Macros Explained in 13 Minutes (Complete System)

People always ask me, what's the best diet for fat loss or what's the best diet for muscle gain? And what you have to understand is that the best diet is not following a diet at all.

The best diet is understanding how food moves through your body, what each macronutrient actually does once it gets there, and how your total energy output shifts in response to what you eat and how you move.

Before we go into any single piece of that, you need the whole map, because every part of it feeds the next part.

Food arrives carrying energy, and your body spends that energy in four different ways, none of which are fixed numbers since they change based on how much you eat and how much you move. The gap between what comes in and what goes out determines whether you gain or lose. Inside that gap, the three macronutrients decide what you gain or lose, whether it's muscle or fat, and whether you feel good doing it or feel like garbage the whole time.

That last part is what most people skip. They obsess over the gap and ignore what fills it.

One pound of body fat equals 3,500 calories. If you're in a 500 calorie deficit every day for a week, you'll lose about a pound. That math is real, but it only holds if the "out" side of the equation stays where you think it is, and it usually doesn't, which is the whole reason people stall out and think their metabolism is broken.

So let's build this from the ground up, starting with the three macros, because they determine everything about how your body responds to the deficit or surplus you put it in.

Protein first, because it does more jobs than the other two combined. One gram gives you four calories, and those calories come attached to amino acids that your body uses to build muscle tissue, enzymes, antibodies, and the structural proteins in your skin and organs.

When you don't eat enough protein, your body has two choices. It either stops building and repairing tissue, which means you feel weak and you recover slowly, or it breaks down your existing muscle to get the amino acids it needs for survival.

Your body doesn't have a protein storage tank. Fat gets stored in adipose tissue and carbs get stored as glycogen, but there's no reserve pool of free amino acids sitting around waiting to be used. The closest thing you have is your skeletal muscle, so that's what gets raided.

And the other thing that's important to know is that protein also has the highest thermic effect of any macronutrient, meaning your body burns 20 to 30% of protein calories by just digesting it.

So if you eat 200 grams of protein at four calories per gram, that's 800 calories. But your body burns 160 to 240 of those calories just processing it.

That's free caloric burn just from choosing the right foods.

The reason protein is so expensive to process comes down to what your body has to do with it. Carbs and fats can be stored more or less as they arrive, but amino acids have to be deaminated, meaning the nitrogen group gets stripped off, converted to urea in the liver, and shipped out through your kidneys. That process costs ATP, and ATP costs calories.

Fat, by comparison, sits somewhere around two to three percent thermic cost, and carbs land around five to ten percent. So swapping 100 calories of fat for 100 calories of protein changes your net absorbed energy by roughly 20 calories, every single time you do it.

Protein also keeps you full for longer than any other macro. It increases hormones like CCK and GLP-1 that actually tell your brain that you're full.

GLP-1 is the same pathway that the newer weight loss medications target, and the research on it goes back decades. Work published in the Annals of the New York Academy of Sciences in the late nineties examined how GLP-1 signaling suppresses appetite at the level of the brain, and protein happens to be the strongest natural stimulus for releasing it from cells in your small intestine.

CCK works on a shorter timeline, released within minutes of protein and fat hitting your duodenum, slowing how fast your stomach empties so food sits longer and you register fullness sooner.

That's why high protein diets keep showing up as more effective for fat loss study after study, and the deficit itself was never the magic ingredient since sticking with it long enough is what actually separates the people who succeed from the ones who quit.

Now carbohydrates, which also give you four calories per gram, and which get blamed for far more than they deserve.

The concern about carbs is not entirely made up. Refined carbs eaten in large amounts with no fiber, no protein, and no activity to absorb them will absolutely drive overconsumption and blood sugar swings, and that's a real observation people are reacting to. The correction is that carbohydrate as a category is not the cause of that, the context is.

Nearly all of your brain's fuel comes from glucose, and Dienel's review in Physiological Reviews lays out just how dependent that relationship is: your brain accounts for roughly 20 percent of your body's resting energy use despite being about 2 percent of your body weight, and almost all of that runs on glucose oxidation. Ketones can partially cover it during prolonged fasting or ketogenic adaptation, but the machinery is built around glucose.

Your muscles store carbs as glycogen, and this is where performance lives. Hearris and colleagues, writing in Nutrients in 2018, walked through how muscle glycogen regulates how hard you can train and how your muscle adapts to that training, with glycogen availability directly influencing the signaling pathways that drive adaptation.

