Estimate your weight loss timeline and understand the key factors.
Calculate Your Weight Loss Projection
Enter your current weight in pounds (lbs).
Enter your target weight in pounds (lbs).
Enter your desired average weekly weight loss in pounds (lbs). (Typically 1-2 lbs/week is sustainable)
Estimate your daily calorie deficit (calories consumed vs. calories burned). (Approx. 500-1000 cal/day)
Calculated: Goal Weight – Current Weight.
Calculated: Total Weight to Lose / Target Weekly Weight Loss.
Your Weight Loss Projection
Estimated Time to Reach Goal:— weeks
Total Weight to Lose:— lbs
Projected Weekly Weight Loss:— lbs
Estimated Calories Burned Per Week:— kcal
Key Assumptions:
Daily Calorie Deficit Used:— kcal/day
Target Weight Loss Rate:— lbs/week
(Note: This is a projection. Actual results may vary based on individual metabolism, adherence to diet/exercise, and other factors.)
Weight Loss Progress Chart
Chart shows projected weight over time based on your inputs.
Weight Loss Projection Data Table
Projected Weight Over Time
Week
Weight (lbs)
Total Lost (lbs)
Cumulative Deficit (kcal)
{primary_keyword}
Understanding your {primary_keyword} is a crucial step towards achieving your fitness and health goals. A weight loss projection essentially acts as a roadmap, estimating the timeframe required to shed a specific amount of weight based on your current status and desired rate of loss. It's not just about predicting the future; it's about empowering you with realistic expectations and a clear path forward. Whether you're aiming to lose a few pounds or significantly transform your physique, knowing how long it might take can be a powerful motivator.
Who should use a {primary_keyword} calculator? Anyone embarking on a weight loss journey can benefit. This includes individuals seeking to:
Lose weight for health reasons (e.g., reducing risk of diabetes, heart disease).
Improve athletic performance.
Boost self-confidence and body image.
Prepare for a specific event.
It's particularly useful for setting achievable short-term and long-term goals. For instance, if you're aiming to lose 50 pounds, a projection can help you break it down into manageable monthly or quarterly targets, making the overall goal feel less daunting.
Common Misconceptions about {primary_keyword}:
It's set in stone: Projections are estimates. They don't account for every variable like metabolic adaptation, plateaus, or lifestyle changes.
Faster is always better: Rapid weight loss is often unsustainable and can be detrimental to health. Healthy weight loss typically ranges from 1-2 pounds per week.
Only diet matters: While diet is paramount for creating a calorie deficit, exercise plays a vital role in preserving muscle mass, boosting metabolism, and improving overall health.
The scale is the only measure: Weight loss isn't linear. Focusing solely on the number on the scale can be discouraging. Progress can also be seen in body measurements, how clothes fit, and increased energy levels.
A realistic {primary_keyword} is a tool for planning and motivation, not a rigid prediction. It helps frame your journey with informed expectations.
{primary_keyword} Formula and Mathematical Explanation
The core of any {primary_keyword} calculator lies in understanding the relationship between weight, calorie deficit, and time. The fundamental principle is that approximately 3,500 calories equate to one pound of body fat. Therefore, to lose weight, you must create a calorie deficit.
The calculation proceeds in several steps:
Calculate Total Weight to Lose: This is the difference between your current weight and your goal weight.
Determine the Required Calorie Deficit: Multiply the total weight to lose by 3,500 calories/pound to find the total calorie deficit needed.
Estimate Weekly Weight Loss Rate: This is usually provided by the user as a target (e.g., 1.5 lbs/week).
Calculate the Average Daily Calorie Deficit Needed: Divide the target weekly weight loss (in lbs) by 7 days and multiply by 3,500 calories/pound. Alternatively, the user might directly input their estimated average daily calorie deficit.
Calculate Estimated Weeks to Reach Goal: Divide the total weight to lose (in lbs) by the target weekly weight loss rate (in lbs/week).
