From Population Requirements to Personal Nutrition Calibration | Part III
A Three-Part Series Introducing Nutrition from First Principles
Yes, I’m ready. Here’s the complete Part 3:
Why Nutritional Science Can’t Tell You What to Eat | Part 3
A Three-Part Series Introducing Nutrition from First Principles
The first two parts questioned nutritional science’s starting point and explored why asking “what should humans eat” leads to different answers than “what can humans eat.” Welcome back.
Now comes the moment every client describes: standing in their kitchen at 6 PM, staring into the refrigerator, paralyzed. They know more about macronutrients, inflammatory foods, and metabolic pathways than their grandparents ever learned. They can recite the glycemic index of every item in their pantry. But they have no idea what to make for dinner.
The kale makes them feel virtuous and bloated. The sweet potato sends their energy crashing two hours later. The grass-fed beef fits their protocol but leaves them reaching for something they can’t name. Every choice carries the weight of optimization—did they pick the most anti-inflammatory option? The most nutrient-dense? The one their latest lab results suggest?
Meanwhile, their body keeps sending signals they’ve learned to override. Cravings get dismissed as bad habits. Fatigue gets blamed on insufficient willpower. The conversation between what they know and what they feel grows louder until eating becomes a daily exercise in managing competing theories instead of nourishing an actual human system.
Here’s what it looks like when you stop asking “what’s optimal” and start asking “what’s sustainable”—when constraint-based reasoning meets your actual hunger at your actual kitchen counter.
From Theory to Kitchen Counter
The constraints that govern human nutrition—the protein ceiling, the Randle cycle, the isotopic evidence from bones, the metabolic mechanisms we explored last time—operate the same whether you’re standing in that kitchen or reading research papers. They don’t shift with dietary trends or expert disagreements. They simply are.
When you understand these constraints, the paralysis in front of the refrigerator starts to dissolve. Not because you’ve found the perfect diet, but because you can see which approaches respect metabolic reality and which create contradiction. Here’s what emerges when we examine common dietary patterns through this lens:
What Emerges
When biochemical constraints, historical evidence, metabolic mechanisms, and individual verification converge, a pattern emerges. Not a prescription, but what the constraints permit and what they eliminate.
The constraints don’t dictate a single diet. They reveal a spectrum of what’s mechanistically possible.
Where you belong in that spectrum depends on your genetics (AMY1, lactase, APOE), your activity level, your current metabolic health, and what you can verify through direct experience.
Here’s what happens when we examine common dietary patterns through the constraint lens, not to find “the answer,” but to see which approaches respect the constraints and which violate them.
What the Constraints Reveal About Popular Diets
Ketogenic (70-75% fat, 20-25% protein, 5-10% carbs)
Aligns with: Protein ceiling stays respected. Randle cycle operates in one clear mode, fat oxidation without glucose interference. Matches isotopic evidence from Paleolithic populations and historical Inuit diets.
Works because: Metabolically coherent. Forces fat adaptation, which humans demonstrably can do given preserved ketogenic machinery.
Watch for: Adequate micronutrients, especially if plant foods minimized. Individual tolerance varies. Some people feel exceptional, others struggle with energy during adaptation (typically 2-4 weeks).
Paleo (30-40% carbs, 30-40% fat, 20-30% protein)
Aligns with: If carbs come from tubers, fruits, properly prepared nuts, respects both historical evidence and avoids refined carbohydrate metabolic disruption. Protein within ceiling. Fat adequate for satiety.
Works because: Resembles the variable plant intake shown in archaeological sites with seasonal shifts. Avoids processed seed oils and refined grains that create inflammatory problems.
Watch for: Modern “Paleo” often becomes too lean. Boneless skinless chicken breast with sweet potato misses the ancestral fat emphasis. Also, calling it “Paleo” while eating foods that didn’t exist until agriculture deserves skepticism about the label even if the approach works.
The plants we eat today bear little resemblance to what our ancestors encountered. Modern vegetables have been selectively bred for millennia to increase sweetness, reduce bitterness, and maximize edible portions. A wild carrot is thin, pale, and intensely bitter. A wild banana is full of seeds and barely edible pulp. Even leafy greens have been cultivated to reduce defensive compounds that made them unpalatable.
This matters because the “Paleo” label suggests eating what Paleolithic humans ate, but the agricultural breeding that created modern produce is precisely what the Paleolithic period lacked. The body’s relationship to a modern sweet potato, engineered for high starch content, differs from its relationship to wild tubers that were smaller, tougher, and less calorie-dense.
This doesn’t invalidate eating vegetables. But it does complicate the narrative that we’re “eating like our ancestors” when the foods themselves are agricultural products.
