Coach — Metabolic Hypothesis of Fuel
This pillar sits on the Shore: Living Water.
Food is not a number on a label. It is a daily contract with two very old partners, and most modern menus break it.
Every diet book needs a villain and a hero. Fat or sugar, meat or plants, calories in or calories out. The quarrel is loud because the frame is small. It pictures a person as a single furnace and food as a pile of logs, then argues about which logs burn best.
The working hypothesis here starts somewhere older. A human being does not eat alone. Inside nearly every one of your cells sit mitochondria, descendants of free-living bacteria that were taken in by an ancestral host cell long ago and never left. They still carry their own small circular genome, their own membranes, and their own preferences. Outside your cells, in the gut, lives a second partner: a dense community of bacteria and archaea whose combined genes vastly outnumber yours. That community does chemistry you cannot do, unlocking plant fibers and turning them into short-chain fatty acids that feed the lining of the colon and help set the tone of the immune system.
Fuel, in this view, is not a question of calories. It is whether what you eat, and when you eat it, respects that nested partnership or assaults it. Get the substrates and the timing roughly right, and many of the numbers medicine chases downstream start to look less mysterious. Get them wrong for years, and the body's emergency systems stay switched on long after the emergency should have ended.
Two kitchens in one house
Think of the body as a house with two kitchens. The inner kitchen belongs to the mitochondria. The outer kitchen belongs to the gut community. Each was stocked over evolutionary time with particular ingredients, and each cooks badly when handed the wrong ones.
The inner kitchen still carries the habits of its bacterial ancestry. It is built for the orderly burning of fatty acids, for making ketones when glucose runs low, and for feeding amino-acid fragments into its central cycle when demand calls for them. Animal fats, particularly the saturated and monounsaturated kinds found in ruminant fat and egg yolk, burn there in an orderly way, without the backed-up chemistry that a flood of fast sugar tends to create. Ketones, which the liver makes from fat when carbohydrate is scarce, are not a desperate backup. The brain, heart, and muscle readily use them, and they carry signals of their own.
Animal foods also bring building materials. Cholesterol and relatively saturated membrane fats help pack the inner membrane where the energy work happens. Cardiolipin, the signature fat of that membrane, needs the right fatty-acid makeup for the respiratory machinery to assemble properly. Animal protein arrives as a toolkit rather than mere bricks: complete amino acids, leucine dense enough to switch on muscle building, creatine to buffer energy in working muscle, carnitine to ferry long-chain fats into the mitochondria, taurine and glycine for repair and defense. The body can make some of these itself, but only in limited amounts.
The outer kitchen works differently. The human genome carries only a handful of enzymes for breaking down the tough sugars in plant cell walls. Gut microbes carry dozens to hundreds per species. They ferment those fibers into butyrate, propionate, and acetate. Butyrate matters most here: the cells lining the colon draw most of their energy from it, roughly sixty to seventy percent by the estimates cited in this hypothesis. Butyrate helps keep the junctions between those cells tight, keeps the mucus layer thick, and helps train the immune system toward tolerance. When butyrate falls, the barrier loosens, bacterial fragments slip into the blood, and a low, steady inflammation follows.
Here is the catch. Refined flour and sugar are absorbed high in the small intestine, long before they reach the colon. They feed you quickly and the outer kitchen hardly at all.
Fermentation as pre-digestion
Traditional cooks solved this problem without knowing they had it. Fermentation is pre-digestion. When cabbage becomes sauerkraut or kimchi, or milk becomes yogurt or kefir, the fermenting microbes eat much of the free sugar and lactose first. What remains is a matrix of organic acids, small bioactive peptides, some B vitamins, sometimes vitamin K2, and a residue of fiber that the colon's own microbes can still use.
Mushrooms play a bridging role. Their beta-glucans and chitin-like fibers barely register with human enzymes, yet particular gut bacteria ferment them readily, and they tend to favor the butyrate makers. They are neither quite host food nor quite microbial food. They are a message passed between the two kitchens.
So in this hypothesis, sauerkraut, kimchi, yogurt or kefir where tolerated, and ordinary culinary mushrooms are not garnish. They are how you feed the outer partner without flooding the small intestine with fast sugar.
A hierarchy, not a ban
None of this says never eat plants. It proposes a hierarchy. Animal fats and proteins as the main fuel for the inner kitchen. Fermented plant carbohydrates and mushrooms as the main fuel for the outer one. Glucose as a fast fuel for acute demand, not an all-day stream. And three ingredients treated as chronic stressors: refined sugar, industrial seed oils, and alcohol.
An exclusively plant-based diet can be built toward adequacy with care. It takes complementary proteins, attention to the type of fat, fermented foods, and supplements for what plants do not supply, such as B12 and algae-derived long-chain omega-3s. The cost is engineering. The body converts plant omega-3 into the long-chain forms poorly, often below five to ten percent. Plants contain essentially no creatine and little carnitine or taurine, and no cholesterol. Preformed vitamin A, B12, the longer forms of K2, and the most absorbable iron come mainly from animal foods. That is a biochemical observation, not a moral ranking of people. Someone who eats plant-forward for conscience or culture can do well. The hypothesis only says the package does not arrive pre-assembled.
The jellyfish
In the ocean, a jellyfish rarely kills you outright. It stings, and the sting keeps working. The three modern ingredients this hypothesis worries about most behave the same way.