Variables Used in the Calculator:
Variable
Meaning
Unit
Typical Range/Input
Current Weight
Your starting body weight.
lbs
100 – 1000+
Goal Weight
Your target body weight.
lbs
50 – 500+
Target Weekly Weight Loss
Desired average pounds lost per week.
lbs/week
0.5 – 3.0 (Sustainable: 1-2)
Average Daily Calorie Deficit
Difference between calories burned and consumed daily.
kcal/day
250 – 1500
Total Weight to Lose
Difference between current and goal weight.
lbs
Calculated
Estimated Weeks to Reach Goal
Calculated time needed to achieve goal weight.
weeks
Calculated
Total Calorie Deficit Needed
Total calories to eliminate for weight loss.
kcal
Calculated (Total Weight to Lose * 3500)
The formula for Estimated Weeks to Reach Goal is straightforward:
Estimated Weeks = Total Weight to Lose (lbs) / Target Weekly Weight Loss (lbs/week)
And the Average Daily Calorie Deficit Needed can be derived from the target weekly loss:
This mathematical foundation helps create the realistic projections users see.
Practical Examples (Real-World Use Cases)
Let's illustrate the {primary_keyword} calculator with practical scenarios:
Example 1: Moderate Weight Loss Goal
Scenario: Sarah wants to lose 20 pounds before her vacation in six months. She aims for a sustainable pace and understands the importance of consistency.
Inputs:
Current Weight: 160 lbs
Goal Weight: 140 lbs
Target Weekly Weight Loss: 1 lb/week
Average Daily Calorie Deficit: 500 kcal/day (derived from 1 lb/week * 3500 / 7 days)
Interpretation: At a pace of 1 pound per week, Sarah can expect to reach her goal weight of 140 lbs in approximately 20 weeks. This timeframe fits well within her six-month goal, allowing for flexibility and acknowledging that weight loss isn't always linear. The calculator confirms that a consistent 500-calorie daily deficit is the target.
Example 2: Significant Weight Loss Goal
Scenario: Mark is looking to make a significant lifestyle change and lose 50 pounds. He's committed to a consistent exercise routine and dietary changes, aiming for a slightly faster but still healthy rate.
Inputs:
Current Weight: 220 lbs
Goal Weight: 170 lbs
Target Weekly Weight Loss: 2 lbs/week
Average Daily Calorie Deficit: 1000 kcal/day (derived from 2 lb/week * 3500 / 7 days)
Interpretation: Mark's goal of losing 50 pounds at a rate of 2 pounds per week is projected to take about 25 weeks (roughly 6 months). This requires a substantial daily calorie deficit of 1000 calories, achieved through a combination of diet and exercise. The calculator highlights the commitment needed for this pace and provides a clear timeframe, helping Mark stay motivated and track his progress effectively.
How to Use This {primary_keyword} Calculator
Our {primary_keyword} Calculator is designed for simplicity and clarity, providing actionable insights into your weight loss journey. Here's how to get the most out of it:
Enter Current Weight: Accurately input your current body weight in pounds (lbs) into the "Current Weight" field.
Enter Goal Weight: Input your desired target weight in pounds (lbs) into the "Goal Weight" field. Ensure this goal is realistic and healthy.
Set Target Weekly Weight Loss: Decide on a sustainable pace for your weight loss. A common recommendation is 1-2 pounds per week. Enter this value in the "Target Weekly Weight Loss" field.
Estimate Daily Calorie Deficit: Provide your estimated average daily calorie deficit. This is the number of calories you consistently consume less than you burn through daily activities and exercise. If you're unsure, you can leave this blank and the calculator will suggest a deficit based on your target weekly loss (around 500-1000 calories/day is typical for 1-2 lbs/week loss).
Automatic Calculations: Once you input the primary values, the calculator automatically computes:
Total Weight to Lose: The difference between your current and goal weights.
Estimated Weeks to Reach Goal: The projected duration of your weight loss journey.
Estimated Calories Burned Per Week: The total calorie deficit needed weekly.
How to Read Your Results:
Main Result (Estimated Weeks): This is your primary projection. It tells you how long, on average, it might take to reach your goal weight given your inputs.
Intermediate Values: These provide context – the total amount you aim to lose, your planned weekly loss rate, and the corresponding calorie targets.
Key Assumptions: Review the calorie deficit and weekly loss rate used in the calculation. Ensure they align with your understanding of healthy and sustainable weight loss practices.
Chart and Table: Visualize your progress. The chart shows your weight trajectory over time, and the table offers a week-by-week breakdown of projected weight, total loss, and cumulative calorie deficit.
