BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to maintain basic functions like breathing, circulation, and cell production. It matters for weight loss because it forms the foundation of your total daily energy expenditure (TDEE). To lose weight, you need to consume fewer calories than your TDEE. Knowing your BMR prevents you from cutting calories too aggressively, which can slow your metabolism and cause muscle loss.

To lose weight, you need a calorie deficit — consuming fewer calories than you burn. A deficit of 500 calories per day leads to approximately 0.45 kg (1 lb) of fat loss per week. A 1,000 calorie daily deficit targets around 0.9 kg (2 lbs) per week. Most health guidelines recommend not going below 1,200 calories/day for women or 1,500 calories/day for men without medical supervision, as very low intake can lead to nutrient deficiencies and metabolic slowdown.

BMR is the calories your body burns at complete rest — if you stayed in bed all day. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for your daily movement and exercise. TDEE is the actual number of calories you burn in a typical day, and it’s what you should compare your food intake against when trying to lose weight. Your TDEE will always be higher than your BMR.

The Mifflin-St Jeor formula (developed in 1990) is widely considered the most accurate BMR formula for healthy adults. The formulas are: Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161. It is preferred over the older Harris-Benedict formula because it was validated against more modern populations and tends to be more accurate across a wider range of body types.

Most health authorities recommend losing 0.5–1 kg (1–2 lbs) per week as a safe and sustainable rate. This requires a daily calorie deficit of 500–1,000 calories. Losing weight faster than this can cause muscle loss, nutrient deficiencies, and metabolic adaptation — where your body lowers its BMR to compensate. Slow, steady weight loss preserves muscle mass, maintains energy levels, and is far more likely to be maintained long-term.

Yes, significantly. Exercise helps with weight loss in several ways beyond direct calorie burn: it increases muscle mass which raises your BMR over time; it improves insulin sensitivity making fat storage less likely; it reduces appetite hormones in many people; and it raises your activity multiplier, meaning your TDEE is higher without needing to change your diet. Resistance training is particularly valuable because muscle tissue burns more calories at rest than fat tissue, creating a compounding benefit over time.

Macros (macronutrients) are protein, carbohydrates, and fat — the three sources of calories in food. For weight loss, protein is the most important macro to prioritise: it preserves muscle while in a calorie deficit, increases satiety (keeping you fuller longer), and has the highest thermic effect (your body burns more calories digesting it). A general guideline for weight loss is 1.6–2.2 g of protein per kg of bodyweight, with the remaining calories split between carbs and fats according to personal preference.

As you lose weight, your BMR decreases because a lighter body requires fewer calories to maintain itself. This is completely normal. Additionally, your body may undergo metabolic adaptation — reducing non-exercise activity (fidgeting, posture changes) and lowering hormone levels like leptin and thyroid hormones. To continue losing weight, you’ll need to periodically recalculate your TDEE based on your new lower weight, or increase activity. Diet breaks of 1–2 weeks at maintenance calories can help reset hormones and prevent plateaus.