Macro Partitioning Logic
The order matters. Protein anchors, fat sets a floor, carbs fill what remains.
Protein 1.8-2.2 g/kg first. Fat 0.8-1.2 g/kg floor. Carbs fill the remaining kcal budget.
A calorie budget is the boundary; a macro split is the composition inside it. The evidence-based order: protein first (the only essential macro with demonstrated body-composition effect independent of calories), fat floor second (for hormonal and neurological function), carbs fill whatever remains. This sequence holds across cut, maintain, and bulk — only the calorie total changes.
Quick answer
Protein 1.8-2.2 g/kg first. Fat 0.8-1.2 g/kg floor. Carbs fill the remaining kcal budget.
Key points
- ▸ Protein: 1.8-2.2 g per kg bodyweight. 1.6 g/kg saturates muscle protein synthesis (Morton 2018 meta-analysis); 2.2 g/kg for aggressive cuts to preserve lean mass.
- ▸ Fat floor: 0.8-1.2 g per kg bodyweight. Below this, testosterone drops for men and menstrual function impairs for women. Above it, no further hormonal benefit.
- ▸ Carbs: fill the remaining kcal budget. Minimum for brain function ≈ 130 g/day; active populations need 3-6+ g/kg on training days.
- ▸ Calorie math: protein 4 kcal/g, carbs 4 kcal/g, fat 9 kcal/g. A 180 lb (82 kg) athlete at 2 g/kg protein = 164 g = 656 kcal.
- ▸ Protein target does not scale with calorie deficit. If anything it rises during a cut — more important to preserve muscle when energy is low.
- ▸ Fiber: target 14 g per 1000 kcal (IOM). Not a macro but affects satiety and health significantly.
Examples
- 180 lb (82 kg) athlete, maintain 2700 kcalProtein 164 g (656 kcal). Fat 82 g (738 kcal). Carbs 326 g (1306 kcal). 24%/27%/49% split.
- Same athlete, cut 2200 kcalProtein 180 g (720 kcal, raised to preserve muscle). Fat 66 g (594 kcal). Carbs 222 g (888 kcal). 33%/27%/40%.
- Same athlete, bulk 3100 kcalProtein 164 g (656 kcal). Fat 90 g (810 kcal). Carbs 409 g (1636 kcal). 21%/26%/53%. Extra kcal go to carbs for training fuel.
When to use which tool
- Fuel Partitioning · MacrosAfter computing TDEE and picking a cut/maintain/bulk target. Enter weight and let the tool compute grams per macro.Daily protein, fat, and carb targets anchored to bodyweight and training goal. Protein-first, fat floor second, carbs fill.
- Metabolic Floor · BMR / TDEEGet TDEE first so the macro split has a kcal anchor.Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure using Mifflin-St Jeor. Power-consumption view with cut / maintain / bulk zones.
Related
- Fuel Partitioning · MacrosDaily protein, fat, and carb targets anchored to bodyweight and training goal. Protein-first, fat floor second, carbs fill.
- Metabolic Floor · BMR / TDEECalculate your Basal Metabolic Rate and Total Daily Energy Expenditure using Mifflin-St Jeor. Power-consumption view with cut / maintain / bulk zones.
- Reading Your Macro TargetsHow to translate gram targets into actual food without weighing every bite.
- When Macro Targets Break DownKidney disease, extreme obesity, endurance athletes — the 1.8-2.2 g/kg rule does not always apply.
Frequently asked questions
› Do I need to hit exact macro grams daily?
No. Weekly averages matter more than daily. Hitting within ±10% of target is effectively equivalent to perfect adherence for body composition.
› Keto, high-carb, or standard split?
For body composition, all three work if protein is high and calories are controlled. Keto forces fat floor above 1.5 g/kg; high-carb drops fat toward the floor. Pick by adherence preference — the one you can hold.
› How should I use this guide with a Kefiw tool? How-to
Use the guide as the plan and the linked Kefiw tool as the check. Read the steps first, try the move manually, then use the tool to compare outputs, catch edge cases, and decide whether the result actually fits your task.
› What mistake do tool guides help avoid? Troubleshooting
Tool guides help avoid using a utility mechanically without understanding what you are trying to accomplish. Most word, writing, and text utilities are fast, but speed can hide context mistakes. Know whether you are solving a puzzle, cleaning copy, drafting a line, or checking a rule.
› Can a tool guide help me learn the skill? How-to
A tool guide can help you learn if you pause before accepting the output and ask why it worked. Compare your first guess with the tool result, look for the rule or pattern, and repeat that review. Passive copying solves one task; active review builds the skill.