I spent my entire adult life looking for the right diet. The Zone came first. I was single, had free time, was excited about coaching, and weighed and measured everything. It worked. Then life set in: kids, no sleep, and the kitchen scale stopped being a tool and started being an accusation. Next came Paleo, with simpler rules and less friction. It did not make things worse, but nothing really improved either. More years passed with more stress, less training, more sitting, and more eating. Then came Keto. I lost weight, until I didn’t. And somewhere in that last failure, the frustration stopped feeling like a problem to solve and started feeling like something closer to hopeless.
Nutrition is hard because it isn’t a single-variable equation. Training has complexity, but the scoreboard is clean: load, distance, time. Nutrition enters a living system that changes hour to hour with sleep, stress, hormones, training load, age, and lean mass. The same meal can be fuel for one athlete and a problem for another. That’s not a character issue. It’s physiology.
Successful training is built on a simple reality: outcomes aren’t random. They’re downstream of what you eat and how you work out. So this series is about inputs and outcomes: change what you can control, and measure what matters, because the body keeps score. Before we talk about “more work,” we have to talk about the fuel and hormones that decide whether work becomes adaptation or just fatigue.
Coaches have seen it on the gym floor: two athletes take the same stimulus and one thrives while the other unravels. Sometimes that looks like a fitness problem, but it is really a fuel-handling problem. The unraveling athlete is eating in a way that creates more glucose demand, more insulin demand, more hunger, and more recovery cost than their system can currently manage well. The issue is not simply that the athlete is unfit. It is that the total input and the body’s ability to process that input are out of proportion.
That is the honest conversation. Not good versus bad, but how this body responds to what it is eating. The same meal can support one athlete and destabilize another, because tolerance, stress load, and recovery capacity are not the same.
Call it the ability to regulate energy: the capacity to take in fuel, mount an appropriate hormonal response, use that fuel, and return to baseline. Not “never spike.” Not “never eat carbs.” Healthy systems respond appropriately, clear the job, and settle back down. Fuel comes in, the right signal shows up, the workout gets done, and the athlete settles back into normal: steady energy, calm appetite, ready to train tomorrow.
That is the practical coaching lens. We are not asking whether carbs, fat, or protein are good in the abstract. We are asking whether this athlete, with this training load, this body composition, this sleep, and this stress, can process their current intake without unstable energy, excess hunger, poor sleep, or stalled recovery. Once you ask it that way, the conversation gets simpler and more honest.
So the question that matters isn’t “Which diet wins?” It’s this: can this athlete handle their current macro mix and timing without paying for it with unstable energy, loud hunger, poor sleep, or stalled recovery? That is macronutrient tolerance. It’s not identity. It’s metabolic capacity: the ability to handle a given fuel load, mount the right hormonal response, and return to baseline in a reasonable time. And that capacity can be trained. But it has to be measured first.
Markers: The Metabolic Scoreboard
No single set of markers is sacred. Any measure that reliably reflects energy regulation and can be repeated over time will do. The three below are where we often start, not because they’re the only options, but because they’re accessible, coachable, and cross-validating. Swap or add markers when they better match the athlete and the question. The method stays the same: establish a baseline, change the inputs, re-test, watch the fingerprint move.
HbA1c. The rolling average of glucose exposure over roughly three months. It tells you whether the athlete is living in a high-glucose environment or keeping the system clean between meals. When this number drifts upward, the inputs have been louder than the body can handle for a while.
Fasting insulin. How hard the body is working to keep glucose in range. Two athletes can have the same blood sugar, while one is barely trying and the other is flooding the system with insulin to hold the line. This is the hidden cost, the marker that tells you the system is compensating before anything else breaks.
TG/HDL. A window into how the body is trafficking fuel. When triglycerides climb and HDL drops, the system is overloaded, with too much fuel circulating and not enough being cleared or used well. When the ratio tightens, fuel is moving where it should and storage pressure is coming down.
Macros: The Adjustable Inputs
Macronutrients are not just calories. They are inputs that reliably shape what happens next. When macros enter the body, they produce predictable hormonal responses that influence whether fuel is used, stored, or continues to circulate. Predictable is not the same as identical. The direction is reliable, but the magnitude depends on the athlete. Insulin is the central signal: not a villain, but the traffic cop for fuel. When the signal is appropriate and short-lived, athletes feel steady. When it’s excessive, or constantly required, athletes get needy: hungry, reactive, and dependent on frequent intake to feel normal.
Macronutrient tolerance changes when the hormonal bill changes. Adjust carbs, protein, and fat, and you change the size and duration of the hormonal response after meals. Do that consistently and the athlete gets more time at baseline, better clearance, and a more predictable response.
Not all macros deserve equal priority. Proteins and fats contain essentials, nutrients the body needs but cannot produce on its own. Carbohydrates do not. So we anchor protein first, then use fat and carbohydrate to shape the fuel environment, and adjust carbohydrate most aggressively based on tolerance.
