We Weren’t Meant to Eat This Much Fat
Reclaiming Metabolic Health by Returning Fat to Its Proper Role
When most people picture ancestral diets, they imagine heavy meat consumption, rich animal fat dripping into fire, and a life of feasting on animal calories. But this image is misleading. For the majority of traditional societies studied by anthropologists, fat was not a staple fuel. It was rare, highly prized, and often consumed in the context of ceremonial feasts or seasonal abundance. Daily life was powered primarily by carbohydrates from fruit, tubers, honey, and other starchy plant foods, with lean animal protein supporting growth and repair. Fat was valued, but it was not the backbone of human nutrition.
The Carbohydrate Backbone of Ancestral Diets
One of the clearest examples of carbohydrate-based living comes from the Papua New Guinea Highlands. In this mountainous region, the sweet potato was not simply a side dish but the absolute centerpiece of the diet. Studies showed that the average adult consumed nearly one kilogram—about 956 grams—of sweet potato per day (Ohtsuka, 1983). That equates to more than 30 ounces, or three to five medium roots, yielding roughly 200 grams of carbohydrate.
But the sweet potato was not alone. Highlanders also consumed taro, yams, sugarcane, and bananas. Some surveys estimated that the total tuber intake exceeded 1000 grams daily, and that carbohydrate intake easily surpassed 500 grams per day. Energy intake in these populations has been estimated at 50–60 calories per kilogram of body weight, and yet obesity, diabetes, and cardiovascular disease were absent. These communities were lean, fertile, and active, with caloric intakes that would shock the modern dieter.
Protein came from small amounts of lean wild game, fish, or insects. Fat intake was extremely low, often under 10% of calories. Wild game typically contained only 4–7% body fat—far leaner than modern feedlot beef, which can exceed 30%. This alone reveals the distortion of our modern food supply: the fatty meat we take for granted was virtually absent in nature.
Feasts, Not Foundations
Fat did appear, but in a very different context. It was concentrated in ceremonial or celebratory feasts. In the Highlands, when a pig was slaughtered, the entire community gathered. For those few days, fat intake might soar to 30–40% of calories. Organ meats, marrow, and the precious fat were consumed in large amounts. But this was temporary. Once the feast ended, the population returned to their carbohydrate-rich baseline of sweet potatoes, taro, and bananas.
This rhythm shaped human biology. Fat was rare, so our brains evolved to crave it intensely when it appeared. Eating extra was adaptive—it provided survival insurance in uncertain food environments. But in the modern world, that ancient craving is constantly triggered. We live in a permanent feast, with processed foods delivering fat and sugar layered together at every corner store. This mismatch—ancestral scarcity versus modern abundance—explains why fat feels addictive and why moderation is so difficult.
The Eight Cultures Weston A. Price Studied
Nutrition pioneer Weston A. Price traveled the world in the early twentieth century, documenting the diets of traditional peoples. He identified eight cultures in depth. Seven thrived on diets that were low in fat and high in carbohydrates. The only exception was the Inuit, who lived in extreme environments with little plant food.
The Inuit diet, while high in animal fat, came with significant costs. Their fertility was lower, miscarriage rates higher, and life spans shorter than those of their high-carb counterparts. They experienced metabolic strain, and their survival strategy—relying on fat and protein in the absence of plant foods—was not an optimal diet, but a necessary adaptation to a harsh environment.
This is the critical lesson: high-fat, low-carb diets such as keto or carnivore are survival diets. They can sustain life when no other food is available, but they are not the ideal pattern for fertility, longevity, or metabolic resilience. Just as the Inuit accepted trade-offs to endure their climate, modern high-fat diets may help people endure short-term goals, but they come with long-term costs.
Humans Are Carbohydrate-Eaters
Biologically, humans are primates. And primates are overwhelmingly frugivores: fruit eaters. From chimpanzees to bonobos, primates thrive on fruit, tubers, leaves, and occasional small animals or insects. Humans are no different. Our physiology is built for carbohydrate metabolism.
The Hadza of Tanzania are a striking example. They consume honey ten months of the year, demonstrating that sweetness was a constant in the human story (Pontzer et al., 2018). Carbohydrates were never “junk” in an ancestral setting—they were the essential energy source that powered thyroid function, reproductive hormones, and brain activity. When we deprive ourselves of carbs, thyroid output drops, body temperature falls, and fertility declines. Carbohydrates are not optional; they are the fuel that drives human metabolism.
How We Got Lost: Tobacco Companies, Seed Oils, and Swampland
The modern diet is not the result of natural evolution but of corporate engineering. In the 1980s, tobacco companies such as Philip Morris (which bought Kraft and Nabisco) and RJR Nabisco (which absorbed General Foods) purchased food conglomerates. They applied the same playbook they had perfected with cigarettes: engineer products to maximize addiction.
The result was processed food that combined refined flour, sugar, and industrial seed oils. Americans were told to “fear carbs,” but most of the foods we casually label “carbs” are not carbohydrate foods at all. Pizza, donuts, cake, cookies, ice cream, nachos, and creamy pasta are 60-80% fat calories. These are hybrid foods: high fat plus moderate carbs.
This is swampland. Swampland is the zone where fat intake is high enough to block carbohydrate metabolism, while carbohydrate intake is still too low to protect thyroid and metabolic function. In swampland, fasting insulin rises, fat storage accelerates, and energy stalls. Seed oils exacerbate the problem, damaging mitochondria, thyroid hormone signaling, and cellular metabolism.
Everyone has their own “personal swampland,” the fat threshold at which their metabolism slows, insulin resistance appears, and weight creeps upward. Blood tests such as fasting insulin or HOMA-IR reveal when you’ve crossed into this territory. Carbs must be high enough to keep the system running. Fat must be low enough to prevent metabolic bog.
Fat as Dessert, Not Dinner
The ancestral lesson is clear: fat was never daily fuel. It was dessert, the rare feast food. Daily life was starch, fruit, honey, and lean protein. Fat was occasional, precious, and temporary.
To thrive today, we must relearn how to fall in love with carbs without fat. Real carbohydrate foods include fresh fruit and dried fruit, potatoes and other tubers, fruit juice, honey and maple syrup, lemonade and Italian sodas made with cane sugar, and—where tolerated—white rice, sourdough bread, sprouted oats, and masa harina tortillas. These foods deliver glucose without fat, fueling the thyroid and metabolism.
For modern application, keeping fat around 0.3 grams per kilogram of lean body mass—roughly 10–20 grams per day for women and 15–25 grams for men—functions as a reset phase, restoring insulin sensitivity and reversing weight gain. This can be sustained for one to two months, similar to the logic behind the Kempner Rice Diet. Long term, 0.5 g/kg makes a more sustainable baseline, with weekly or occasional feast days at 0.6–0.8 g/kg. This cycle mirrors the ancestral pattern: low fat most days, higher fat during rare feasts.
References
Ohtsuka, R. (1983). Nutritional adaptation of highland populations in Papua New Guinea. PubMed
Pontzer, H. et al. (2018). Energy expenditure and diet among Hadza hunter-gatherers. NCBI
Eaton, S. B., & Konner, M. (1985). Paleolithic nutrition. New England Journal of Medicine.
MDPI (2024). Worldwide hunter-gatherer diet macronutrient survey. MDPI
Chris Kresser. Kitavan macronutrient breakdown. Kresser
