By Mukaila Kareem
Human metabolism did not evolve in a single environment. It was shaped across deserts and forests, savannas and shorelines, cold tundra and tropical canopies. Yet today, the Western ketogenic diet is sold as a universal blueprint for health, as if all humans evolved under the same ecological pressures and climates. This is understandable because modern medicine is Western oriented but nonetheless it is not excusable because it is false globalization. Keto is an Arctic survival mechanism and far from being tropical and confusing, the two have led to widespread misunderstanding of how human metabolism actually works.
In cold northern environments, where fruits, tubers, and fiber-rich plants were rare for most of the year, humans depended on seals, fish, and marine mammals for survival. In such settings, food scarcity was common, and the body evolved ketones as a backup fuel system. When blood glucose dropped and meals were delayed, the liver converted stored fat into an emergency brain fuel called beta hydroxybutyrate, a ketone molecule. But ancestrally, ketones were never meant to be chronic; but they were a biochemical distress signal. Because ketosis is a survival strategy, even the Inuit (also called Eskimos) did not live in permanent ketosis because of high protein intake, and their unique genetic adaptations resisted it. Ketosis in nature is a situational bridge across hunger to deter starvation and not a sexy lifestyle as it is often promoted.
Tropical humans evolved under entirely different pressures. Here, fibrous tubers, seasonal fruits, edible leaves, and starchy plants provided reliable sources of year-round fermentable carbohydrates to prevent long starvation episodes. More importantly, and totally under-appreciated by Western diet gurus, tropical diet is a two-stage digestive process. First, carbohydrates provide immediate energy in the small intestine where they are absorbed as simple sugars. Hours later, the second stage begins with gut microbes in the large intestine ferment resistant starch and insoluble fiber into short-chain fatty acids like butyrate as a delayed pulse of clean-burning fuel. This “second meal” stabilized metabolism and eliminated the need for starvation ketones. It is an elegant built-in continuity without a need for emergency signals and a reason why there has been no data on ketosis and ancestral tropical societies.
Unlike what the diet warriors preach, human metabolism is promiscuous. It has no loyalty to the bright, dogmatic red lines drawn between carbohydrates, proteins, and fats. The body simply makes what it needs from whichever fuel is available. This flexibility was the key to human survival, and it was shaped by ecology and not ideology. The tropical body thrived on fermentation-driven continuity, while the Arctic body relied on scarcity-driven ketones. Mistaking one for the other distorts the true story of human metabolism and survival.
Yet modern keto culture, now spreading rapidly in Nigeria, repeats the same error by adopting a climate-specific survival mechanism as universal wisdom. Many Nigerians now fear carbohydrates and embrace high fat eating as if “ancestral” health requires ketone production. But our ecological ancestry is tropical. Our metabolism evolved from cassava, yam, plantain, millet, maize, and fruits, a group of foods that feed gut based fermentation and not liver driven distress signal ketosis. Weight loss does not come from avoiding carbohydrates, it comes from giving the body time between meals to finish what it has already been fed and allowing the fermentation rhythm to function.
There is also a neglected cost of the constant fat traffic created by the keto lifestyle. After a high-fat meal, the intestine releases tiny “cargo ships” called chylomicrons to ferry fats in water-based bloodstream and they remain in circulation for hours. On a chronic keto diet, these ships flood the bloodstream all day, overwhelming the liver and raising triglyceride levels. Ironically, those who fear high glucose are often quick to excuse this nonstop lipid congestion in the bloodstream. Eventually a system designed for periodic fat pulses and not continuous oil transport pays a metabolic price. A swamp of fats in blood circulation is not better than a swamp of glucose and even modern medicine has a range of normal values for these substrates.
When metabolism is restored to its ecological context, the picture becomes clear. The Arctic relies on ketone bursts when food disappears. The tropics rely on “second meal” butyrate bursts produced hours after eating. One is an emergency bridge and the other is a continuity bridge. Neither was meant to be chronic. And no human population on earth has ever lived in sustained ketosis but many lived in sustained fermentation.
Before official US dietary guidelines appeared in 1977, humans did not need food rules. They simply lived close to the land and followed the rhythms of their ecology. The path to metabolic health today is not keto or low-carb dogma, and for the tropical urban dwellers, it is about rediscovering the natural timing, fiber-rich foods, and movement patterns that shaped the human body long before diet tribes existed.
Mukaila Kareem, a doctor of physiotherapy and physical therapy advocate, writes from the USA and can be reached via makkareem5@gmail.com
