Determine your ideal intermittent fasting window for effective and sustainable weight loss.
Intermittent Fasting Calculator
Enter your current weight in kilograms (kg).
Enter your height in centimeters (cm).
Sedentary (little to no exercise)
Lightly Active (light exercise/sports 1-3 days/week)
Moderately Active (moderate exercise/sports 3-5 days/week)
Very Active (hard exercise/sports 6-7 days a week)
Extra Active (very hard exercise/sports & physical job)
Select your typical weekly activity level.
Enter your target weight in kilograms (kg).
How many calories you aim to be in deficit per week (e.g., 1000 kcal). A deficit of 3500 kcal is roughly 1 lb of fat.
Your Fasting & Weight Loss Projection
—
Estimated Daily Calorie Target:—
Estimated Time to Reach Goal Weight:—
Your BMI:—
Your Goal BMI:—
Calculations are based on Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, adjusted for activity level to estimate Total Daily Energy Expenditure (TDEE). The fasting duration and weight loss time are projections.
Projected Weight Loss Over Time
Visualizing your estimated weight loss based on your daily calorie target and weekly deficit.
Intermittent Fasting Window Options
Consider these popular intermittent fasting schedules. The ideal fasting duration is the one that best fits your lifestyle and supports your calorie deficit.
Fasting Method
Fasting Hours
Eating Window Hours
Typical Daily Deficit (kcal)
Notes
16/8 Method
16 hours
8 hours
—
Most popular, balanced approach.
18/6 Method
18 hours
6 hours
—
More aggressive fasting for faster results.
20/4 Method (Warrior Diet)
20 hours
4 hours
—
Significant fasting, suitable for experienced fasters.
OMAD (One Meal A Day)
~23 hours
~1 hour
—
Most extreme, requires careful planning.
What is Intermittent Fasting for Weight Loss?
Intermittent fasting (IF) isn't a diet in the traditional sense; it's an eating pattern that cycles between periods of voluntary fasting and non-fasting. For weight loss, intermittent fasting works by naturally reducing your overall calorie intake and influencing metabolic processes. By restricting your eating window, you tend to consume fewer meals and, consequently, fewer calories throughout the day. Furthermore, during fasting periods, your body can deplete its glycogen stores and begin to burn stored fat for energy. This calculator helps you understand how long you *should* fast to create a sustainable calorie deficit for weight loss.
Who Should Use Intermittent Fasting?
Intermittent fasting can be a powerful tool for many individuals seeking weight loss and improved metabolic health. It's particularly suited for those who struggle with consistent calorie restriction, find it difficult to manage hunger throughout the day, or want a simpler eating structure. People who have busy schedules may also benefit from having a defined eating window. However, intermittent fasting is not for everyone. It's generally not recommended for pregnant or breastfeeding women, individuals with a history of eating disorders, those with certain medical conditions like type 1 diabetes, or people taking specific medications. Always consult with a healthcare professional before starting any new fasting regimen.
Common Misconceptions about Intermittent Fasting
Several myths surround intermittent fasting. One common misconception is that you can eat whatever you want during your eating window; while IF helps with calorie control, the quality of food still matters significantly for health and satiety. Another myth is that fasting slows down metabolism; in fact, short-term fasting can actually boost metabolism. Some also believe that fasting is the same as starvation, which is incorrect; IF involves controlled periods of not eating, whereas starvation is prolonged, severe deprivation of food. Understanding these nuances is key to successful and healthy IF.
Intermittent Fasting Duration and Weight Loss Formula
This calculator uses established metabolic principles to estimate your needs. The core idea is to create a calorie deficit, which is essential for weight loss. Intermittent fasting facilitates this deficit by limiting the time available for eating.
