Fasting

Fasting is one of the oldest interventions humans have. It’s also one of the most badly executed in modern hands, because most modern bodies are so metabolically broken that asking them to skip a meal feels like a medical event. It doesn’t have to be that way. Fasting works with the body, not against it, when the body is set up to receive it. Mine is. I don’t fast cold, I don’t fast carelessly, and I don’t fast as a punishment. I fast as a planned step in a stack, and I pair it with recovery on the other side so the system gets the full benefit of both.

This is how I do it.

The carnivore baseline

I am already in ketosis most of the time. I am a strict carnivore — see Carnivore — which means my glycogen stores are running low as a steady state, my insulin is floor-low, and my body is not sitting on a sugar cushion waiting to be drained. Most people who try to fast are starting from a metabolic state where the body has spent the last decade preferring glucose, hoarding it, and refusing to switch fuel sources without a fight. They get headaches. They get hangry. They get shaky. Their muscles get raided for amino acids to make glucose, because the body still believes glucose is the only currency. That is not a fast. That is a controlled metabolic crisis.

A fat burner does not have that problem. The switch has already happened. Ketones are already flowing. The fast is a continuation of what the body was already doing, not a violent reroute. This is the unspoken reason people who try fasting on a standard American diet usually fail and people who try it on carnivore usually do not. The work was front-loaded into the diet.

Zone 2 as a primer

The day or two before I fast, I push my zone 2 cardio. Steady, conversational, two-zone-out-of-five effort, long enough to drain the tank. Zone 2 is the cleanest way I know to burn through residual glycogen without trashing the body — it does not crater recovery the way a hard interval session would, it does not spike cortisol, and it tells the mitochondria the work assignment for the next several hours: oxidize fat, oxidize fat, oxidize fat. It is the gentlest, most aerobic version of “get ready.”

By the time I start the fast, I am not starting from full. I am starting from already half-empty. Ketosis deepens within hours instead of a day. Autophagy kicks in earlier — autophagy being the cellular cleanup process where the body cannibalizes its own broken parts, recycles damaged proteins, and chews through dysfunctional mitochondria, which is one of the actual mechanisms by which fasting earns its longevity reputation. The faster I get there, the more time I spend in the productive part of the fast instead of the runway.

This is the trick most fasting protocols leave on the table. They tell you to fast for sixteen hours, twenty-four hours, seventy-two hours — durations that assume a starting glycogen state nobody specifies. If you start full, half your fast is just burn-down. If you start drained, the entire fast is the productive phase. Same calendar time, very different biology.

Why this is safer for me, not riskier

The conventional warning about fasting is that you will lose muscle. For most people, that warning is correct. Muscle loss during a fast is driven by gluconeogenesis — the body breaking down amino acids to manufacture glucose — and gluconeogenesis is driven by the body’s belief that glucose is what it needs. A body with high baseline insulin, poorly trained at fat oxidation, with a brain that has never run smoothly on ketones, will reliably eat its own muscle to keep the glucose tap open. The fast becomes catabolic in the wrong direction.

A fat-adapted body does not have that fight. The brain is happy on ketones. The muscles are happy on fatty acids. There is no urgent demand for blood glucose, so there is no urgent reason to dismantle muscle to make some. Gluconeogenesis still happens at a slow trickle from glycerol and a small amount of amino acid — the body always needs some glucose for a few specific tissues — but it is not the runaway raid it becomes in a metabolically broken body.

Most people are not safe to fast hard, and the responsible advice for them is exactly what the dietitian says: do not. The path to safe fasting runs through metabolic flexibility first. You build the engine, then you turn it off for a while. Doing it in the other order is how people get hurt and conclude fasting does not work.

Two protocols

The fast itself does some of the work. The other half is what I do, or do not do, alongside it. I run two protocols depending on the day.

Protocol one: the full contrast stack

• Two days out: push the zone 2. Sixty to ninety minutes, easy nasal-breathing pace, drain the tank.
• One day out: lighter zone 2 or a normal lift, last meal is fattier than usual, plenty of salt.
• Day of: water, salt, electrolytes. Sauna in the morning. Cold plunge after. Long walk outside.
• Mid-fast: more sauna, more cold, more walking, more sleep. No hard training. The fast is the training.
• Break: start with a small portion of fatty meat. Do not break a fast on carbohydrates. Do not break a fast on a buffet. The first meal back is a probe, not a celebration.