Protein is the stability lever, and the insurance policy. When protein comes up to an adequate level, appetite gets quieter and the athlete stops acting like every missed snack is an emergency. Protein produces a more controlled, stabilizing response than a big carb hit alone, especially when it replaces some carbs or prevents grazing. When protein is inadequate, the body has two options: drive appetite harder in order to consume more, or pull amino acids from lean tissue over time. Either way, recovery suffers and capacity erodes, making the athlete less tolerant of the same carbs they used to handle.
The Coaching Move set a protein floor first, then adjust carbs and fat around that foundation.
Fat is context-dependent: steady fuel or easy storage. When fat replaces carbs, insulin demand typically drops, with fewer blood sugar spikes and smoother energy, because you’ve reduced the glucose management problem. But fat stacked on top of frequent high-insulin meals is the easiest macro to park, because the traffic cop is already waving fuel into storage. Increasing fat helps when it lowers the insulin load by displacing carbs or tightening timing. Decreasing fat helps when it reduces total intake, but if the replacement is mostly carbs and meal frequency stays high, the insulin signal stays elevated and the athlete stays locked in snack-dependence.
The Coaching Move don’t argue fat versus carbs. Coach the signal. Reduce the insulin burden, create baseline time, and choose the mix that produces calm appetite and predictable energy.
Carbs are the insulin dial. Lower carbs, or lower the carb dose per meal, and you usually get a smaller glucose rise and a smaller insulin response. Less traffic control required. That creates space for insulin to come back down between meals, which is where stability lives. Then training does its job by changing the place that fuel has to go. This is how carb tolerance is built. Start with a dose the athlete can clear, place carbs where demand exists, and expand only when the response is predictable.
The Coaching Move find the carb dose the athlete can clear with a stable response, keep it lower on sedentary days, and recognize that higher-activity days may tolerate more because fuel use and clearance are higher. Expand only when energy, appetite, and recovery stay predictable.
What we can help athletes understand is that the macro mix sends a signal, and the amount and frequency of that signal have to match the life being lived. Protein has to be anchored because appetite, recovery, and lean tissue depend on it. Fat can be steady fuel, but it still has to fit the whole pattern. Carbohydrate has to match demand and tolerance, not habit or ideology. That is the skill: finding the mix and rhythm that let the athlete eat, train, recover, and return to baseline without constant hunger, unstable energy, or stalled progress.
Squeeze the Sponge
Think of muscle as a sponge. Every time you eat carbs, the body has to put that glucose somewhere, and muscle is one of the biggest places it can go. But here is what most people miss: glycogen is not just fuel in reserve. It is also one of the body’s ways of pulling glucose out of circulation and storing it somewhere safe. The sponge exists to absorb the excess so glucose doesn’t build up in circulation.
Now picture an athlete who eats a high-carb diet and does not train much. The sponge is already wet. There is less room. Insulin stays elevated longer, trying to move more glucose into tissue that doesn’t have room for it. Less fuel gets burned, more gets pushed toward storage, and the athlete pays for it with worse energy, more hunger, and poorer recovery. That is not a willpower problem. That is a saturated system.
Now picture the athlete who trains hard. Training squeezes the sponge. Every rep, every interval, every heavy set pulls glycogen out and creates room for the next meal’s glucose to be absorbed. The athlete who trains hard has a drier sponge. Insulin does its job, clears the fuel, and comes back down. The athlete who sits all day and eats the same carbs has a wetter sponge. Insulin has to work louder and longer, and the system is slower to return to baseline.
This is why nutrition coaching cannot be separated from training. Strength and conditioning are not just about performance. They are part of metabolic capacity. We are not just changing food. We are upgrading the system that has to handle it.
The Coaching Move treat nutrition like training. Define inputs, track response, adjust, and re-test. Stop guessing. Stop selling ideology. Run an experiment on the athlete’s biology, and judge the plan the same way you judge a program: by outcomes you can observe and repeat.
The Path Forward
The goal isn’t to put everyone on the same plan. It’s to build a system that allows each person to handle life, different foods, different days, different stress levels, without constant volatility. That requires humility, measurement, and a willingness to adjust based on biology, instead of forcing biology to fit a template.
For years, performance was the scoreboard: task completion, skill, strength, stamina. Keep that scoreboard. But it isn’t enough. Add a metabolic scoreboard: simple, repeatable markers that show whether the athlete is handling fuel well or paying for the plan under the surface.
The body doesn’t care what you believe about food. It responds to what you actually eat. The diet wars are a distraction. Zone, Keto, Paleo, Carnivore: none of them are the point. The point is what the food signals and what the body does with it. Calories in, calories out is incomplete. The body is not a passive container. Food is material and signal. The body builds with it, responds to it, and records the answer in markers you can read.
Your internet guru does not get a vote. The labs do.
Part 1 ends on the metabolic scoreboard: how the body processes fuel. Part 2 picks up the other half of energy regulation: whether the body can take a stress hit and return to baseline.