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HOTISSN, Stronger By Science, Jeff NippardMarch 2026🌍 GLOBALHealth

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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.

Concept Fundamentals

2.8g/kg LM

Protein Target

ISSN rec

20%

Moderate Deficit

TDEE

~1 lb

Weekly Loss

500 cal def

Every 10 days

Refeed

Ready to run the numbers?

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.

TDEE and cutting calories with your chosen deficit levelProtein, carb, and fat grams for muscle-preserving fat loss

Sources:ISSNStronger By Science

Run the calculator when you are ready.

Calculate Your Cutting Phase MacrosEnter your stats to get TDEE, cutting calories, macro split, and body composition projection

Weight (lbs)Current body weight

Height (ft)Feet

Height (in)Inches

AgeYears

SexFor BMR calculation

Body Fat %Estimated or measured

Activity LevelFor TDEE multiplier

Training Days/WeekDays you lift

Deficit AggressivenessCalorie cut %

Training ExperienceAffects muscle retention

Target Weight Loss (lbs)Total lbs to lose

Cutting Duration (weeks)Cut length in weeks

cutting_phase_macros.shCALCULATED

TDEE

2743 cal

Cutting Calories

2195 cal

Deficit

548 cal

Protein

182g

Carbs

225g

Fat

63g

Training Day

2345 cal

Rest Day

2095 cal

Weekly Loss

1.1 lbs

Lean Mass

65.1 kg

Refeed

2743 cal / 10 days

Muscle Retention

75%

Est. End Body Fat

13.9%

📊 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.

2.8g/kg

Protein per Lean Mass

15-25%

Deficit Range

0.5-1%

Weekly Loss Target

7-14 days

Refeed Frequency

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?

✂️ 80-90% of weight lost on a well-designed cut comes from fat when protein is high and deficit is moderate

📊 The Mifflin-St Jeor equation is the most accurate BMR formula for the general population, used by dietitians worldwide

🏋️ Advanced lifters lose muscle more easily than beginners at the same deficit — experience increases protein needs

🔄 Jeff Nippard's 175→165 lb cut took ~12 weeks with a moderate deficit; he maintained strength throughout

📈 A 500-calorie daily deficit yields ~1 lb of fat loss per week (3500 cal = 1 lb fat)

🎯 Refeeds should prioritize carbs over fat — glycogen replenishment and leptin boost matter more than total calories

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

Prioritize protein distribution: 4-5 meals with 30-40g protein each supports muscle protein synthesis throughout the day.

Keep resistance training volume high — dropping sets accelerates muscle loss. Maintain intensity; reduce frequency only if needed.

Schedule refeeds on or near heavy training days to maximize glycogen replenishment and performance.

End cuts at 10-12% (men) or 18-22% (women) body fat for sustainable maintenance. Reverse diet by adding 100-150 cal/week to transition smoothly.

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

2.8g/kg

Protein per Lean Mass

20%

Moderate Deficit

~1 lb

Weekly Loss (500 cal def)

10-12%

End BF (Men)

Official Data Sources

International Society of Sports Nutrition ↗

ISSN position stands on protein, diets, and body composition

Stronger By Science ↗

Evidence-based nutrition and training articles

Jeff Nippard ↗

Science-based fitness and cutting protocols

Lyle McDonald ↗

Rapid fat loss handbook and diet research

⚠️ 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.