Weight loss can feel complicated, but at its core it follows one principle: energy balance. Eat fewer calories than you burn and you lose weight; eat more and you gain. Everything else — diet styles, meal timing, 'fat-burning' foods — only matters insofar as it helps you hold that balance. This guide explains how to apply the principle safely and make it stick.
How many calories do you burn?
Your body burns calories even at rest to keep you alive — this is your basal metabolic rate (BMR), and it accounts for the majority of your daily burn. Add the energy used by digestion and daily activity and you get your total daily energy expenditure (TDEE), the number of calories you burn in a day. The BMR calculator and TDEE calculator estimate both from your height, weight, age and activity level. TDEE is the anchor for any weight plan.
The calorie deficit
To lose weight you need a calorie deficit — eating fewer calories than your TDEE. Roughly 7,700 calories equal one kilogram of body fat, so a daily deficit of about 500 calories produces around half a kilogram of loss per week, or 1,000 produces about a kilogram. The calorie deficit calculator turns a target deficit into an expected rate of loss so you can plan realistically rather than hoping.
A worked example
Suppose your TDEE is 2,200 calories. Eating 1,700 a day creates a 500-calorie deficit, predicting about 0.45 kg of loss a week, or roughly 2 kg a month. That is sustainable and protects muscle. Trying to lose faster by eating 1,200 might work briefly but usually backfires through hunger, fatigue and muscle loss. The maths rewards patience: a moderate deficit you can maintain for months beats an aggressive one you abandon in weeks.
Why plateaus happen
As you lose weight, your TDEE falls — a smaller body burns fewer calories, and your metabolism adapts slightly to the lower intake. So the deficit that once drove steady loss shrinks over time, and the scale stalls. This is normal, not failure. The fix is to recalculate your TDEE at your new weight and adjust your intake or activity, rather than slashing calories further, which only deepens fatigue.
Quality, not just quantity
Calories drive weight, but the makeup of your diet drives how you feel and whether you keep muscle rather than lose it. Getting enough protein is especially important in a deficit, because it preserves muscle and keeps you full. Balancing carbohydrates and fats around that protein base is largely personal preference. The macro split calculator turns your calorie target into grams of each macronutrient.
Why crash diets fail
Very low-calorie diets cause rapid early loss — mostly water and muscle, not just fat — but they are hard to sustain, slow your metabolism, and almost always end in rebound weight gain. Sustainable loss of about 0.5–1% of body weight per week protects muscle and is far more likely to stay off. The safe weight-loss calculator suggests a sensible weekly target for your weight.
Tracking that actually works
You cannot manage what you do not measure, but tracking only helps if it is honest and sustainable. The most common reason calorie counting 'fails' is underreporting — forgetting the oil a dish was cooked in, the handful of nuts, the sip of a sugary drink — which can hide hundreds of calories a day and explain a stubborn scale. Weighing food for a week or two recalibrates your eye for portions even if you stop later. If detailed logging feels overwhelming, simpler habits work too: filling half your plate with vegetables, prioritising protein, and not drinking your calories will create a deficit for most people without a spreadsheet. Whatever method you choose, weigh yourself under the same conditions and judge progress by the multi-week trend, since daily weight swings with water and food.
Move more, too
Exercise increases the calories you burn and improves health far beyond the scale — mood, sleep, heart health and insulin sensitivity all benefit. Importantly, much of your non-exercise movement (walking, chores, fidgeting) adds up too. Combining a modest calorie deficit with regular activity protects muscle and tends to last far longer than dieting alone. Estimate the calories an activity burns with the calorie calculator, build the habit gradually, and let consistency do the work.