Weight loss is simple in principle — consume fewer calories than you expend — but the practical details determine whether you lose fat sustainably or spin your wheels for months. This guide walks through six evidence-based steps, each backed by a specific calculation so you always know where you stand.
Key Terms
- BMI — Body Mass Index: A screening index calculated as weight in kilograms divided by height in metres squared. It classifies weight status but does not measure body composition directly.
- TDEE — Total Daily Energy Expenditure: The total calories your body burns in 24 hours, accounting for resting metabolism, digestion, and all physical activity.
- BMR — Basal Metabolic Rate: The calories your body burns at complete rest to sustain vital functions — breathing, circulation, and cellular repair.
- Calorie Deficit: The state of consuming fewer calories than your TDEE, which forces the body to draw on stored fat for energy.
- Macronutrients: The three energy-providing nutrients — protein (4 kcal/g), carbohydrates (4 kcal/g), and fat (9 kcal/g) — that make up the bulk of any diet.
Step 1: Calculate Your BMI
Body Mass Index (BMI) gives you a fast, number-based picture of where you sit on the weight spectrum relative to your height. Use the BMI Calculator to compute your score instantly.
The formula: BMI = weight (kg) ÷ height (m)²
A person who weighs 80 kg and stands 1.75 m tall has a BMI of 80 ÷ (1.75 × 1.75) = 26.1.
Standard BMI categories:
| BMI Range | Classification |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
What your BMI number tells you — and what it does not. BMI is a population-level screening tool developed by statisticians, not clinicians. It is useful for identifying weight-related health risk at scale, but it has a well-documented limitation: it cannot distinguish fat mass from lean muscle mass. A 95 kg competitive weightlifter and a 95 kg sedentary office worker at the same height will produce identical BMI scores, even though their body composition and health risks are completely different. Athletes and individuals with high muscle mass should treat BMI as a rough indicator only and cross-reference with waist circumference or body fat percentage.
Despite its limitations, BMI remains the starting point for most weight loss frameworks because it correlates meaningfully with metabolic disease risk in non-athletic populations. Once you know your current BMI, use the Ideal Weight Calculator to find the weight range that puts you in the normal BMI band for your height. This gives you a concrete target rather than an abstract goal.
Step 2: Find Your TDEE
Your Total Daily Energy Expenditure (TDEE) is the single most important number in any weight loss plan — it tells you exactly how many calories you need each day to stay at your current weight. Eating below that number creates a deficit; eating above it causes gain. Use the TDEE Calculator to compute yours.
How TDEE is calculated:
TDEE = BMR × Activity Multiplier
Your Basal Metabolic Rate (BMR) is calculated from your age, sex, height, and weight using the Mifflin-St Jeor equation (the most validated formula for the general population):
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Activity multipliers:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1–3 days/week | 1.375 |
| Moderately active | Moderate exercise 3–5 days/week | 1.55 |
| Very active | Hard exercise 6–7 days/week | 1.725 |
| Extra active | Physical job or twice-daily training | 1.9 |
A worked example: A 35-year-old male, 175 cm tall, 75 kg, with moderate activity (gym three to four times per week).
BMR = (10 × 75) + (6.25 × 175) − (5 × 35) + 5 = 750 + 1,093.75 − 175 + 5 = 1,673.75 kcal/day
TDEE = 1,673.75 × 1.55 ≈ 2,594 kcal/day — call it 2,600 kcal/day for practical purposes.
This figure — approximately 2,600 kcal/day — is his maintenance level. Eating 2,600 kcal every day, he neither gains nor loses weight. Everything in the subsequent steps is calculated relative to this number.
One important caveat: activity multipliers are averages. People who stand all day at work, commute on foot, or have physically demanding hobbies often underestimate their activity level and select "sedentary," which results in a TDEE that is too low. When in doubt, choose a slightly higher activity level and then reduce based on real-world weight trends over two to four weeks.
Step 3: Set Your Calorie Deficit
With your TDEE established, you can engineer your calorie deficit — the gap between what you eat and what you burn. Use the Calorie Calculator to find your daily calorie target.
The fat-loss arithmetic: One kilogram of body fat stores approximately 7,700 kilocalories of energy. To lose that kilogram in one week, you would need a daily deficit of 7,700 ÷ 7 = 1,100 kcal. In practice, most people find this too aggressive to sustain — hunger becomes severe, energy crashes affect work and training, and the risk of muscle loss increases sharply.
Recommended deficit ranges:
| Weekly Fat Loss Target | Required Daily Deficit | Sustainability |
|---|---|---|
| 0.25 kg/week | ~275 kcal/day | Very sustainable, slow |
| 0.5 kg/week | ~500 kcal/day | Optimal for most people |
| 0.75 kg/week | ~750 kcal/day | Requires dietary discipline |
| 1.0 kg/week | ~1,100 kcal/day | Aggressive, risk of muscle loss |
Calorie floor — do not go below these minimums:
- Women: 1,200 kcal/day
- Men: 1,500 kcal/day
Eating below these thresholds deprives your body of the minimum energy needed to cover organ function and micronutrient intake from food. Research links very-low-calorie diets (below 800 kcal/day) with gallstone formation, muscle wasting, hair loss, and rebound weight gain once normal eating resumes.
For the example individual with a 2,600 kcal TDEE, a 500 kcal daily deficit sets his intake at 2,100 kcal/day. At this level, he can expect to lose roughly 0.5 kg of fat per week while maintaining adequate energy for training and daily life.
Step 4: Track Your Macros
Total calories determine whether you lose weight. Macronutrients determine what you lose — fat or muscle — and how you feel throughout the process. Use the Macro Calculator to set precise gram targets.