Mediterranean (35-40% fat, 40-45% carbs, 15-20% protein)
Aligns with: Populations with high AMY1 copy number and long olive oil tradition. Fat is predominantly monounsaturated, carbs are whole foods (not refined), protein moderate.
Works because: For those with genetic adaptation to higher starch intake, this respects individual calibration while avoiding metabolic incoherence. The key is that it’s not low-fat-plus-high-carb-plus-seed-oils. It’s moderate-fat (from quality sources) with whole-food carbs.
Watch for: “Mediterranean diet” in practice often becomes pasta with low-fat marinara and bread, losing the actual fat content and whole-food emphasis that makes the pattern work. The research showing Mediterranean benefits studied people eating whole fish, olive oil, nuts, vegetables, not Olive Garden.
Carnivore (70-80% fat, 20-30% protein, 0-5% carbs)
Aligns with: Extreme version of ancestral pattern. Protein ceiling respected if emphasizing fatty cuts. Forces complete fat adaptation. Historical precedent in Inuit and high-latitude populations consuming primarily animal foods.
Works because: Eliminates all plant antinutrients (lectins, oxalates, phytates), removes fiber-related issues for those with gut sensitivity, creates maximum metabolic clarity with no mixed fuel signals.
Watch for: Requires attention to organ meats for micronutrients (vitamin C in fresh liver, folate in organs). Long-term effects beyond traditional populations less studied. Some people thrive indefinitely, others need strategic reintroduction of plants after gut healing.
Vegan (10-15% fat, 10-15% protein, 70-80% carbs)
Aligns with: Difficult to reconcile with constraints. Contradicts 2 million years of isotopic evidence. Requires supplementation (B12, often iron, zinc, omega-3s as EPA/DHA, sometimes vitamin A as retinol not beta-carotene). Protein sources are incomplete, requiring careful combining. Often forces higher carbohydrate intake by necessity.
Works because: Modern humans can survive on it with supplementation and careful planning. Some populations (like certain Indian groups) have practiced vegetarianism for millennia and show genetic adaptations. Agricultural societies demonstrated humans could survive grain-heavy diets, though often with trade-offs in height and bone density.
Watch for: Protein adequacy (particularly essential amino acids), nutrient gaps requiring supplementation, potential for high refined carbohydrate intake if relying on processed vegan foods. For some people with specific gut issues or autoimmune conditions, elimination of animal products does provide symptom relief, though this may indicate food quality issues (factory-farmed meat, conventional dairy) rather than animal foods inherently.
The modern vegetable cultivation issue compounds here. Vegan diets rely heavily on plant foods, but those foods are agricultural products bred for characteristics that didn’t exist in the wild. A vegan diet built on modern sweet fruits, starchy vegetables, and processed grains represents an even further departure from the constraints than an omnivorous agricultural diet. The body is being asked to run primarily on fuel sources that were either absent or minimal during the period when its metabolic machinery was being shaped.
Standard American Diet (35% fat, 50% carbs, 15% protein)
Aligns with: Nothing. This is the metabolic incoherence case study.
Fails because: High enough in both fat AND refined carbohydrates to create maximum Randle cycle confusion. Insulin rises from carbs (signaling fat storage) while dietary fat provides storage substrate. Neither commits to one metabolic mode. Seed oils high in omega-6 create inflammatory cascade. Refined carbs spike insulin repeatedly. Protein often inadequate, from processed sources.
This is neither the fat-centric pattern humans evolved with nor the whole-food-carbohydrate pattern some agricultural societies adapted to. It’s metabolically unprecedented. We have no ancestral template for handling this combination, and the results show in metabolic syndrome rates.
What This Reveals
The constraints don’t dictate a single diet. They reveal a spectrum of what’s mechanistically possible:
Fat-dominant approaches work if protein stays moderate and carbs stay low (respects Randle cycle, protein ceiling, historical precedent)
Carb-moderate approaches work if fat stays adequate and carbs stay whole-food (respects energy needs, avoids metabolic incoherence, allows individual calibration)
Carb-dominant approaches require genetic adaptation and careful attention to protein/fat adequacy (harder to reconcile with ancestral evidence but demonstrably survivable)
What doesn’t work: The modern mixed approach of high refined carbs plus high seed oils plus inadequate protein. This violates metabolic coherence and has no historical precedent. The constraints eliminate it before any clinical trial runs.
Where You Belong
If you have high AMY1 from agricultural ancestry: Consider increasing carbohydrates to 20-30%, reducing fat to 50-60%, including properly prepared grains like rice or oats.
If you have lactase persistence: Full-fat dairy products become available as options: yogurt, cheese, butter from grass-fed sources.
If you have APOE4: Consider emphasizing fish and olive oil over red meat, including more plant foods.