This version is built around three mechanisms, all running on the same day.

The first is autophagy plus replacement. Fasting drives autophagy — the cellular cleanup process. Heat shock proteins from sauna also drive autophagy and protein quality control. Cold exposure drives mitochondrial biogenesis: the body actually building new mitochondria to replace the ones autophagy just chewed up. The interventions are not redundant. They are complementary. The fast empties the trash; the heat helps triage; the cold installs new hardware in the cleared space. This is the Contrast Boot doing double duty — it is already a great pre-workout primer, and it is also the cleanest way I know to amplify a fast.

The second is electrolytes. Fasting drops insulin, which tells the kidneys to dump sodium, which drags potassium and magnesium with it. The standard “fasting is hard” symptoms — headache, cramping, palpitations, anxiety, insomnia — are almost always electrolyte symptoms, not actual fasting symptoms. Sauna sweats them out faster, which sounds like a problem until you realize the answer is not to avoid sweating but to replace what you sweat. Salt the water. Magnesium at night. Potassium where it fits. The system rebalances. The “fasting feels brutal” complaint goes away.

The third is parasympathetic dominance. A fast is a low-grade stressor. A workout is a stressor. Modern life is a stressor. Stack too many stressors and the body goes into a sympathetic spiral — high cortisol, poor sleep, irritability, no benefit. Done right, this stack does the opposite. Long sauna sessions, cold plunges followed by quiet, walks outside without a phone, naps, deep sleep — all of it pulls the nervous system back down. The fast becomes a calming event instead of a stressful one. The body uses the energy it is not spending on digestion to repair itself, and it actually does the repair, because it is not also fighting a stress response.

The cost is time and access — sauna, cold plunge, most of a day. When I have those, this is what I run.

Protocol two: do absolutely nothing

Zone 2 the day before stays. That one piece of prep is cheap and it is the lever that most changes the biology of the fast — it drains the tank so the productive phase of the fast starts hours earlier. After that, nothing. I do not eat. I drink water with salt. I work, I read, I sit, I sleep when I am tired. No sauna. No plunge. The fast happens around whatever the day was already going to be.

What this version buys is the opposite axis. A cadence I will actually keep — a protocol I run twice a week beats one I run once a quarter. A real audit of metabolic flexibility, with no amplifiers masking the signal: either the body handles it cleanly or it does not. A genuine low-load day with no thermal stress and no cardio, which is what some weeks need more than another adaptation signal. The mental practice of sitting with hunger as information instead of emergency, which the stacked version lets you skip. And accessibility — no equipment, no membership, no plan.

The lazy fast still does the core work — insulin drops, ketones rise, autophagy fires, the gut gets a rest. Slower, without the multiplier. That is fine. Most of the benefit of fasting is fasting; the stack is the multiplier on top.

The window varies on either one — long overnight, full day, longer when the calendar permits and I want a deeper autophagy pass. The point is not the number on the clock. The point is what the body is set up to do with the time.

This isn’t a weight loss strategy. I still have weight to lose, and I am not running fasts to chase the scale. The point is mitochondrial health — the cellular cleanup, the replacement of broken hardware, the metabolic resilience, the discipline of remembering that hunger is information, not an emergency, and that a body in good order can go a long time between meals without drama. Weight loss happens or it does not, on the timeline the body decides. The fast is for the engine, not the number. If you are obese and metabolically broken, fasting still is not the lever — diet is. Fix the diet. Fix the engine. Then, and only then, turn the engine off for a while and let it cool.

This is also not medical advice. I am one data point. My wife, with MS, fasts in a different and gentler pattern than I do, calibrated to her body and her disease. The principle stays the same — be fat-adapted, prime the tank, stack recovery, replace electrolytes, do not break it on garbage — but the dose is hers, not mine, and the dose for you is yours, not mine. The point of writing this is not the protocol. The point is the framing: a fast done right is half fast and half recovery, and the recovery is where the body actually gets the benefit.

I work out hard. I rest harder. The fast is part of the rest.