient balance, with bioavailable proteins, healthy fats, and complex carbs, making it the most sustainable and nutritionally complete choice.
Why Traditional Wins:
- Best Macronutrient Balance – The combination of protein for muscle building, fats for hormone production, and carbs for energy fuels optimal health and performance.
- Most Sustainable and Socially Adaptable – Unlike restrictive diets like carnivore or keto, the traditional omnivorous diet is versatile and easily adaptable to different lifestyles, social settings, and cultural practices.
- Nutritionally Complete – This diet covers all essential nutrients, ensuring you avoid deficiencies in key vitamins and minerals like B12, iron, zinc, and omega-3 fatty acids.
Take Action:
For those over 40, focusing on a balanced, high-protein omnivorous diet is the most reliable approach to achieving long-term health, strength, and muscle growth. By combining high-quality animal and plant-based foods, you set yourself up for sustainable progress while maintaining a healthy lifestyle.
Want to get started? Check out our meal plans for building muscle after 40, explore high-protein recipes that are easy to incorporate into your routine, and dive into our recovery strategies to ensure you maximize your gains.
Related posts to help you get started:
- Best Diet for Muscle Growth & Fat Loss After 40
- The Ultimate High-Protein Recipes for Strength & Recovery
- How Sleep and Recovery Impact Testosterone and Muscle Growth
The traditional high-protein omnivorous diet is your best bet for optimal health and strength as you age. Start building a sustainable, balanced approach to nutrition today!