Decision-Making Guidance:
Adjust Pace: If the projected time is too long or too short for your liking, adjust your "Target Weekly Weight Loss." Remember that aiming for more than 2 lbs/week is often unsustainable and can pose health risks.
Review Calorie Deficit: Ensure your estimated daily calorie deficit is realistic. Extreme deficits can lead to muscle loss, nutrient deficiencies, and fatigue. Consult a healthcare professional or registered dietitian if unsure.
Stay Consistent: The calculator provides a projection based on consistency. Adherence to your diet and exercise plan is key to realizing these results.
Monitor and Adapt: Use the projection as a guide, not a rigid rule. Weight loss can fluctuate. Regularly reassess your progress and adjust your plan as needed.
By understanding these elements, you can use the calculator as a powerful tool to shape your weight loss strategy and celebrate milestones along the way.
Key Factors That Affect {primary_keyword} Results
While our {primary_keyword} Calculator provides a valuable estimate, numerous factors can influence the actual speed and success of your weight loss journey. Understanding these variables helps set more realistic expectations and strategies:
Metabolic Adaptation (Metabolic Slowdown): As you lose weight, your metabolism naturally slows down. Your body requires fewer calories to function because it's lighter. This means a consistent deficit might lead to slower loss over time, requiring adjustments to diet or exercise.
Muscle Mass Preservation: Aggressive calorie restriction without adequate protein intake and resistance training can lead to muscle loss. Muscle is metabolically active tissue, so losing it further slows your metabolism, making weight loss harder.
Hormonal Changes: Hormones like leptin (appetite regulation) and cortisol (stress) can impact hunger, cravings, and fat storage. Stress and poor sleep can disrupt these hormones, hindering weight loss efforts.
Dietary Adherence and Quality: Consistency is king. Even a small daily deficit adds up, but occasional high-calorie "cheat" meals or inconsistent tracking can negate progress. The *quality* of food also matters for satiety and nutrient intake.
Exercise Type and Intensity: While creating a calorie deficit primarily through diet is most effective, exercise plays a crucial role. Cardiovascular exercise burns calories, while strength training builds muscle, boosting metabolism long-term. The type and intensity of your workouts significantly impact results.
Individual Physiology and Genetics: Everyone's body responds differently. Genetics can influence body composition, fat distribution, and metabolic rate. What works rapidly for one person might take longer for another.
Water Retention and Fluctuations: Daily weight can fluctuate significantly due to hydration levels, sodium intake, carbohydrate consumption (glycogen stores), and hormonal cycles (especially in women). These are not fat loss but can mask true progress on the scale.
Age and Sex: Metabolism tends to slow with age. Additionally, hormonal differences between sexes can influence body composition and fat storage patterns.
Considering these factors allows for a more nuanced approach to weight management, moving beyond simple calorie math to a holistic health strategy.
Frequently Asked Questions (FAQ)
What is the most sustainable weekly weight loss rate?
The most sustainable and generally recommended weekly weight loss rate is 1 to 2 pounds per week. This pace is more likely to preserve muscle mass and is easier to maintain long-term, reducing the risk of burnout and rebound weight gain.
Does the calculator account for exercise?
The calculator primarily uses a "daily calorie deficit" input. This deficit can be achieved through a combination of reduced calorie intake and increased calorie expenditure (exercise). While it doesn't specifically ask for workout details, the estimated calorie deficit should reflect your overall lifestyle, including your exercise routine.
How accurate is a weight loss projection?
A {primary_keyword} projection is an estimate based on mathematical principles (3500 calories ≈ 1 lb fat). Actual results can vary significantly due to individual metabolic rates, adherence to the plan, hormonal fluctuations, sleep quality, stress levels, and body composition changes. Use it as a guide, not a definitive prediction.
What happens if I reach a weight loss plateau?
Plateaus are common and occur when your body adapts to your current calorie intake and expenditure. To overcome them, you might need to reassess your calorie deficit, increase physical activity, focus on strength training to boost metabolism, or consult with a healthcare professional or dietitian.
Should I aim for the fastest possible weight loss?
No, aiming for the fastest possible weight loss is generally not recommended. Very rapid weight loss can lead to muscle loss, nutrient deficiencies, gallstones, and is often unsustainable, increasing the likelihood of regaining the weight.
Can I use the calculator if I have a lot of weight to lose?
