Formula, in Fat Loss
Macro Cycling Formula
Macro cycling matches daily carbohydrate intake to daily training demand. Hard training days get higher carbs (6-10 g/kg); easy or rest days get fewer (3-4 g/kg). Protein stays constant at 1.6-2.2 g/kg every day. Fat fills the remainder. Burke & Hawley 2018 framework reflects glycogen recovery research — chronic over-feeding carbs on rest days adds calories without benefit; under-feeding carbs on training days impairs session quality.
4 variables. Published May 14, 2026. By AI Fit Hub.
carb_g_training = mass_kg × (6 to 10) g/kg
carb_g_rest = mass_kg × (3 to 4) g/kg
protein_g = mass_kg × (1.6 to 2.2) g/kg [constant across days]
fat_g = remaining calories / 9 [fat is the slack] Variables
carb_g_training
Training-day carbs
Higher dose to fuel session glycogen needs + replace post-session loss. Range: 6 g/kg (moderate training) to 10 g/kg (multi-hour endurance days).
carb_g_rest
Rest-day carbs
Lower dose since metabolic demand is lower. Range: 3 g/kg (sedentary rest) to 4 g/kg (active recovery — walking, mobility work, easy spin).
protein_g
Protein (constant)
ISSN 2017 evidence-based range: 1.6-2.2 g/kg/day. Higher end (2.0-2.2) during fat-loss phases or for strength athletes; 1.6 for general fitness. Keep CONSTANT across training and rest days — protein protects against muscle loss most effectively when daily.
fat_g
Fat (remainder)
After protein + carbs, fat fills the remaining calories. Floor at 0.8 g/kg for hormone health (testosterone, ghrelin/leptin signaling). On hard-training days fat tends to be lower; on rest days higher.
Step by step
- 1
Identify your training schedule. Categorize each day: hard training, moderate, easy/rest.
Week: Mon hard lift, Tue easy run, Wed hard lift, Thu rest, Fri hard lift, Sat moderate cardio, Sun rest. So 3 hard days, 1 moderate, 1 easy, 2 rest.
- 2
Set protein target. Same every day.
80 kg × 2.0 g/kg = 160 g protein/day (every day).
- 3
Set hard-day carb target: 6-10 g/kg based on duration/intensity.
Hard lift (60-90 min): 6 g/kg → 80 × 6 = 480 g carbs.
- 4
Set rest-day carb target: 3-4 g/kg.
Full rest: 3 g/kg → 80 × 3 = 240 g carbs. Easy run day: 4 g/kg = 320 g.
- 5
Fill remaining calories with fat. Compute total calories per day type from TDEE.
Hard lift day: 160 × 4 + 480 × 4 = 640 + 1,920 = 2,560 from P+C. TDEE 2,800. Remaining: 240 cal → 27 g fat. Rest day: 160 × 4 + 240 × 4 = 1,600 from P+C. TDEE 2,300 (no exercise). Remaining: 700 cal → 78 g fat. Compare: hard-day low fat + carb-loaded; rest-day higher fat.
Worked example
80 kg recreational lifter, 3 hard sessions/week + 1 moderate + 1 easy + 2 rest, maintenance kcal cycle
Body mass
80 kg
TDEE hard day
2,800 kcal
TDEE rest day
2,300 kcal
Protein constant
2.0 g/kg = 160 g/day
Hard day: 160P / 480C / 27F (kcal 640+1920+243 = 2,803) Mod day (4 g/kg C): 160P / 320C / 47F (kcal 640+1280+423 = 2,343) Rest day: 160P / 240C / 78F (kcal 640+960+700 = 2,300) Weekly avg: (3×2,803 + 1×2,500 + 1×2,343 + 2×2,300) / 7 = 2,535 kcal/day
Weekly average maintenance with daily variance. Total weekly carbs: 3,200 g (vs 4,200 g if 480 carbs every day). Saved ~1,000 g carbs/week = ~4,000 fewer kcal across the week. Allows a slight surplus on hard days (supporting recovery + training quality) without exceeding weekly maintenance.
Common variations
Run the numbers next
- Nutrition Macro Calculator
Convert calorie targets into protein, carbs, and fat grams for your goal.
- Nutrition TDEE Calculator
Estimate your daily energy expenditure with Mifflin-St Jeor + activity factors.
- Nutrition Protein Intake Calculator
Get daily protein targets based on training level and goal.
Questions people ask next
What is macro cycling and how does it work?
Macro cycling matches daily carbohydrate intake to daily training demand: hard training days get higher carbs (6-10 g/kg) and easy or rest days get fewer (3-4 g/kg). Protein stays constant at 1.6-2.2 g/kg every day and fat fills the remaining calories. It avoids over-feeding carbs on rest days while still fueling hard sessions.
How many carbs on a rest day versus a training day?
Training days use 6 g/kg for moderate work up to 10 g/kg for multi-hour endurance days, while rest days drop to 3 g/kg for sedentary rest or 4 g/kg for active recovery like walking or an easy spin. For an 80 kg lifter that is about 480 g of carbs on a hard day versus 240 g on a full rest day.
Should protein change on training versus rest days?
No. Protein stays constant at 1.6-2.2 g/kg every day, with the higher end (2.0-2.2) during fat-loss phases or for strength athletes. Daily protein protects against muscle loss most effectively, so it does not get cycled the way carbs do.
Does macro cycling save calories over the week?
Yes, by lowering carbs on easy and rest days. The worked example for an 80 kg lifter totals about 3,200 g of carbs per week versus 4,200 g if you ate 480 g every day, roughly 1,000 g fewer carbs or about 4,000 fewer calories across the week, while still allowing a slight surplus on hard days.
Does carb timing or back-loading matter for macro cycling?
Not much. Carb back-loading (concentrating most daily carbs post-training) is not well supported empirically; total daily carbohydrate matters more than timing for most outcomes. The cycling benefit comes from matching the day's total carbs to that day's training demand, not from when you eat them.
Sources
- Burke et al. (2018). Toward a common understanding of diet-exercise strategies to manipulate fuel availability for training and competition preparation in endurance sport. , International Journal of Sport Nutrition and Exercise Metabolism — periodized nutrition framework
- Burke (2015). Re-examining high-fat diets for sports performance: did we call the 'nail in the coffin' too soon? , Sports Medicine — train-low protocol evidence
- Byrne et al. (2018). Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. , International Journal of Obesity — diet break / refeed evidence
- Aragon & Schoenfeld (2013). Nutrient timing revisited: is there a post-exercise anabolic window? , JISSN — timing vs total daily intake