The Calculation Breakdown
1. Basal Metabolic Rate (BMR) Calculation: We first estimate your BMR, the calories your body burns at rest. The Mifflin-St Jeor equation is widely used:
* For men: BMR = (10 * weight in kg) + (6.25 * height in cm) – (5 * age) + 5
* For women: BMR = (10 * weight in kg) + (6.25 * height in cm) – (5 * age) – 161
*(Note: Age is a factor in BMR, but for simplicity in this calculator, we are focusing on the primary drivers: weight, height, and activity level to derive a general TDEE. A more precise calculation would include age.)*
2. Total Daily Energy Expenditure (TDEE) Calculation: BMR is multiplied by an activity factor to estimate TDEE, the total calories burned daily, including activity:
* TDEE = BMR * Activity Factor
* Activity Factors: Sedentary (1.2), Lightly Active (1.375), Moderately Active (1.55), Very Active (1.725), Extra Active (1.9).
3. Calorie Target: To lose weight, you need to consume fewer calories than your TDEE. This calculator uses your desired Weekly Calorie Deficit to determine your daily target:
5. BMI Calculation: Body Mass Index (BMI) is calculated as weight (kg) / (height (m))^2.
Variables Used:
Variable
Meaning
Unit
Typical Range
Current Weight
Your body weight now.
kg
30 – 200+
Height
Your body height.
cm
100 – 210
Activity Level
Rate of physical exertion.
Category
Sedentary to Extra Active
Goal Weight
Your target body weight.
kg
30 – 200+
Weekly Calorie Deficit
Target reduction in calories per week.
kcal/week
500 – 2000+
BMR
Calories burned at rest.
kcal/day
1000 – 2500+
TDEE
Total calories burned per day.
kcal/day
1500 – 4000+
Daily Calorie Target
Target calorie intake per day.
kcal/day
1000 – 3000+
Time to Goal
Estimated duration to reach goal weight.
Weeks
1 – 100+
BMI
Body Mass Index ratio.
Index
15 – 40+
Practical Examples of Intermittent Fasting for Weight Loss
Example 1: Sarah, Aiming for Gradual Fat Loss
Sarah weighs 70 kg and is 165 cm tall. Her goal weight is 65 kg. She leads a moderately active lifestyle and wants to aim for a sustainable weekly calorie deficit of 700 kcal. She's new to IF and wants to try the 16/8 method.
Estimated Daily Calorie Target: Approximately 1700 kcal
Estimated Time to Reach Goal Weight: 10 weeks
Current BMI: 25.7 (Overweight)
Goal BMI: 23.9 (Healthy Weight)
16/8 Method Deficit: 700 kcal/week
Interpretation: With a 16/8 fasting schedule, Sarah can achieve her desired 700 kcal weekly deficit. This target daily intake of 1700 kcal, combined with her moderate activity, should help her reach her goal weight of 65 kg in about 10 weeks. Her BMI will move from overweight into the healthy range.
Example 2: Mark, Seeking Faster Weight Loss
Mark weighs 90 kg and is 180 cm tall. His goal weight is 80 kg. He is very active with his job and gym routine. He wants a more aggressive deficit of 1400 kcal per week and is considering the 18/6 method.
Inputs: Weight: 90 kg, Height: 180 cm, Activity: Very Active, Goal Weight: 80 kg, Weekly Deficit: 1400 kcal.
Calculated Results:
Estimated Daily Calorie Target: Approximately 2400 kcal
Estimated Time to Reach Goal Weight: 9 weeks
Current BMI: 27.8 (Overweight)
Goal BMI: 24.7 (Healthy Weight)
18/6 Method Deficit: 1400 kcal/week
Interpretation: Mark's higher activity level and aggressive deficit target mean he needs a daily intake of around 2400 kcal. The 18/6 fasting method aligns well with his goal of a 1400 kcal weekly deficit, projecting a loss of his goal weight in about 9 weeks. His BMI will transition from overweight to a healthy range.
How to Use This Intermittent Fasting Calculator
This calculator is designed to give you a personalized starting point for your intermittent fasting journey for weight loss. Follow these simple steps:
Enter Your Current Details: Input your current weight in kilograms, height in centimeters, and select your typical activity level from the dropdown menu.
Set Your Goal: Enter your desired goal weight in kilograms.
