Fasting Weight Loss Calculator
Estimate projected weight change from an intermittent-fasting calorie pattern using adaptive energy-balance math.
Faster but often manageable with adequate protein and recovery.
Activity selection: Lightly Active. Light exercise 1-3 days/week.
Projected Weekly Loss Pace
Interpretation is based on projected percent body-weight change per week in your fasting setup.
| RANGE | CATEGORY |
|---|---|
| -1-0 | Weight Gain Average energy intake appears above expenditure in this setup. |
| 0-0.25 | Very Slow Low weekly rate. Useful for maintenance-adjacent phases or conservative starts. |
| 0.25-0.75 | Steady Typical sustainable pace for many adults. |
| 0.75-1 | Brisk Faster but often manageable with adequate protein and recovery. |
| 1-1.50 | Aggressive Aggressive pace. Monitor performance, hunger, and sleep quality closely. |
| 1.50-2 | Very Aggressive High weekly rate with increased lean-mass retention risk. |
| 2+ | Extreme Very high projected pace. Medical supervision is recommended. |
How This Fasting Calculator Works
The model estimates daily energy expenditure from Mifflin-St Jeor BMR and activity level, then simulates day-by-day weight change across fasting and non-fasting intake days.
Unlike a single static deficit formula, this projection recalculates expenditure as body weight changes, which reduces overestimation over longer timelines.
Practical Use
Use this as a planning tool, not a guarantee. Real outcomes are influenced by adherence, spontaneous intake changes, sleep, stress, medications, and fluid shifts.
For non-fasting calorie setup, estimate maintenance with the TDEE Calculator or the Calorie Calculator, and set a target with the Calorie Deficit Calculator. For meal-level intake estimates from food photos, use the Calorie Scanner. For step-based walking output, add the Steps to Calories Calculator.
If you want a quick protocol comparison (16:8, 18:6, OMAD, or 5:2), use the Intermittent Fasting Calculator.
If you prefer a non-fasting setup based on one daily calorie target, use the standard daily-intake timeline model.
To summarize progress after a phase, calculate net percentage change with the start-to-current percentage tracker.
References
- NIDDK overview of adult overweight and obesity management:NIDDK Adult Overweight and Obesity
- Mifflin-St Jeor resting metabolic rate equation (PubMed):A New Predictive Equation for Resting Energy Expenditure
- Time-restricted eating trial in adults with overweight/obesity (JAMA Internal Medicine):Effect of Time-Restricted Eating on Weight Loss
More Calorie Tools →
Intermittent Fasting Calculator
Estimate fasting-protocol calorie intake, daily expenditure, and weekly pace.
TDEE Calculator
Estimate total daily energy expenditure from BMR equation and activity level.
BMR Calculator
Estimate basal metabolic rate from standard resting-energy equations.
Calorie Deficit Calculator
Calculate deficit targets and daily calories from your selected weekly pace.