Refined sugar in chronic excess pushes more electrons into the mitochondrial chain than it can handle when the cell has little demand. Electrons leak, and the leak makes reactive oxygen species that damage mitochondrial DNA, proteins, and fats. Glucose also binds to proteins without asking, forming glycation products that feed inflammation. Constantly high insulin then blocks fat burning and ketone production, locking the body into dependence on sugar even when fat is plentiful. The liver turns surplus sugar into fat. In susceptible people the pancreas eventually tires. Inflammation and fatty liver then look like separate diseases when, on this reading, they may be predictable compensations.
Industrial seed oils, the high-linoleic soybean, corn, sunflower, safflower, canola, and cottonseed oils, are a new ingredient at today's volumes. Their fragile polyunsaturated fats slip into cell and mitochondrial membranes in place of sturdier ones. There they oxidize easily, setting off chain reactions that produce reactive aldehydes, which then damage the very proteins of the energy chain. When omega-3 intake does not keep pace, the balance of signaling molecules made from these fats tilts toward inflammation. These oils enter the ledger as fat, yet they degrade the room where fat is supposed to burn cleanly.
Alcohol, in this map, is a direct mitochondrial and gut-barrier toxin. Breaking it down floods the cell with one form of a key energy carrier, NADH, which stalls the central energy cycle and fat burning. Its first breakdown product, acetaldehyde, sticks to proteins and DNA. Regular drinking ramps up a liver pathway that makes still more reactive oxygen, loosens the gut barrier, and fragments sleep. It is not a neutral calorie.
The practical instinct follows: subtraction before stacks. Stop the jellyfish before buying another antioxidant or mitochondrial booster.
Timing is part of the meal
Fuel is also a matter of when. Cortisol rises in the early morning, mobilizing energy for the day. Insulin sensitivity tends to be higher earlier in the day. As evening comes, the body shifts toward repair: growth hormone, the cleanup of damaged cell parts and worn-out mitochondria, and the recovery of the gut community, all of which work best without food arriving.
Late eating, especially within about four hours of habitual bedtime, is hypothesized to keep night-time glucose and insulin high, blunt the evening fall in cortisol, fragment sleep, shrink the window for growth-hormone repair, and flatten the whole daily rhythm. The hypothesis describes a consistent daytime eating window, often in the eight-to-twelve-hour range, that ends well before sleep. That is time-restricted eating as daily hygiene, not a heroic fast, and it is described here as information rather than an instruction. Longer fasts belong under your own physician's judgment, especially with diabetes medications, pregnancy, a history of eating disorders, or frailty.
Composition and timing reinforce each other. Meals built around protein and fat tend to produce steadier blood-sugar curves than large sugary meals, which can overshoot into a dip and a stress-hormone correction. The same ingredients that help or hurt the mitochondria also shape the daily hormonal clock.
What the body reports
If this hypothesis is right, the useful signals are upstream ones, read together rather than one at a time. Fasting insulin and the ratio of triglycerides to HDL say more about the insulin economy than glucose alone. Liver enzymes can hint at fat building up in the liver. Inflammatory markers such as hs-CRP, and an omega-3 index where available, sketch the membrane story. Cheaper still are consistency of sleep timing, morning energy against evening wired-and-tired, and the trend of resting heart rate. These are weather reports for the partnership, worth reviewing with your own physician. They are not enemies to silence with the first drug that moves a number.
Readiness without app religion
Food apps and wearables can show patterns. They do not turn this page into a prescription pad. Use them briefly, then return to grocery geometry and subtraction. Hypothesis language stays on purpose.
Imperfect weeks
Real life breaks patterns. Coach for the week’s weather, not purity theater on Tuesday. Return to the hierarchy when the constraint lifts — without self-attack rituals that become their own stressor.
Extras after the foundation
Creatine, ketone strategies, and well-timed caffeine all have a place in this hypothesis, but as extras on a solid foundation. They amplify. They do not replace. Taking creatine and caffeine on a diet of seed oils, candy, and midnight snacks is a failure mode, not a shortcut. The short guide to these extras sits elsewhere on this site, and the neighboring essay on signals follows caffeine into the body's energy alarms.
One field, two dashboards
It is tempting to turn gut and mitochondria into rival religions, fiber maximalists on one side and carnivore absolutists on the other. They are better read as two dashboards of one energy economy. Fuel is what you put into both.
The hypothesis does not prove that any disease will reverse, and it does not replace care from a cardiologist, endocrinologist, or oncologist. Genetics, medications, culture, budget, and the meaning of the table all matter. If you are already being treated for a condition, do not stop medications or chase a metabolic cure because of an essay.
What it does offer is an order of operations, and the order is frugal. The highest-leverage moves cost the least: protein and fat you can actually buy and cook, fermented vegetables and mushrooms as the default carbohydrate, the jellyfish removed, meals eaten while it is light. No exotic stack is required to begin. The partnership is still there, and so are the foods it was built on.
For the longer argument, with its full mechanism, read the extended report on fuel. For a short version, see Fuel in brief. Other essays are collected on the essay index.
A working hypothesis, open to correction and revised as new evidence arrives. Last revised October 17, 2026.
See the notice at the top of this page. Working hypothesis, not medical advice.
Related: HydroEye on Surf Shop (sold through MDVite, EnSurf LLC’s store; not manufactured by EnSurf). More on HydroEye: Coach · Surfer.
Related: Coach — Dry Eye and the Ocular Surface (Wipeouts · Ophthalmology).