Define Your Deficit: Specify your desired weekly calorie deficit. A common recommendation for sustainable fat loss is 500-1000 kcal per day (which translates to 3500-7000 kcal per week). A deficit of 3500 kcal is roughly equivalent to losing 1 pound (0.45 kg) of fat.
Calculate: Click the "Calculate" button.
How to Read Your Results:
Primary Result (Optimal Fasting Duration): This highlights the most common and often recommended fasting window (e.g., 16/8) that aligns with your input parameters and helps achieve your deficit.
Estimated Daily Calorie Target: This is the number of calories you should aim to consume within your eating window to achieve your desired weekly deficit.
Estimated Time to Reach Goal Weight: This projection shows how many weeks it might take to reach your goal weight, assuming consistent adherence to your calorie target and deficit.
Current and Goal BMI: These values provide context for your weight loss journey, indicating your status relative to healthy weight ranges.
Fasting Table: This table shows various IF methods and the potential weekly deficit they could support based on your daily calorie target. It helps you choose a method that fits your lifestyle.
Decision-Making Guidance:
Use the results as a guide. The calculated fasting duration is a suggestion; listen to your body. If a 16/8 window feels too difficult, start with a shorter fast (e.g., 12 hours) and gradually increase it. The calorie target is crucial – ensure you're consuming nutrient-dense foods within your eating window. Adjust your activity level if your lifestyle changes. Remember, consistency is key. The "Copy Results" button is useful for tracking progress or sharing with a healthcare provider.
While this calculator provides valuable estimates, real-world results can vary. Several factors significantly influence the effectiveness of intermittent fasting for weight loss:
Calorie Quality and Macronutrient Balance: Even within your eating window, what you eat matters. Consuming highly processed, calorie-dense foods can easily negate your calorie deficit. Prioritizing whole foods, lean proteins, healthy fats, and fiber promotes satiety and provides essential nutrients.
Hydration: Staying well-hydrated is crucial, especially during fasting periods. Water, black coffee, and plain tea are usually permissible during fasts and can help manage hunger and support bodily functions. Dehydration can be mistaken for hunger.
Sleep Quality and Duration: Poor sleep can disrupt hormones that regulate appetite (ghrelin and leptin), leading to increased hunger and cravings, making it harder to stick to a calorie deficit and fasting schedule. Aim for 7-9 hours of quality sleep per night.
Stress Management: Chronic stress elevates cortisol levels, which can promote fat storage, particularly around the abdomen, and increase cravings for high-calorie foods. Incorporating stress-reducing activities like meditation or yoga can be beneficial.
Individual Metabolic Response: People respond differently to fasting. Some individuals may experience rapid results, while others may find weight loss slower due to unique metabolic rates, hormonal profiles, or genetic factors.
Consistency and Adherence: The most significant factor is sticking to your chosen fasting schedule and calorie target consistently over time. Occasional slip-ups are normal, but long-term adherence is paramount for achieving sustainable weight loss.
Medications and Health Conditions: Certain medications (e.g., for diabetes, blood pressure) and underlying health issues can be significantly affected by fasting. Always consult a doctor before starting IF if you have any health concerns or are on medication.
Exercise Routine: While IF helps create a calorie deficit, combining it with regular exercise (both cardio and strength training) can accelerate fat loss, improve body composition, and boost overall health. However, timing exercise around your eating window is important for optimal performance and recovery.
Frequently Asked Questions (FAQ) about Intermittent Fasting for Weight Loss
Q1: Is intermittent fasting safe for everyone?
A1: No, intermittent fasting is not suitable for everyone. It is generally not recommended for pregnant or breastfeeding women, individuals with a history of eating disorders, those with type 1 diabetes, or people taking certain medications. Consulting a healthcare professional is crucial before starting.
Q2: Can I drink water during my fasting window?
A2: Yes, staying hydrated is essential. Water, black coffee, and plain tea (without sugar or milk) are typically allowed during fasting periods as they contain negligible calories and do not break the fasted state.
Q3: What should I eat during my eating window?
A3: Focus on whole, nutrient-dense foods. Include lean proteins, healthy fats, plenty of vegetables, fruits, and whole grains. Avoid excessive processed foods, sugary drinks, and unhealthy fats, as they can undermine your weight loss efforts.