Yes, the calculator is suitable for significant weight loss goals. However, for very large amounts of weight loss (e.g., 100+ pounds), it's highly recommended to consult with a medical professional or a registered dietitian to ensure a safe, healthy, and sustainable plan.
How do I adjust my calorie deficit if my weight loss stalls?
If you're not losing weight as projected, you likely need to increase your calorie deficit. This could mean slightly reducing calorie intake further or increasing your physical activity. Ensure you're accurately tracking your food intake and estimating calorie burn.
What does the 'Cumulative Deficit' in the table mean?
The 'Cumulative Deficit' column shows the total estimated calorie deficit you would have achieved up to that specific week, based on your projected weight loss and the 3500 calorie/lb rule. It helps visualize the total energy imbalance required to reach your goal.
Related Tools and Internal Resources
Explore these valuable resources to further enhance your health and fitness journey:
var currentWeightInput = document.getElementById('currentWeight');
var goalWeightInput = document.getElementById('goalWeight');
var weeklyWeightLossRateInput = document.getElementById('weeklyWeightLossRate');
var weeklyCalorieDeficitInput = document.getElementById('weeklyCalorieDeficit');
var totalWeightToLoseInput = document.getElementById('totalWeightToLose');
var estimatedWeeksInput = document.getElementById('estimatedWeeks');
var resultsDiv = document.getElementById('results');
var mainResultSpan = document.getElementById('mainResult');
var resultTotalWeightToLoseSpan = document.getElementById('resultTotalWeightToLose');
var resultWeeklyWeightLossSpan = document.getElementById('resultWeeklyWeightLoss');
var resultWeeklyCalBurnSpan = document.getElementById('resultWeeklyCalBurn');
var assumedCalorieDeficitSpan = document.getElementById('assumedCalorieDeficit');
var assumedWeeklyLossRateSpan = document.getElementById('assumedWeeklyLossRate');
var dataTableBody = document.getElementById('dataTableBody');
var chart; // Declare chart variable globally
var chartContext; // Declare chart context variable globally
// Constants
var CALORIES_PER_POUND_FAT = 3500;
var DAYS_PER_WEEK = 7;
// Input validation error elements
var currentWeightError = document.getElementById('currentWeightError');
var goalWeightError = document.getElementById('goalWeightError');
var weeklyWeightLossRateError = document.getElementById('weeklyWeightLossRateError');
var weeklyCalorieDeficitError = document.getElementById('weeklyCalorieDeficitError');
var totalWeightToLoseError = document.getElementById('totalWeightToLoseError');
var estimatedWeeksError = document.getElementById('estimatedWeeksError');
// Initialize chart on load
window.onload = function() {
chartContext = document.getElementById('weightLossChart').getContext('2d');
// Initial call to update chart with default/empty data
updateChart([], []);
};
function isValidNumber(value) {
return !isNaN(parseFloat(value)) && isFinite(value);
}
function validateInput(element, errorElement, minValue, maxValue, emptyMessage, invalidMessage, rangeMessage) {
var value = element.value.trim();
var isValid = true;
if (value === ") {
errorElement.textContent = emptyMessage;
errorElement.style.display = 'block';
isValid = false;
} else {
var numValue = parseFloat(value);
if (isNaN(numValue)) {
errorElement.textContent = invalidMessage;
errorElement.style.display = 'block';
isValid = false;
} else if (numValue maxValue) {
errorElement.textContent = rangeMessage.replace('no more than', maxValue);
errorElement.style.display = 'block';
isValid = false;
} else {
errorElement.textContent = ";
errorElement.style.display = 'none';
}
}
return isValid;
}
function calculateWeightLoss() {
// Clear previous results and errors
resultsDiv.style.display = 'none';
clearTable();
var currentWeight = parseFloat(currentWeightInput.value);
var goalWeight = parseFloat(goalWeightInput.value);