Burke and van Loon's work in the Journal of Applied Physiology covered the resynthesis side, showing that muscle glycogen restoration after training depends heavily on carbohydrate intake in the hours that follow, with intakes around 1.2 grams per kilogram per hour maximizing the rate of refill.

Your thyroid needs carbs to produce T3, which is the hormone that controls your metabolic rate.

T4 is the storage form your thyroid releases, and it has to be converted to T3, the active form, mostly in your liver. That conversion is sensitive to energy availability and carbohydrate intake, and when both drop for long enough, conversion slows and reverse T3 rises, which is your body's way of turning down the thermostat when it thinks food is scarce.

The type of carbs matters, but not in a good-versus-bad way. Complex carbs with fiber slow absorption and keep you fuller for longer, while simple carbs without fiber spike your blood sugar and leave you hungry an hour later. A fast-digesting carb right after a hard training session is doing exactly what Burke's resynthesis data says it should, while that same carb eaten at 9pm on the couch is doing something else entirely.

Fats give you nine calories per gram, more than twice the other two, which makes them easy to over consume even when the source is olive oil or almonds or salmon.

But fats are the raw material for steroid hormone production. Cholesterol is the backbone molecule that testosterone, estrogen, and cortisol are all built from, and dietary fat is what supplies the substrate and the transport for that system.

Fats also carry vitamins A, D, E, and K, which are fat soluble, meaning they physically require dietary fat present in the same meal to be absorbed across your intestinal wall. Eat a salad with no fat and you absorb a fraction of the fat soluble vitamins in it.

And that's why it's important to understand that when you drop your fats too low, trying to cut calories, there's potential that you're gonna negatively impact your hormone production.

Fat is also the least filling macro per calorie, which is the trap. You can eat 400 calories of nut butter in about ninety seconds and feel roughly the same as you did before you started.

Once you understand the three macros, the output side of the equation is what determines whether the 3,500 calorie math actually holds up in the real world.

Your total daily energy expenditure, or TDEE, is four separate things stacked together.

First, you have your basal metabolic rate or your BMR. And that's just a fancy term that represents the calories you burn just existing. Heart beating, kidneys filtering, cells maintaining their membranes. For most people this is somewhere around 60 to 70 percent of the total.

Then you have your non-exercise activity thermogenesis, or NEAT, which is every bit of movement that isn't formal training. Walking to your car, standing at your desk, tapping your foot, carrying groceries.

Exercise activity thermogenesis makes up the third piece, and it's just the calories burned through actual workouts, lifting weights or going for a run. For most people this is the smallest slice, often five to ten percent of the total, which surprises people who assume their workout is where the calories go.

The fourth is the thermic effect of food. This is kind of what we talked about with protein earlier, which is basically the cost of digesting the foods that you consume, and it typically sits around 10 percent of total intake depending on how your macros are split.

The math falls apart once you've been in a deficit for a while, because your NEAT can quietly drop by 200 or 300 calories without you ever noticing it happening.

None of this is a conscious decision. It happens underneath your awareness entirely: you take the elevator without thinking about it, you sit down sooner, you stop pacing during phone calls, you fidget less. None of it registers consciously, and all of it comes out of your daily output.

So you set a 500 calorie deficit, your NEAT quietly drops 250, and now you're in a 250 calorie deficit while eating exactly what you planned. The scale slows, you assume you're doing something wrong, and you cut further, which drops NEAT further.

That's the loop most people are stuck in when they say their metabolism is broken.

Figuring out your starting point doesn't require getting lost in the technical details, and here's a simple way to do it.

For protein, your absolute minimum to prevent muscle loss is 0.7 to 0.8 grams per pound of lean body mass, which is different from total body weight entirely. A 200 pound person at 20 percent body fat has 160 pounds of lean mass, which puts the floor at about 128 grams per day.

The problem is that almost nobody knows their body fat percentage accurately, and calculating from a number you guessed at leaves no room for error. So I have people use one gram per pound of total body weight instead, which for a 200 pound person lands at exactly 200 grams. It's simple, it sits comfortably above the floor, and it doesn't require you to be right about your body composition.

For fats, the floor is 0.3 grams per pound of body weight, and dipping under that number is where hormone production starts to falter.