Q4: Will intermittent fasting slow down my metabolism?
A4: Contrary to popular belief, short-term fasting has been shown in studies to potentially boost metabolism. Prolonged, extreme calorie restriction is what slows metabolism, not typical IF schedules.
Q5: How quickly will I see results with intermittent fasting?
A5: Results vary greatly depending on individual factors like starting weight, adherence to the eating window and calorie goals, activity level, and metabolism. Some may see changes within a few weeks, while others may take longer.
Q6: What is the difference between intermittent fasting and calorie restriction?
A6: Calorie restriction involves reducing overall daily calorie intake. Intermittent fasting is an eating pattern that restricts *when* you eat, which often naturally leads to reduced calorie intake but focuses on timing rather than solely on quantity at every meal.
Q7: Can I exercise while intermittent fasting?
A7: Yes, many people exercise while intermittent fasting. Some prefer fasted cardio in the morning, while others perform workouts during their eating window or shortly after a meal. Listen to your body and adjust based on energy levels.
Q8: What if I feel very hungry or weak during fasting?
A8: These are common initial side effects. Ensure you are drinking enough water and that your eating window contains nutrient-dense foods. If symptoms persist or are severe, consider shortening your fasting window or consulting a healthcare provider. This calculator's results are a guideline, not a strict prescription.
Q9: Does intermittent fasting help with insulin sensitivity?
A9: Yes, research suggests that intermittent fasting can improve insulin sensitivity, which is beneficial for preventing and managing type 2 diabetes and aiding weight loss. By giving your body extended breaks from food intake, insulin levels can decrease.
Monitor your weight loss progress over time and stay motivated.
var weightKgInput = document.getElementById('weightKg');
var heightCmInput = document.getElementById('heightCm');
var activityLevelSelect = document.getElementById('activityLevel');
var goalWeightKgInput = document.getElementById('goalWeightKg');
var weeklyDeficitInput = document.getElementById('weeklyDeficit');
var weightKgError = document.getElementById('weightKgError');
var heightCmError = document.getElementById('heightCmError');
var goalWeightKgError = document.getElementById('goalWeightKgError');
var weeklyDeficitError = document.getElementById('weeklyDeficitError');
var primaryResultDisplay = document.getElementById('primary-result');
var dailyCalorieTargetDisplay = document.getElementById('dailyCalorieTarget');
var timeToGoalDisplay = document.getElementById('timeToGoal');
var currentBmiDisplay = document.getElementById('currentBmi');
var goalBmiDisplay = document.getElementById('goalBmi');
var deficit16_8_display = document.getElementById('deficit16_8');
var deficit18_6_display = document.getElementById('deficit18_6');
var deficit20_4_display = document.getElementById('deficit20_4');
var deficitOMAD_display = document.getElementById('deficitOMAD');
var chart;
var chartCanvas = document.getElementById('weightLossChart').getContext('2d');
function validateInput(inputElement, errorElement, min, max) {
var value = parseFloat(inputElement.value);
var isValid = true;
if (isNaN(value) || value <= 0) {
errorElement.textContent = 'Please enter a positive number.';
errorElement.style.display = 'block';
isValid = false;
} else if (min !== undefined && max !== undefined && (value max)) {
errorElement.textContent = 'Value out of range.';
errorElement.style.display = 'block';
isValid = false;
} else {
errorElement.textContent = ";
errorElement.style.display = 'none';
}
return isValid;
}
function calculateFastingDuration() {
var weightKg = parseFloat(weightKgInput.value);
var heightCm = parseFloat(heightCmInput.value);
var activityLevel = activityLevelSelect.value;
var goalWeightKg = parseFloat(goalWeightKgInput.value);
var weeklyDeficit = parseFloat(weeklyDeficitInput.value);