var weeklyWeightLossRate = parseFloat(weeklyWeightLossRateInput.value);
var dailyCalorieDeficit = parseFloat(weeklyCalorieDeficitInput.value);
// — Input Validations —
var isCurrentWeightValid = validateInput(currentWeightInput, currentWeightError, 50, 1000, 'Current weight cannot be empty.', 'Enter a valid number for current weight.', 'Please enter a current weight of at least 50 lbs.');
var isGoalWeightValid = validateInput(goalWeightInput, goalWeightError, 50, 1000, 'Goal weight cannot be empty.', 'Enter a valid number for goal weight.', 'Please enter a goal weight of at least 50 lbs.');
var isWeeklyLossRateValid = validateInput(weeklyWeightLossRateInput, weeklyWeightLossRateError, 0.1, 5, 'Weekly weight loss rate cannot be empty.', 'Enter a valid number for weekly loss rate.', 'Please enter a weekly loss rate of at least 0.1 lbs.');
var isDailyCalorieDeficitValid = validateInput(weeklyCalorieDeficitInput, weeklyCalorieDeficitError, 100, 2000, 'Daily calorie deficit cannot be empty.', 'Enter a valid number for calorie deficit.', 'Please enter a daily calorie deficit between 100 and 2000 kcal.');
if (!isCurrentWeightValid || !isGoalWeightValid || !isWeeklyLossRateValid || !isDailyCalorieDeficitValid) {
return; // Stop if any primary input is invalid
}
// Ensure goal weight is less than current weight for loss
if (goalWeight >= currentWeight) {
goalWeightError.textContent = 'Goal weight must be less than current weight.';
goalWeightError.style.display = 'block';
return;
} else {
goalWeightError.textContent = ";
goalWeightError.style.display = 'none';
}
// — Calculations —
var totalWeightToLose = currentWeight – goalWeight;
var estimatedWeeks = totalWeightToLose / weeklyWeightLossRate;
var totalCalorieDeficitNeeded = totalWeightToLose * CALORIES_PER_POUND_FAT;
var calculatedDailyDeficitFromRate = (weeklyWeightLossRate * CALORIES_PER_POUND_FAT) / DAYS_PER_WEEK;
var calculatedWeeklyCalBurn = weeklyWeightLossRate * CALORIES_PER_POUND_FAT;
// Update read-only fields
totalWeightToLoseInput.value = totalWeightToLose.toFixed(1);
estimatedWeeksInput.value = estimatedWeeks.toFixed(1);
// — Display Results —
resultsDiv.style.display = 'block';
mainResultSpan.textContent = estimatedWeeks.toFixed(1) + ' weeks';
resultTotalWeightToLoseSpan.textContent = totalWeightToLose.toFixed(1) + ' lbs';
resultWeeklyWeightLossSpan.textContent = weeklyWeightLossRate.toFixed(1) + ' lbs/week';
resultWeeklyCalBurnSpan.textContent = calculatedWeeklyCalBurn.toFixed(0) + ' kcal';
assumedCalorieDeficitSpan.textContent = dailyCalorieDeficit.toFixed(0) + ' kcal/day';
assumedWeeklyLossRateSpan.textContent = weeklyWeightLossRate.toFixed(1) + ' lbs/week';
// — Prepare Data for Table and Chart —
var chartLabels = [];
var chartData = [];
var tableRows = [];
var currentWeightForTable = currentWeight;
var cumulativeDeficit = 0;
for (var i = 0; i 0) {
cumulativeDeficit += calculatedWeeklyCalBurn; // Add weekly burn for subsequent weeks
}
// Ensure projected weight doesn't go below goal weight for display purposes in table/chart
if (projectedWeight < goalWeight) {
projectedWeight = goalWeight;
totalLost = currentWeight – goalWeight; // Ensure total lost is accurate to goal
}
chartLabels.push('Week ' + i);
chartData.push(projectedWeight.toFixed(1));
var row = dataTableBody.insertRow();
row.innerHTML = '
'; // Display cumulative deficit
tableRows.push(row);
// Break loop if goal is reached or exceeded in the calculation
if (projectedWeight 0) {
// Ensure the final row accurately reflects reaching the goal weight
if (i < estimatedWeeks) {
var finalRow = dataTableBody.insertRow();
finalRow.innerHTML = '
' + estimatedWeeks.toFixed(1) + '
' +
'
' + goalWeight.toFixed(1) + '
' +
'
' + totalWeightToLose.toFixed(1) + '
' +
'
' + cumulativeDeficit.toFixed(0) + '
';
chartLabels.push('Goal Achieved');
chartData.push(goalWeight.toFixed(1));
}
break;
}
}
// Update the chart
updateChart(chartLabels, chartData);
}
function updateChart(labels, data) {
// Destroy previous chart instance if it exists
if (chart) {
