Cutting Phase Science: Lose Fat, Keep Your Muscle
Cutting phase (fat loss while preserving muscle) requires a precise calorie deficit with HIGH protein — 2.3-3.1g per kg of lean mass, the highest of any training phase. Jeff Nippard's documented cut from 175 to 165 lbs with exact macro tracking exemplifies the approach: moderate 20% deficit, calorie cycling for training vs rest days, and planned refeeds. This calculator helps you design a science-backed cutting plan with protein targets, training/rest day splits, and body composition projections.
About This Calculator: Cutting Phase Macro
Why: Cutting requires the highest protein intake of any phase to preserve muscle. A moderate deficit with calorie cycling and refeeds optimizes fat loss while maintaining strength and lean mass. This calculator applies evidence-based targets to your stats.
How: Enter your weight, height, age, sex, body fat %, activity level, training days, deficit aggressiveness, experience, target weight loss, and cutting duration. The calculator uses Mifflin-St Jeor for BMR, applies your deficit, and allocates macros at 2.8g/kg lean mass protein, 0.8g/kg fat, with carbs filling the rest. Training days get +150 cal, rest days -100 cal.
📋 Quick Examples — Click to Load
📊 Macro Split (Protein / Carbs / Fat)
Daily macro targets in grams
📈 Weight Trajectory Over Cutting Duration
Projected weight at key weeks
📊 Training vs Rest Day Calories
Calorie cycling: +150 training, -100 rest
📈 Body Composition Projection
Lean mass preserved vs fat lost over cut duration
⚠️For educational and informational purposes only. Verify with a qualified professional.
Cutting phase nutrition requires a precise calorie deficit with high protein (2.3-3.1g/kg lean mass) to preserve muscle while losing fat. Jeff Nippard's documented cut from 175 to 165 lbs exemplifies this approach: moderate 20% deficit, 2.8g/kg lean mass protein, and calorie cycling (training days +150 cal, rest days -100 cal). The International Society of Sports Nutrition recommends refeeds every 7-14 days at maintenance to support leptin and adherence. This calculator helps you design a science-backed cutting plan.
Sources: ISSN, Stronger By Science, Jeff Nippard.
Key Takeaways
- • Protein at 2.8g/kg lean mass is the single most important factor for muscle preservation during a cut — higher than bulking or maintenance
- • A 15-25% calorie deficit balances fat loss speed with muscle retention; aggressive deficits increase catabolism risk
- • Calorie cycling (more on training days, less on rest days) supports performance and adherence without slowing fat loss
- • Refeed days at maintenance every 7-14 days replenish glycogen, boost leptin, and improve long-term adherence to the cut
Did You Know?
How Does Cutting Phase Macro Calculation Work?
BMR and TDEE (Mifflin-St Jeor)
Basal metabolic rate is estimated using the Mifflin-St Jeor equation: BMR = 10×weight(kg) + 6.25×height(cm) - 5×age + 5 (men) or -161 (women). TDEE = BMR × activity multiplier (1.2 sedentary to 1.9 very active). This gives your maintenance calories.
Deficit and Cutting Calories
Conservative (15%), moderate (20%), or aggressive (25%) deficit is applied. Cutting calories = TDEE × (1 - deficit%). A 20% deficit on 2500 TDEE = 2000 cutting calories. Weekly loss ≈ deficit × 7 ÷ 3500 lbs.
Macro Allocation
Protein: 2.8g/kg lean mass (lean mass = weight × (1 - body fat %)). Fat: 0.8g/kg body weight for hormone health. Carbs: remaining calories after protein (4 cal/g) and fat (9 cal/g). Training days get +150 cal from carbs; rest days -100 cal.
Expert Tips
Cutting Approach Comparison by Deficit Level
| Deficit Level | Calorie Cut % | Refeed Frequency | Best For |
|---|---|---|---|
| Conservative | 15% | Every 14 days | Beginners, long cuts |
| Moderate | 20% | Every 10 days | Most intermediates |
| Aggressive | 25% | Every 7 days | Contest prep, short cuts |
Frequently Asked Questions
How much deficit for cutting?
Research recommends a 15-25% calorie deficit for sustainable fat loss. Conservative (15%) preserves more muscle and suits beginners. Moderate (20%) is ideal for most intermediates. Aggressive (25%) speeds fat loss but increases muscle loss risk. Jeff Nippard's cut from 175 to 165 lbs used a moderate deficit with high protein (2.8g/kg lean mass) to preserve muscle.
How much protein during a cut?
The International Society of Sports Nutrition recommends 2.3-3.1g per kg of lean body mass during a deficit to maximize muscle retention. Lean mass = weight × (1 - body fat %). A 175 lb male at 18% body fat has ~65 kg lean mass, so 182-202g protein daily. Higher protein intake during cutting reduces muscle catabolism and preserves strength.
How fast should I lose weight?
Aim for 0.5-1% of body weight per week. For a 175 lb person, that's 0.9-1.75 lbs/week. Faster loss increases muscle loss. A 500-calorie daily deficit yields ~1 lb/week. Stronger By Science recommends staying under 1% weekly for intermediates to preserve lean mass.
What are refeeds?
Refeed days are planned higher-calorie days (usually at maintenance) every 7-14 days. They replenish glycogen, boost leptin, and improve adherence. Moderate cuts: refeed every 10 days. Aggressive cuts: every 7 days. Conservative cuts: every 14 days. Refeeds should come from carbs, not fat.
How to prevent muscle loss?
Prioritize high protein (2.8g/kg lean mass), use a moderate deficit (15-20%), maintain resistance training volume, and avoid aggressive cuts. Training experience matters: beginners retain more muscle than advanced lifters at the same deficit. Calorie cycling (more on training days, less on rest days) helps preserve performance.
When to end a cut?
End when you reach your target body fat or after 12-16 weeks. Men typically stop at 10-12%, women at 18-22% for sustainable maintenance. Signs to stop: performance drops, excessive fatigue, or reaching a healthy body fat range. Reverse diet by adding 100-150 cal/week to transition back to maintenance.
Key Statistics
Official Data Sources
⚠️ Disclaimer: This calculator provides estimates for educational purposes. Individual needs vary based on metabolism, training, and health status. Consult a healthcare provider or registered dietitian before starting a cutting phase, especially if you have a history of eating disorders or medical conditions. This is not medical or nutritional advice.