Most people know the basic principle of weight change:

• To lose weight → burn more energy than you consume
• To gain weight → consume more energy than you burn

Where many get stuck is understanding the “burn” side of the equation. That’s where Total Daily Energy Expenditure (TDEE) comes in—a framework that helps you visualise how your body actually uses energy each day. Research shows that once people understand their energy balance, weight management becomes far more predictable [1].

What TDEE Really Means

Your Total Daily Energy Expenditure (TDEE) is the total amount of energy your body uses in a day.
It is made up of four key components:

1. Basal Metabolic Rate (BMR) – energy used for essential functions at rest
2. Non-Exercise Activity Thermogenesis (NEAT) – incidental movement like walking, fidgeting, chores [2]
3. Exercise Activity Thermogenesis (EAT) – calories burned during structured workouts
4. Thermic Effect of Food (TEF) – energy used to digest and process food, typically ~10% of daily energy [3]

Your TDEE is influenced by age, muscle mass, movement levels, and lifestyle patterns [4–5].

How Food Fits Into the Equation

Calories from food represent energy in.
A typical Singaporean adult diet ranges from about 1,850–2,200 kcal/day, depending on food choices and portions [6].

This creates three broad possibilities:

• Weight gain → intake exceeds TDEE
• Weight loss → intake is consistently below TDEE
• Weight maintenance → intake matches TDEE

This process is not about willpower—it’s physiology [7].

How TDEE Can Be Calculated

There are several ways to estimate your TDEE, and all provide a usable starting point.

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1. Common TDEE Formulas

These formulas first estimate BMR (Basal Metabolic Rate), then multiply by an activity factor to calculate TDEE.

Activity Factors (used in all formulas)

• Sedentary (little/no exercise): × 1.2
• Lightly active (1–3 days/wk): × 1.375
• Moderately active (3–5 days/wk): × 1.55
• Very active (6–7 days/wk): × 1.725
• Extra active (hard training/physical job): × 1.9

(a) Mifflin–St Jeor Equation (Most Accurate for General Use)

Men:
BMR = 10 × weight (kg) + 6.25 × height (cm) – 5 × age + 5

Women:
BMR = 10 × weight (kg) + 6.25 × height (cm) – 5 × age – 161

TDEE = BMR × Activity Factor

(b) Harris–Benedict Equation (Older, Slightly Overestimates)

Men:
BMR = 66.47 + (13.75 × weight kg) + (5.003 × height cm) – (6.755 × age)

Women:
BMR = 655.1 + (9.563 × weight kg) + (1.850 × height cm) – (4.676 × age)

TDEE = BMR × Activity Factor

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(c) Katch–McArdle Equation (Best for Those Who Know Body Fat %)

Step 1: Lean Body Mass (LBM)
LBM = Body Weight × (1 – Body Fat %)

Step 2: BMR
BMR = 370 + (21.6 × LBM in kg)

Step 3: TDEE
TDEE = BMR × Activity Factor

2. Wearable Technology Estimates

Devices like Apple Watch, Garmin, Fitbit, and WHOOP estimate daily energy burn based on heart rate, movement, and user data.

Pros: convenient and real-time
Cons: can deviate by 10–30% depending on exercise type

Use device numbers as trend indicators, not precise measurements.

3. Reverse-Engineering From Real Data

This method uses your real intake and weight trends:

1. Track your calorie intake for 1–2 weeks
2. Track weight daily
3. If weight is stable → average intake ≈ TDEE
4. If weight shifts → adjust using ~7,700 kcal per 1 kg of fat change

This is the most accurate method long-term because it captures your actual lifestyle.

4. Lab Testing (Gold Standard, Rarely Needed)

• Indirect calorimetry – measures resting metabolic rate
• Doubly labelled water – measures true daily energy expenditure over weeks

These methods are precise but expensive and generally used for research.

Where Sustainable Weight Loss Begins

A 300–500 kcal deficit below TDEE is the most sustainable approach for fat loss. Research shows that moderate deficits are easier to maintain and support better long-term results [8].

Consistency matters more than perfection. Tracking—even briefly—helps build awareness. Excess body fat is linked to increased chronic health risks [9].

Do You Need to Track Forever?

No.
You only track long enough to learn the “energy cost” of your regular foods. Over time, estimating becomes second nature.

Daily fluctuations don’t matter—weekly trends do.
Overshooting by ±100 kcal is normal; overshooting by 300–500 kcal daily is what disrupts progress [10].

Your TDEE changes with weight, age, muscle mass, and activity, so revisit it every few months [4].

Three Tips for Beginners

1. Start With an Estimate, Not Perfection

Use a formula. Let your weekly results refine your TDEE.

2. Track the Big Things First

Start with:

• main meals
• snacks
• calorically dense items (oils, desserts, drinks)

You don’t need to track every crumb to see meaningful results.

3. Adjust Based on Weekly Trends

Weight fluctuates daily due to water and glycogen.
Weekly averages give a clearer picture of real change.

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References

1. Hall KD et al. (2012). Energy balance and its components: implications for body weight regulation. American Journal of Clinical Nutrition. PMID: 22434603

2. Levine JA (2007). Non-exercise activity thermogenesis (NEAT). Best Practice & Research: Clinical Endocrinology & Metabolism. PMID: 17697152

3. Westerterp KR (2004). Diet-induced thermogenesis. Nutrition & Metabolism. PMID: 15507147

4. Speakman JR (2003). Obesity: the integrated roles of environment and genetics. Proceedings of the Nutrition Society. PMID: 15284410

5. Heymsfield SB et al. (2014). Evolving concepts on adjusting resting energy expenditure for body size. American Journal of Clinical Nutrition. PMID: 22863371

6. Health Promotion Board Singapore (2023). Energy and nutrient intake guidelines for adults. Government publication (non-PMID).

7. Hall KD et al. (2011). Quantification of the effect of energy imbalance on body weight. The Lancet. PMID: 21872751

8. Franz MJ et al. (2007). Weight-loss outcomes from clinical trials with ≥1-year follow-up. Journal of the American Dietetic Association. PMID: 17904936

9. GBD 2015 Obesity Collaborators (2017). Health effects of overweight and obesity in 195 countries. New England Journal of Medicine. PMID: 28604169

10. Hall KD, Guo J (2017). Obesity energetics: body weight regulation and diet composition. Gastroenterology. PMID: 28193517