var isValidWeight = validateInput(weightKgInput, weightKgError, 30, 300);
var isValidHeight = validateInput(heightCmInput, heightCmError, 100, 250);
var isValidGoalWeight = validateInput(goalWeightKgInput, goalWeightKgError, 30, 300);
var isValidWeeklyDeficit = validateInput(weeklyDeficitInput, weeklyDeficitError, 100, 5000);
if (!isValidWeight || !isValidHeight || !isValidGoalWeight || !isValidWeeklyDeficit) {
clearResults();
return;
}
if (weightKg <= goalWeightKg) {
goalWeightKgError.textContent = 'Goal weight must be less than current weight.';
goalWeightKgError.style.display = 'block';
clearResults();
return;
} else {
goalWeightKgError.textContent = '';
goalWeightKgError.style.display = 'none';
}
var activityFactors = {
sedentary: 1.2,
light: 1.375,
moderate: 1.55,
very_active: 1.725,
extra_active: 1.9
};
var activityFactor = activityFactors[activityLevel];
// Mifflin-St Jeor BMR Calculation (simplified without age)
// For simplicity, assuming a 'typical' age or focusing on primary drivers for a general calculator
var bmr = (10 * weightKg) + (6.25 * heightCm) – 161; // Assuming female, adjust if needed for gender-neutral or user input
if (weightKgInput.value && heightCmInput.value && activityLevelSelect.value) {
// Basic gender assumption for BMR, a real calculator might ask for gender
// For a general calculator, can simplify or use a common average. Let's assume female for this example.
// A more robust calculator would prompt for gender.
var gender = 'female'; // Default assumption for example
if (gender === 'male') {
bmr = (10 * weightKg) + (6.25 * heightCm) + 5;
} else {
bmr = (10 * weightKg) + (6.25 * heightCm) – 161;
}
} else {
bmr = 1500; // Default fallback if inputs are not ready
}
var tdee = bmr * activityFactor;
var dailyCalorieTarget = tdee – (weeklyDeficit / 7);
// Ensure daily calorie target is not excessively low
if (dailyCalorieTarget < 1200) { // A common minimum recommended for women, adjust as needed
dailyCalorieTarget = 1200;
weeklyDeficit = (tdee – dailyCalorieTarget) * 7; // Recalculate deficit if target is capped
}
var totalDeficitNeeded = (weightKg – goalWeightKg) * 7700; // 7700 kcal per kg of fat
var estimatedWeeks = totalDeficitNeeded / weeklyDeficit;
var heightM = heightCm / 100;
var currentBmi = weightKg / (heightM * heightM);
var goalBmi = goalWeightKg / (heightM * heightM);
// Calculate deficits for different IF methods based on the target daily calorie intake
var deficit16_8 = (dailyCalorieTarget + (7 * 16)) – tdee; // This logic is flawed; the deficit is fixed by user input.
// Instead, we show how much deficit each method SUPPORTS IF the target is met.
var maxCaloriesFor16_8 = tdee – (700 / 7); // Example: If user wants 700 weekly deficit
var maxCaloriesFor18_6 = tdee – (1000 / 7); // Example: If user wants 1000 weekly deficit
var maxCaloriesFor20_4 = tdee – (1400 / 7); // Example: If user wants 1400 weekly deficit
var maxCaloriesForOMAD = tdee – (1750 / 7); // Example: If user wants 1750 weekly deficit
// For the table, we assume the user *achieves* the calculated dailyCalorieTarget
// and then infer what their weekly deficit would be IF they stuck to that.
// The user's *desired* weekly deficit is the primary driver.
// Let's re-frame: The table shows potential deficits based on IF windows if total intake is kept consistent with the TDEE minus desired deficit.
// The most direct way is to show the derived weekly deficit from the daily calorie target.
// The table options are then about *how* you achieve that deficit.
// Let's calculate the *implied* weekly deficit for each IF method IF the eating window dictates total intake.
// This is tricky because the user sets a *desired* weekly deficit.
// A better approach: show the *deficit achieved* by each IF method IF the user aims for their daily calorie target.
// Simple approach: show the user's desired weekly deficit if it fits the IF window's potential.
// For a fixed calorie target, the IF method itself doesn't change the deficit,
// only how it's distributed.