But again, I keep most people at 0.4 to 0.5 grams per pound because they feel better, they perform better, and they actually stick to the plan when they're not constantly fighting hunger. That 200 pound person lands between 80 and 100 grams of fat per day.

Carbs are the adjustable variable, and that's on purpose, since protein protects your muscle and fat protects your hormones while carbs fuel your performance and can move up or down as your training does.

Sedentary and trying to lose fat, start around half a gram per pound. Moderately active and maintaining, around one gram per pound. And if you're training hard and trying to build muscle, you might need as much as 1.5 to two grams per pound of carbs.

So that 200 pound person cutting starts at 100 grams, while maintaining sits at 200 grams, and if their focus is to build and grow, they're gonna eat as many as three to 400 grams of carbs per day.

What separates this from every calculator you've used comes down to one fact: every formula that estimates your BMR was built from population averages, and those population averages are only guesses about you, since you carry your own thyroid output, your own NEAT patterns, and your own history of dieting that no spreadsheet accounted for.

And so the way that I do it with my clients is we take those starting numbers and we eat them consistently for 14 days.

The number matters specifically because it's fourteen and not ten or seven, since water weight, sodium shifts, glycogen changes, and for women, the hormonal changes across a menstrual cycle that Oosthuyse and Bosch documented in Sports Medicine all move the scale in ways that have nothing to do with fat.

During those 14 days you weigh yourself daily at the same time each morning, you log calories and protein, and you write down your energy and training performance.

Then after that 14 days, you compare your average weight from week one to the average weight from the end of week two. What matters is the average and never the single day, since one morning's number just tells you about yesterday's sodium while a full week of mornings tells you something true about your energy balance.

Lost half a pound per week, you were in roughly a 250 calorie deficit. Gained half a pound, roughly a 250 calorie surplus. The math works backward cleanly because one pound equals 3,500 calories.

And so you just keep adjusting by 10% week after week until your weight stays stable within a pound or two over two weeks. That's your real maintenance, measured on your body, not estimated from a chart.

If you're losing weight too fast, more than two pounds per week, you probably should add 10% to your daily calories. Losing faster than that means you're pulling from muscle and driving the NEAT suppression that stalls you out later.

Not losing when you want to, subtract 10 percent. One change at a time, hold it two weeks, then evaluate again. Protein stays fixed, fat stays above its floor, carbs absorb the adjustment.

Test for 14 days, measure your average weight, adjust by 10% and repeat that until you find what works for your body.

Two things have to be in place or none of this holds. You need to be lifting two to three days a week minimum, because weight training is the signal that tells your body to keep muscle when it's short on energy, and without that signal the deficit takes muscle and fat together. And you need seven to nine hours of sleep, because that's when testosterone and growth hormone get released and tissue repair happens.

The reason every diet works for a while and then stops is that a diet gives you someone else's numbers and no way to update them. Your body changes what it spends the moment you change what you feed it, so a fixed set of numbers is always describing a version of you that no longer exists. The testing loop is the only part of this that keeps working after your body adapts, because adapting is exactly what it measures.

References:

Christophe J. Is there appetite after GLP-1 and PACAP? Ann N Y Acad Sci. 1998. https://pubmed.ncbi.nlm.nih.gov/9928026/

Dienel GA. Brain Glucose Metabolism: Integration of Energetics with Function. Physiol Rev. 2019. https://pubmed.ncbi.nlm.nih.gov/30565508/

Scott AJ, Mittal A, Meghdadi B et al.. Rewiring of cortical glucose metabolism fuels human brain cancer growth. Nature. 2025. https://pubmed.ncbi.nlm.nih.gov/40903569/

Hearris MA, Hammond KM, Fell JM et al.. Regulation of Muscle Glycogen Metabolism during Exercise: Implications for Endurance Performance and Training Adaptations. Nutrients. 2018. https://pubmed.ncbi.nlm.nih.gov/29498691/

Burke LM, van Loon LJC, Hawley JA. Postexercise muscle glycogen resynthesis in humans. J Appl Physiol (1985). 2017. https://pubmed.ncbi.nlm.nih.gov/27789774/

Oosthuyse T, Bosch AN. The effect of the menstrual cycle on exercise metabolism: implications for exercise performance in eumenorrhoeic women. Sports Med. 2010. https://pubmed.ncbi.nlm.nih.gov/20199120/