Why protein is non-negotiable during a deficit: When your body is in a calorie deficit, it turns to stored energy — ideally fat. However, without sufficient dietary protein, it will also break down muscle tissue for fuel. Preserving muscle matters for two reasons: muscle keeps your metabolism elevated, and it makes you look leaner at the same weight. The evidence-based protein target for weight loss is 1.6–2.2 g per kilogram of body weight per day. Athletes, older adults, and those on aggressive deficits should aim for the higher end.
Minimum fat intake: Dietary fat drops below adequate levels on many low-calorie diets, which disrupts the production of hormones including testosterone, oestrogen, and cortisol. The minimum is 0.5 g per kilogram of body weight per day. Healthy fat sources — nuts, olive oil, avocado, oily fish — should make up the bulk of this allowance.
Worked macro example for 75 kg, 2,100 kcal/day:
| Macro | Target | Calories |
|---|---|---|
| Protein | 135 g (1.8 g/kg) | 540 kcal |
| Fat | 60 g (0.8 g/kg) | 540 kcal |
| Carbohydrates | 255 g (remainder) | 1,020 kcal |
| Total | — | 2,100 kcal |
Carbohydrates fill the remainder once protein and fat floors are met. On days with heavy training, you can shift 20–30 g of fat into carbohydrates to fuel performance without changing total calorie intake.
A practical note on tracking accuracy: Studies show that people who self-report food intake underestimate their calories by an average of 20–40%. Weighing food with a kitchen scale rather than estimating portions is the single most effective way to close this gap, particularly in the first four to six weeks when you are learning portion sizes.
Step 5: Account for Exercise Calories
Physical activity adds to your total daily energy expenditure, which means it widens your deficit — or narrows it if you compensate by eating more. Use the Calories Burned Calculator to estimate your session output.
Approximate calorie burn by activity (for a 75 kg individual):
| Activity | Duration | Approximate Calorie Burn |
|---|---|---|
| Walking briskly | 30 min | 150–200 kcal |
| Jogging at 8 km/h | 30 min | 280–320 kcal |
| Cycling at moderate pace | 30 min | 240–280 kcal |
| Strength training (compound lifts) | 45 min | 200–400 kcal |
| Swimming laps | 30 min | 250–350 kcal |
| HIIT session | 20 min | 200–300 kcal |
The most common mistake with exercise calories: Fitness trackers, smartwatches, and cardio equipment displays routinely overestimate calorie burn by 20–30%. A treadmill that reports 400 kcal burned may reflect a true burn of 280–320 kcal. Eating back 100% of the displayed figure systematically closes your deficit and can bring fat loss to a complete stop.
A safer approach: account for 50–70% of estimated exercise calories when adjusting daily intake. Alternatively, set your TDEE using a realistic activity multiplier (which already incorporates your typical training load) and do not make calorie adjustments on individual workout days. The latter approach is simpler and less prone to overcorrection.
Strength training deserves a separate mention. The calorie burn during a weights session is modest compared to cardio, but the post-workout elevation in metabolic rate (the so-called "afterburn" effect, or excess post-exercise oxygen consumption) and the long-term increase in resting BMR from added muscle mass make it a powerful tool for fat loss over months rather than days.
Step 6: Review and Adjust Every 4 Weeks
Weight loss is not linear, and your plan should not be static. As you lose weight, your BMR decreases because there is less body mass to maintain. Your activity expenditure also decreases because moving a lighter body costs less energy. Without periodic recalibration, what started as a 500 kcal daily deficit gradually shrinks to 200 kcal — and progress stalls.
The four-week review protocol:
- Recalculate your TDEE at your current weight using the TDEE Calculator. Even a 4–5 kg reduction in body weight can lower TDEE by 80–150 kcal/day.
- Assess your weekly average weight trend. Weigh yourself every morning after using the toilet, before eating, and average the seven daily readings. This smooths out water retention fluctuations caused by sodium, carbohydrate intake, menstrual cycle, and stress.
- Diagnose the outcome:
- Losing 0.3–0.6 kg/week: your plan is working — make no changes.
- Losing less than 0.2 kg/week for two consecutive weeks: you have hit a plateau. Reduce intake by 100–150 kcal/day or add 30 minutes of low-intensity walking each day.
- Losing more than 0.8 kg/week consistently: increase intake by 100–150 kcal/day to slow the rate and reduce the risk of muscle loss.
- Update your macro targets via the Macro Calculator whenever your calorie target changes.
How to handle a weight loss plateau: Plateaus are a normal physiological response, not a personal failure. When the body is in a prolonged energy deficit, it reduces spontaneous movement (fidgeting, posture adjustments), lowers core body temperature slightly, and improves digestive efficiency — all of which reduce total energy expenditure. A two-week plateau is not evidence that your plan is broken; it is evidence that your body has adapted. The solution is a small additional reduction in intake, an increase in activity, or a brief "diet break" at maintenance calories for one to two weeks to allow hormones (particularly leptin) to recover before returning to the deficit.
Tracking beyond the scale: Body weight is one data point among many. Tape measure readings at the waist, hip, chest, and upper arm often show progress even during scale plateaus, particularly in people who are simultaneously building muscle through resistance training. Progress photos taken monthly under consistent lighting conditions are one of the most motivating forms of tracking because the visual change accumulates faster than the number on the scale suggests.
What to Do Next
Work through the six calculators in order:
- BMI Calculator — find out where you are starting
- Ideal Weight Calculator — set a concrete target weight
- TDEE Calculator — determine your maintenance calories
- Calorie Calculator — calculate your daily intake target
- Macro Calculator — set protein, fat, and carb gram targets
- Calories Burned Calculator — estimate exercise output
Sustainable fat loss averages 0.5 kg per week. Ten kilograms takes roughly 20 weeks at that pace — about five months of consistent effort. The six-step framework above removes guesswork from every stage of that journey.