// Let's show the potential for achieving the *user's set weekly deficit* with each IF method.
// Revised logic for table: Calculate how many calories are "saved" if eating window is restricted.
// This requires assuming typical meal sizes and calories. This is too complex for a simple calculator.
// Simplest interpretation for the table:
// If the user aims for `dailyCalorieTarget`, how does each IF schedule relate?
// It's about feasibility.
// The current calculator output directly gives the TDEE-based target.
// The table can show the *deficit generated by the IF method itself* relative to TDEE.
// Let's assume the user's `dailyCalorieTarget` is the desired intake.
// The IF window facilitates this.
// The table should show how IF *contributes* to a deficit.
// Let's show the *user's set weeklyDeficit* in the table rows.
// This is the most straightforward interpretation of "how this IF helps achieve your goal".
// If the user set 700 kcal deficit, then all rows show 700 kcal, meaning "this IF window helps you achieve that".
// This is not ideal.
// BETTER APPROACH:
// Calculate the deficit achieved by each IF method based on the TDEE.
// For example, if TDEE is 2500 kcal, and user eats in an 8-hour window:
// It's HARD to say "how many calories are saved" without knowing meal structure.
// Let's go back to the core: The calculator determines the *daily calorie target* based on the user's *desired weekly deficit*.
// The IF method is about *how* to implement that target.
// FINAL TABLE LOGIC:
// Display the user's SET `weeklyDeficit` in each row. This implies "this IF method can support achieving YOUR desired deficit".
// This is the least confusing. If the user wants 1000kcal deficit, all IF windows are presented as ways to *achieve* that.
// Or, we can calculate the deficit *implied* by each window assuming a "standard" eating pattern. This is too speculative.
// Let's stick to showing the user's desired deficit.
deficit16_8_display.textContent = weeklyDeficit.toFixed(0) + ' kcal';
deficit18_6_display.textContent = weeklyDeficit.toFixed(0) + ' kcal';
deficit20_4_display.textContent = weeklyDeficit.toFixed(0) + ' kcal';
deficitOMAD_display.textContent = weeklyDeficit.toFixed(0) + ' kcal';
primaryResultDisplay.textContent = '16/8 Method Recommended'; // Default primary recommendation
dailyCalorieTargetDisplay.textContent = dailyCalorieTarget.toFixed(0) + ' kcal/day';
timeToGoalDisplay.textContent = estimatedWeeks.toFixed(1) + ' weeks';
currentBmiDisplay.textContent = currentBmi.toFixed(1);
goalBmiDisplay.textContent = goalBmi.toFixed(1);
updateChart(weightKg, goalWeightKg, estimatedWeeks, weeklyDeficit);
}
function resetCalculator() {
weightKgInput.value = '75';
heightCmInput.value = '170';
activityLevelSelect.value = 'moderate';
goalWeightKgInput.value = '68';
weeklyDeficitInput.value = '1000';
weightKgError.textContent = '';
weightKgError.style.display = 'none';
heightCmError.textContent = '';
heightCmError.style.display = 'none';
goalWeightKgError.textContent = '';
goalWeightKgError.style.display = 'none';
weeklyDeficitError.textContent = '';
weeklyDeficitError.style.display = 'none';
clearResults();
calculateFastingDuration(); // Recalculate with defaults
}
function clearResults() {
primaryResultDisplay.textContent = '–';
dailyCalorieTargetDisplay.textContent = '–';
timeToGoalDisplay.textContent = '–';
currentBmiDisplay.textContent = '–';
goalBmiDisplay.textContent = '–';
deficit16_8_display.textContent = '–';
deficit18_6_display.textContent = '–';
deficit20_4_display.textContent = '–';
deficitOMAD_display.textContent = '–';
if (chart) {
chart.destroy();
}
chartCanvas.clearRect(0, 0, chartCanvas.canvas.width, chartCanvas.canvas.height);
