Constipation on carnivore means you've gone lean, and the cure is the thing the diet was supposed to be built on in the first place. Meat is almost entirely absorbed. There's very little left over to pass, so a carnivore going once a day or once every two days, comfortably, isn't constipated. That's what happens when food stops being mostly packaging. The bran that used to bulk everything out was never doing you a favour; it was a cargo you paid to carry through. The actual complaint, hard, dry, an effort, is a different thing, and it has one cause. Fat. Fat is what moves the gut. A fatty meal tells the gallbladder to empty, bile goes in, and bile is the body's own laxative, which is why a pound of lean steak sits like a brick and the same steak with the cap on and a knob of butter melting over it goes through like it was expected. Lean mince, chicken breast, egg whites and a tin of tuna is a plate with the plumbing turned off, and the person eating it blames the meat. So the fix is never fibre and never a sachet. It's the butter you were told to leave off, the 20% instead of the 5%, cream in the coffee, the fat cap eaten first. Within a day or two the problem has gone, and it stays gone as long as the plate shines. Which is the point. A diet of meat only works when the fat is on it. Take the fat off and you have a bodybuilder's cut with worse manners, and the gut is the first thing to file a complaint. Carnivore is high fat by definition. The bathroom is where people find that out.

Every time your body is left alone it switches to ketones, and every time it is interrupted it switches to sugar, which tells you which one is the setting and which one is the interruption. You are born in ketosis. The fattest baby on earth, running its brain on ketones from day one, before anyone has handed it a biscuit. You sleep in ketosis. By the early hours the liver is making ketones every night of your life, and the morning tiredness is the cereal switching them off. You fast in ketosis. Miss two meals and the liver is already turning fat into fuel, and the brain takes it without a murmur. You hunt in ketosis. Every persistence hunter who ran an antelope down over a day did it on fat, because nobody carries 20,000 calories of sugar on a run. You winter in ketosis. Every northern people for two million years spent the dark months on meat, fat and the stores on their own body. You spend an illness in ketosis. Appetite goes, the body stops asking for food, and it runs on fat while it repairs. Sugar is the fuel of the meal. Ketones are the fuel of everything in between, which is most of a life. The sugar engine was never the default. It was the thing the orchard switched on for a fortnight in August. The factory setting is the one you wake up in, before the toast puts you back on the other one.

Your body was built to chase an animal until it dropped, and the chimpanzee's was built to sit in a fig tree. You: - Sweat glands at ten times the chimp's density - A long, springy Achilles tendon - A nuchal ligament to steady your head at a run - A backside built for running - An arched foot The chimp: - A tenth of your sweat glands - An Achilles tendon barely worth the name - No nuchal ligament - Barely a backside - Flat feet The animals that share that neck ligament with you include the dog and the horse. The chimp and the pig go without. The lettuce has never once tried to run away.