chart.destroy();
}
// Create new chart
chart = new Chart(chartContext, {
type: 'line',
data: {
labels: labels,
datasets: [{
label: 'Projected Weight (lbs)',
data: data,
borderColor: 'rgb(0, 74, 153)', // Primary color
backgroundColor: 'rgba(0, 74, 153, 0.2)',
fill: true,
tension: 0.1
},
{
label: 'Goal Weight Line',
data: Array(labels.length).fill(parseFloat(goalWeightInput.value || 0)), // Use goal weight value
borderColor: 'rgb(40, 167, 69)', // Success color
borderDash: [5, 5], // Dashed line
fill: false,
tension: 0
}]
},
options: {
responsive: true,
maintainAspectRatio: true,
scales: {
y: {
beginAtZero: false,
title: {
display: true,
text: 'Weight (lbs)'
}
},
x: {
title: {
display: true,
text: 'Time'
}
}
},
plugins: {
legend: {
position: 'top',
},
title: {
display: true,
text: 'Projected Weight Loss Over Time'
}
}
}
});
}
function clearTable() {
dataTableBody.innerHTML = ";
}
function resetCalculator() {
currentWeightInput.value = '180';
goalWeightInput.value = '150';
weeklyWeightLossRateInput.value = '1.5';
weeklyCalorieDeficitInput.value = '750';
// Trigger calculation and reset errors
calculateWeightLoss();
clearErrorMessages();
}
function clearErrorMessages() {
currentWeightError.textContent = "; currentWeightError.style.display = 'none';
goalWeightError.textContent = "; goalWeightError.style.display = 'none';
weeklyWeightLossRateError.textContent = "; weeklyWeightLossRateError.style.display = 'none';
weeklyCalorieDeficitError.textContent = "; weeklyCalorieDeficitError.style.display = 'none';
totalWeightToLoseError.textContent = "; totalWeightToLoseError.style.display = 'none';
estimatedWeeksError.textContent = "; estimatedWeeksError.style.display = 'none';
}
function copyResults() {
var resultsText = "— Weight Loss Projection Results —\n\n";
resultsText += "Main Result:\n";
resultsText += document.getElementById('results-title').textContent + ": " + mainResultSpan.textContent + "\n\n";
resultsText += "Key Values:\n";
resultsText += "Total Weight to Lose: " + resultTotalWeightToLoseSpan.textContent + "\n";
resultsText += "Projected Weekly Weight Loss: " + resultWeeklyWeightLossSpan.textContent + "\n";
resultsText += "Estimated Calories Burned Per Week: " + resultWeeklyCalBurnSpan.textContent + "\n\n";
resultsText += "Assumptions:\n";
resultsText += "Assumed Daily Calorie Deficit: " + assumedCalorieDeficitSpan.textContent + "\n";
resultsText += "Assumed Target Weight Loss Rate: " + assumedWeeklyLossRateSpan.textContent + "\n\n";
resultsText += "Note: This is a projection. Actual results may vary.\n";
// Create a temporary textarea element to copy text
var textArea = document.createElement("textarea");
textArea.value = resultsText;
textArea.style.position = "fixed";
textArea.style.left = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied!' : 'Copying failed.';
// Optionally provide user feedback, e.g., a temporary alert or status message
console.log(msg);
// alert(msg); // Use alert cautiously; inline messages are preferred for UX
} catch (err) {
console.error('Fallback: Oops, unable to copy', err);
// alert('Fallback: Oops, unable to copy. Please copy manually.');
}
document.body.removeChild(textArea);
}
function toggleFaq(element) {
var paragraph = element.nextElementSibling;
if (paragraph.style.display === "block") {
paragraph.style.display = "none";
} else {
paragraph.style.display = "block";
}
}
// Add event listeners to recalculate when inputs change
currentWeightInput.addEventListener('input', calculateWeightLoss);
goalWeightInput.addEventListener('input', calculateWeightLoss);
weeklyWeightLossRateInput.addEventListener('input', calculateWeightLoss);
weeklyCalorieDeficitInput.addEventListener('input', calculateWeightLoss);
// Initial calculation on page load
window.addEventListener('load', function() {
// Ensure chart context is available before initial calculation
if (!chartContext) {
chartContext = document.getElementById('weightLossChart').getContext('2d');
}
calculateWeightLoss(); // Perform initial calculation
});