Your Information
Your Weight Loss Journey
Enter your information and click Calculate to see your weight loss timeline
Time to Goal
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Daily Calories Needed
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Target Daily Intake
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Use ToolThe Science Behind Weight Loss
How Weight Loss Works
Weight loss occurs when you consistently consume fewer calories than your body uses. This creates a calorie deficit, forcing your body to use stored energy (primarily fat) to make up the difference.
Basic Principles
- 3,500 calories equals approximately 1 pound (0.45 kg) of fat
- To lose 1 pound per week, you need a deficit of 500 calories per day
- Safe weight loss rate is 1-2 pounds (0.5-1 kg) per week for most individuals
- Rapid weight loss can lead to muscle loss, nutritional deficiencies, and other health issues
Weight Loss Formulas
Basal Metabolic Rate (BMR)
The amount of energy your body needs to maintain basic functions at rest.
Harris-Benedict Equations (Revised):
For men: BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age)
For women: BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age)
Total Daily Energy Expenditure (TDEE)
Your total calorie expenditure per day, factoring in activity level.
TDEE = BMR × Activity Factor
Weight Loss Calculation
Estimated time to reach goal weight based on calorie deficit:
Days = (Current weight - Goal weight) × 7700 / Daily calorie deficit
Note: 7700 calories ≈ 1 kg of body fat
Factors Affecting Weight Loss
Metabolic Adaptation
As you lose weight, your body requires fewer calories to function. This can lead to plateaus where weight loss slows or stops entirely. Our calculator accounts for this by recalculating your energy needs as your weight decreases.
Body Composition Changes
Weight loss includes both fat and lean tissue (including muscle). The ratio varies based on diet, exercise, initial body composition, and genetics. Resistance training helps preserve muscle mass during weight loss.
Water Weight Fluctuations
Day-to-day weight fluctuations are normal and often due to water retention, food in your digestive system, and glycogen storage. This is why weekly trends are more important than daily weights.
Tips for Healthy Weight Loss
- Focus on nutrient-dense foods to maintain health while in a calorie deficit
- Include protein in each meal to help preserve muscle mass
- Stay hydrated, as thirst can sometimes be mistaken for hunger
- Incorporate strength training to maintain muscle mass
- Get adequate sleep, as poor sleep can affect hunger hormones
- Consider a smaller deficit (250-500 calories) for more sustainable weight loss
- Regular exercise improves metabolic health and helps maintain weight loss
Limitations of This Calculator
This calculator provides estimates based on statistical averages. Individual results may vary due to:
- Individual metabolic differences
- Accuracy of activity level assessment
- Consistency in maintaining the calorie deficit
- Changes in physical activity over time
- Medical conditions that may affect metabolism
Always consult with a healthcare professional before starting any weight loss program.