If pregnant or lactating: Increase overall calories by 300-500, prioritize DHA-rich fish and iron-rich organ meats, aim for 1.5g protein per kg body weight. Female reproductive requirements shaped food-seeking behavior more strongly than male reproduction because female fertility requires adequate body fat (typically 20-25%), specific micronutrients like iron and folate, and high energy availability. Male reproductive capacity extends decades longer, making it less nutritionally sensitive.
If you’re an athlete: Consider increasing protein slightly toward 2.0g/kg and adding strategic carbohydrates around training.
If you’re reversing metabolic syndrome: Consider starting with 60-70% fat, 10% carbs, monitor fasting glucose and triglycerides, expect metabolic adaptation over 4-8 weeks.
For detailed implementation guidance (meal planning, sourcing, preparation techniques), those resources exist elsewhere. This essay establishes the filters for discernment, not the menu for compliance.
From “Should” to “Can” to Clarity
The protein ceiling operates in every human liver. Energy density follows from thermodynamics. Isotopic signatures can’t misreport. Metabolic cycles are observable in any laboratory.
These aren’t opinions. They’re constraints that can’t be violated.
Each constraint eliminated possibility spaces. The protein ceiling rules out lean-meat diets. Energy density explains fat prioritization. Isotopic evidence shows 2 million years of apex predator trophic levels. The Randle cycle reveals why modern high-carb plus high-fat creates metabolic dysfunction. Genetic variation shows where individual calibration matters. Direct experience completes verification.
When these constraints converge, contradiction dissolves. Not because someone declared victory, but because the constraints themselves leave little room for alternatives.
This is what “can” reveals. Not what someone says you should do, but what the human body can actually tolerate, what the evidence shows actually happened, what metabolic mechanisms can actually sustain.
The method applies beyond nutrition. When examining gut dysbiosis, we don’t just prescribe probiotics and hope. We look at what’s mechanistically blocking microbial balance (opportunistic bacteria, low stomach acid, circadian disruption) then address those constraints. When working with emotional processing, we don’t rely on unverifiable energy healing. We use the direct, felt experience of emotional resistance dissolving, something verifiable without faith.
The same filters work whether interpreting a stool test or processing a limiting belief. Start with constraints. Build from mechanisms that don’t require belief. Verify through direct experience.
This creates a different kind of trust. Not trust in a practitioner’s authority or a dietary ideology, but trust in mechanisms that operate independently of belief. When something works, you understand why. When something doesn’t work, you have the literacy to adjust rather than abandon the entire approach.
Beyond Prescription
The point isn’t the diet. The point is replacing “should” with “can.”
Nutritional confusion wasn’t unique to food. It’s a pattern that appears anywhere rapid change outpaces the tools designed for slower-moving systems. Climate science, economic policy, public health: domains where observational studies contradict, expert consensus shifts, and intelligent people find themselves paralyzed by competing claims.
The solution isn’t better opinions. It’s harder constraints.
Ask what’s actually possible given limits that don’t change. Ask what the evidence shows actually happened. Ask what mechanisms can actually sustain. Ask what you can verify through direct experience.
When these layers converge, clarity emerges. Not all at once. But structure becomes visible. You see what’s mechanistically possible and what isn’t. You see what evidence shows versus what gets claimed. You see where individual variation matters and where it doesn’t.
This prevents the pattern that plagued my own journey and nearly every client who arrives depleted: expert dependency that never resolves, metric obsession that replaces felt experience, symptom management that ignores blocks, unverifiable beliefs that can’t be questioned, ideology requirements that gatekeep recovery, practitioner dependency that prevents autonomy, information overwhelm that leads to paralysis.
These aren’t inconveniences. They’re how helping becomes harm.
Constraint-based reasoning interrupts that cycle. Not by rejecting expertise, but by making it transparent and verifiable. You’re not asked to believe. You’re shown the constraints, given tools to verify them, and trusted to calibrate within the boundaries they create.
This isn’t about finding the one true diet. It’s about what happens when you stop asking “what should I eat?” and start asking “what can I eat?” The kitchen paralysis dissolves not because you’ve found better nutritional information, but because you’ve shifted to a different kind of question entirely.
The constraints that govern human nutrition don’t change based on the latest study or expert opinion. They operate the same in every metabolic pathway, regardless of dietary trends or professional disagreements. When you align with those constraints and use your direct experience to calibrate within them, the contradiction disappears.
Nutritional science created confusion by starting from the wrong question. Constraint-based reasoning starts from what cannot be otherwise, then trusts your system to reveal what works within those boundaries. The method matters more than any single conclusion. But the clarity that emerges when method and experience align tends to surprise people who’ve only encountered nutrition through “should.”
References
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