حاسبة TDEE - إجمالي استهلاك الطاقة اليومي

Total daily energy expenditure (TDEE) is an estimate of how many calories a person burns in an average day, combining resting metabolism with the energy spent on digestion, daily movement and exercise. It is commonly used as the starting point for setting a calorie target, whether the goal is to maintain weight, lose fat gradually or support muscle gain. Because it relies on population-based equations, the figure is an informed estimate rather than a measured value.

المعادلة

TDEE = BMR x activity multiplier; BMR (men) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age(years) + 5; BMR (women) = 10 x weight(kg) + 6.25 x height(cm) - 5 x age(years) - 161

• weight = body weight in kilograms
• height = standing height in centimetres
• age = age in completed years
• activity multiplier = a factor from about 1.2 (sedentary) to about 1.9 (very hard training or physical job)

Mifflin-St Jeor equation, published in the American Journal of Clinical Nutrition in 1990, derived from measured resting energy expenditure in 498 healthy adults; the activity multipliers are a widely used adaptation of the Harris-Benedict activity scale.

How the calculation works

The calculation happens in two steps. First, basal metabolic rate (BMR), the energy the body needs at complete rest just to keep the heart beating, lungs breathing and organs functioning, is estimated from weight, height, age and sex using the Mifflin-St Jeor equation. This equation was developed from direct measurements of resting energy expenditure and has been shown in later validation studies to be one of the more accurate predictive equations available for people without severe obesity.

Second, BMR is multiplied by an activity factor that scales it up to reflect a typical day, including work, chores, exercise and incidental movement. A sedentary office worker who does little deliberate exercise might use a multiplier around 1.2, while someone training hard six or seven days a week, or doing physically demanding manual labour, might use a multiplier closer to 1.7 to 1.9. The result, TDEE, is the estimated number of calories that would keep body weight roughly stable at the current activity level.

How to read your result

TDEE is typically used as a baseline for setting calorie targets. Eating close to TDEE tends to maintain current weight over time; a sustained calorie deficit below TDEE tends to produce weight loss, and a sustained surplus above it tends to produce weight gain. The table below shows commonly used activity multipliers and what they roughly represent.

Using TDEE to set a calorie target

Because a kilogram of body fat represents roughly 7,700 kilocalories of stored energy, about 3,500 kilocalories per pound, a daily deficit or surplus of 250 to 500 kilocalories below or above TDEE is commonly used to aim for a change of roughly 0.25 to 0.5 kilograms a week. Larger deficits are sometimes used under medical or dietetic supervision, but very low intakes increase the risk of muscle loss, nutrient shortfalls and difficulty sustaining the plan.

TDEE estimates drift over time as weight, muscle mass and activity change, so the figure is best treated as a starting point to test and adjust: track weight and intake for two to three weeks, then revise the target if actual progress differs noticeably from what the calculation predicted.

Why TDEE estimates drift as you diet

TDEE is not fixed even at a stable activity level. As body weight falls, BMR falls too, partly because there is simply less tissue to maintain, but total expenditure can drop by more than that alone. Sustained, significant calorie deficits trigger a degree of metabolic adaptation, in which the body reduces energy expenditure beyond what reduced body mass alone would predict, partly through lower non-exercise activity thermogenesis, or NEAT, the energy spent on fidgeting, posture and incidental daily movement that people often reduce without noticing when calories are restricted. Research on contestants from the television show The Biggest Loser, published in the journal Obesity in 2016, documented resting metabolic rates substantially below predicted values even six years after the competition, illustrating how persistent this adaptation can be after a large, rapid weight loss.

NEAT itself can vary by several hundred kilocalories a day between individuals of similar size, driven by things as simple as how much a person paces, stands or fidgets through the day. This is one reason two people with matching TDEE calculator results can have measurably different real-world energy needs, and why the calculator output works best as a first estimate to be tested and adjusted against tracked results, not treated as a fixed number.

• Recalculate TDEE after a meaningful weight change, roughly every 4.5 to 7 kilograms lost or gained, rather than relying on the figure from the start of a diet.
• If weight loss stalls despite an accurate calorie deficit, some slowing is expected from metabolic adaptation; check calorie logging accuracy before assuming the target itself is wrong.
• Non-exercise activity, such as walking, standing and fidgeting, can vary energy needs by several hundred kilocalories a day between similarly sized people, and is a common reason two people with the same TDEE differ in practice.

حدود الاستخدام

• The Mifflin-St Jeor equation was derived from a mainly non-obese adult population and tends to be less accurate at the extremes of body size, including significant obesity or very low body weight.
• It has not been validated for children, adolescents, or pregnant or breastfeeding women, all of whom have different metabolic demands.
• Activity multipliers are broad categories based on self-reported habits; two people who both describe themselves as moderately active can have genuinely different real-world energy expenditure.
• The equation does not account for medical conditions that alter metabolism, such as thyroid disorders, or for medications that affect appetite or energy use.
• It does not separately account for high muscle mass; very muscular individuals may have a higher BMR than the equation predicts, since muscle tissue is more metabolically active than fat tissue.

الأسئلة الشائعة

Is TDEE the same as the calories I should eat to lose weight?

No. TDEE is an estimate of maintenance calories, the amount that tends to keep weight stable. To lose weight, most approaches use a moderate deficit below TDEE, commonly 250 to 500 kilocalories a day, rather than eating at TDEE itself.

Why does my TDEE change over time?

TDEE depends on current weight, muscle mass, age and activity level, all of which shift over months and years. As weight is lost, BMR typically falls somewhat because there is less tissue to maintain, which is why calorie targets often need periodic recalculation.

How accurate are TDEE calculators?

Predictive equations like Mifflin-St Jeor generally estimate resting energy expenditure within about 10 percent of measured values for most non-obese adults, but individual metabolism varies. The activity multiplier adds further uncertainty, since it relies on a rough self-assessment of daily movement rather than a direct measurement.

What is the difference between BMR and TDEE?

BMR is the energy used at complete rest for basic survival functions. TDEE adds the energy spent on digestion, daily activity and exercise on top of BMR, giving a fuller picture of total daily calorie needs.

Why did my weight loss stall even though I am eating below my calculated TDEE?

This is common and does not necessarily mean the calculation was wrong. As weight drops, BMR falls, and sustained dieting can trigger further metabolic adaptation and a drop in incidental daily movement, both of which lower real-world TDEE below the original estimate. Recalculating periodically and double-checking calorie logging accuracy are the usual first steps.

المراجع

1. Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990.
2. National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner.
3. Centers for Disease Control and Prevention. Adult Activity: An Overview.
4. Centers for Disease Control and Prevention. How to Measure Physical Activity Intensity.