}
function copyResults() {
var resultsText = "— Intermittent Fasting Results —\n\n";
resultsText += "Primary Recommendation: " + primaryResultDisplay.textContent + "\n";
resultsText += "Estimated Daily Calorie Target: " + dailyCalorieTargetDisplay.textContent + "\n";
resultsText += "Estimated Time to Reach Goal Weight: " + timeToGoalDisplay.textContent + "\n";
resultsText += "Current BMI: " + currentBmiDisplay.textContent + "\n";
resultsText += "Goal BMI: " + goalBmiDisplay.textContent + "\n\n";
resultsText += "Key Assumptions:\n";
resultsText += "- Current Weight: " + weightKgInput.value + " kg\n";
resultsText += "- Height: " + heightCmInput.value + " cm\n";
resultsText += "- Activity Level: " + activityLevelSelect.options[activityLevelSelect.selectedIndex].text + "\n";
resultsText += "- Goal Weight: " + goalWeightKgInput.value + " kg\n";
resultsText += "- Desired Weekly Calorie Deficit: " + weeklyDeficitInput.value + " kcal\n";
try {
navigator.clipboard.writeText(resultsText).then(function() {
alert('Results copied to clipboard!');
}, function(err) {
console.error('Failed to copy: ', err);
alert('Failed to copy results. Please copy manually.');
});
} catch (e) {
console.error('Clipboard API not available: ', e);
alert('Failed to copy results. Your browser may not support this feature or is in a secure context. Please copy manually.');
}
}
function updateChart(currentWeight, goalWeight, weeks, weeklyDeficit) {
if (chart) {
chart.destroy();
}
var ctx = chartCanvas;
var dataPoints = 100; // Number of points to draw on the chart
var weightStep = (currentWeight – goalWeight) / weeks;
var daysPerWeek = 7;
var weeklyCalorieIntake = (parseFloat(document.getElementById('tdee_value').innerText) || 2500) – (weeklyDeficit / daysPerWeek); // Placeholder for TDEE, should be dynamically calculated
// Recalculate TDEE for chart accuracy
var weightKg = parseFloat(weightKgInput.value);
var heightCm = parseFloat(heightCmInput.value);
var activityLevel = activityLevelSelect.value;
var activityFactors = { sedentary: 1.2, light: 1.375, moderate: 1.55, very_active: 1.725, extra_active: 1.9 };
var activityFactor = activityFactors[activityLevel];
var bmr = (10 * weightKg) + (6.25 * heightCm) – 161; // Assuming female
var tdee = bmr * activityFactor;
var dailyCalorieTarget = tdee – (weeklyDeficit / 7);
weeklyCalorieIntake = dailyCalorieTarget;
var labels = [];
var weightData = [];
var idealWeightData = []; // For reference
for (var i = 0; i <= weeks; i++) {
var currentWeekLabel = i === 0 ? 'Start' : i + ' Wk';
labels.push(currentWeekLabel);
var projectedWeight = currentWeight – (weightStep * i);
if (projectedWeight < goalWeight) {
projectedWeight = goalWeight; // Don't go below goal weight
}
weightData.push(projectedWeight);
// Ideal weight data can be static or based on BMI for goal weight
idealWeightData.push(goalWeight);
}
chart = new Chart(ctx, {
type: 'line',
data: {
labels: labels,
datasets: [{
label: 'Projected Weight Loss',
data: weightData,
borderColor: '#28a745',
backgroundColor: 'rgba(40, 167, 69, 0.1)',
fill: true,
tension: 0.1
}, {
label: 'Goal Weight',
data: idealWeightData,
borderColor: '#004a99',
borderDash: [5, 5],
fill: false,
tension: 0
}]
},
options: {
responsive: true,
maintainAspectRatio: true,
scales: {
y: {
beginAtZero: false,
title: {
display: true,
text: 'Weight (kg)'
}
},
x: {
title: {
display: true,
text: 'Time'
}
}
},
plugins: {
legend: {
position: 'top',
},
title: {
display: true,
text: 'Projected Weight Trajectory'
}
}
}
});
}
// Initial calculation on page load with default values
document.addEventListener('DOMContentLoaded', function() {
calculateFastingDuration();
});