Macro Split Guide
Why macro planning anchors on protein first, fat floor second, carbs last.
Protein anchored at 1.6-2.2 g/kg, fat floor at 20-30% of kcal, carbs backfill whatever kcal budget remains.
Macro planning fails when it starts from equal thirds or arbitrary ratios. The evidence-based approach anchors on protein — the only macro with demonstrated body-composition effects independent of kcal — then sets a fat floor for hormonal and vitamin-absorption function, and finally backfills carbs to reach the kcal target. This order reflects physiological necessity: protein is the highest-priority nutrient, fat is essential, carbs are discretionary energy.
Part of: Bio-Chemical Logistics
Quick answer
Protein anchored at 1.6-2.2 g/kg, fat floor at 20-30% of kcal, carbs backfill whatever kcal budget remains.
Key points
- ▸ Protein anchor: 1.6-2.2 g/kg bodyweight by training state. Morton 2018 meta-analysis shows 1.6 g/kg saturates MPS; higher doses are neutral, safe to 3.5 g/kg for renal-healthy adults.
- ▸ Fat floor: 0.8-1.2 g/kg or 20-30% of kcal. Below 20% of kcal, testosterone and estradiol decline within weeks; fat-soluble vitamin absorption (A, D, E, K) also drops.
- ▸ Carb backfill: whatever kcal remain after protein and fat are allocated. Carbs are not strictly essential — humans synthesise glucose from protein — but they are the cheapest training fuel.
- ▸ Protein kcal density is 4 kcal/g; carbs 4 kcal/g; fat 9 kcal/g. An 82 kg lifter at 2.0 g/kg protein = 164 g = 656 kcal before any other macro.
- ▸ Cut / maintain / bulk shift the kcal target; macros adjust proportionally but protein stays pinned at g/kg — never dropping below 1.6 g/kg even in a deep deficit.
- ▸ Fibre, micronutrients, and meal timing sit outside the macro split but matter; macros are the skeleton, not the whole diet.
How to
- Compute TDEE with a metabolic-floor calculator; adjust ±300-500 kcal for cut or bulk.
- Set protein in grams: bodyweight_kg × 1.6-2.2 depending on training state and deficit depth.
- Set fat in grams: bodyweight_kg × 0.8-1.2, or 25% of kcal target — whichever is higher.
- Compute remaining kcal: kcal_target − (protein_g × 4) − (fat_g × 9). Divide by 4 for carb grams.
- If carb grams go negative, kcal target is too low for the protein+fat floors — raise kcal or accept a lower protein target for the cut phase.
Examples
- 82 kg (180 lb) · maintain · 2700 kcalProtein 147 g (1.8 g/kg · 588 kcal) · fat 82 g (1.0 g/kg · 738 kcal) · carbs 343 g (1372 kcal / 4). 27/27/46 split.
- 70 kg · cut · 1900 kcalProtein 154 g (2.2 g/kg · 616 kcal) · fat 56 g (0.8 g/kg · 504 kcal) · carbs 195 g (780 kcal / 4). Protein held high to preserve muscle through deficit.
- 90 kg · bulk · 3400 kcalProtein 162 g (1.8 g/kg · 648 kcal) · fat 108 g (1.2 g/kg · 972 kcal) · carbs 445 g (1780 kcal / 4). Carb ceiling supports training volume.
When to use which tool
- Fuel Partitioning · MacrosPlanning or adjusting a diet phase — any cut, maintain, or bulk block benefits from explicit macro targets.Daily protein, fat, and carb targets anchored to bodyweight and training goal. Protein-first, fat floor second, carbs fill.
- Anabolic Trigger · MPS BolusCheck per-meal bolus maths against daily protein floor; the total must match the meal frequency.Per-meal protein bolus that maximises muscle protein synthesis. 0.25-0.40 g/kg per feeding, 1.6-2.2 g/kg daily.
- CYAN · STABLE — Protein ≥ 1.8 g/kg, fat ≥ 0.8 g/kg — physiological floors cleared; performance and endocrine function supported.
- GOLD · GUARDED — Protein 1.6-1.8 g/kg, fat 20-25% kcal — adequate for general health and recreational training; most Western diets sit here on paper but often miss protein.
- MAGENTA · CRITICAL — Protein under 1.2 g/kg or fat under 20% kcal — muscle loss accelerates in deficit; hormonal panel shifts within weeks.
Related
- Fuel Partitioning · MacrosDaily protein, fat, and carb targets anchored to bodyweight and training goal. Protein-first, fat floor second, carbs fill.
- Anabolic Trigger · MPS BolusPer-meal protein bolus that maximises muscle protein synthesis. 0.25-0.40 g/kg per feeding, 1.6-2.2 g/kg daily.
- 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.
- Bio-FuelRank food by kilocalories per dollar and convert grocery spend into days of biological uptime at a 2,000 kcal baseline.
- The MPS Protein ThresholdWhy 0.25-0.40 grams per kilogram per meal is the anabolic trigger.
- Interpreting Your Protein TargetsWhey, eggs, beef, and plant protein — not all 30g boluses are equal.
- Protein Bolus Edge CasesOlder lifters, intermittent fasters, vegans, and very heavy athletes.
Frequently asked questions
› Why protein first instead of carbs? Troubleshooting
Protein is the only macro with demonstrated body-composition effects at a given kcal intake. Under-eat protein and you lose muscle in a deficit or fail to gain it in a surplus. Fat and carbs are interchangeable on a kcal-for-kcal basis within their floors.
› Is 2 g/kg too much protein? Trust & accuracy
No. Morton 2018 meta-analysis landed the MPS saturation point at 1.6 g/kg. Higher intakes are metabolically neutral for renal-healthy adults, with upper-bound safety supported to 3.5 g/kg. The "too much protein harms kidneys" story does not replicate outside of pre-existing kidney disease.
› Do I need to weigh food?
For the first 2-4 weeks of a structured phase, yes — calibrated eyeballing is hard without a reference. After a month of scale-tracking, visual estimation becomes reliable within ±10%. Most people chronically under-estimate fat and over-estimate protein by 20-40% when not weighing.
› 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.