BMR (Basal Metabolic Rate) is the number of calories your body needs to perform basic life-sustaining functions — breathing, circulation, cell production, and temperature regulation — while at complete rest. It accounts for roughly 60–70% of your total daily energy expenditure. Understanding your BMR helps you set a safe calorie floor for weight loss and avoid the metabolic slowdown that comes from eating too little.

TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor that accounts for all the energy you burn through movement, exercise, and even digesting food (the thermic effect of food). While BMR is your baseline at rest, TDEE represents your actual daily calorie burn. Eating at your TDEE maintains your current weight; eating below it leads to weight loss, and above it leads to weight gain.

The Mifflin-St Jeor equation is widely considered the most accurate BMR prediction formula for the general population, with studies showing it's accurate within about ±10% for most individuals. It outperforms older formulas like Harris-Benedict. That said, individual variations in muscle mass, body composition, and metabolism mean no formula is perfect — use these numbers as a starting point and adjust based on real-world results over 2–3 weeks.

A 500-calorie daily deficit typically leads to about 0.5 lb (0.23 kg) of weight loss per week, while a 750-calorie deficit yields roughly 1 lb (0.45 kg) per week. These are considered safe, sustainable rates. Avoid cutting below 1,200 cal/day for women or 1,500 cal/day for men, as extreme restriction can cause nutrient deficiencies, muscle loss, and metabolic adaptation that makes long-term weight loss harder.

Be honest and conservative when selecting your activity level. Most people overestimate their activity. Here's a quick guide:

• Sedentary: Desk job, minimal movement, no dedicated exercise
• Lightly Active: Light exercise or walking 1–3 times per week
• Moderately Active: Structured workouts 3–5 times per week
• Very Active: Intense daily exercise or a physically demanding job
• Extra Active: Competitive athlete or extremely physical occupation

If you're unsure, choose the lower option and adjust based on your weight trend after 2 weeks.

No, this is generally not recommended. Your BMR represents the energy needed for vital organ function. Consistently eating below your BMR can trigger metabolic adaptation — your body slows down its metabolic rate to conserve energy, making weight loss harder and weight regain more likely. It can also lead to muscle loss, fatigue, and nutrient deficiencies. Always aim to eat between your BMR and your TDEE for safe, sustainable fat loss.

Recalculate your calorie targets every 4–6 weeks or whenever your weight changes by 10 lbs (4–5 kg) or more. As you lose weight, your BMR naturally decreases (a smaller body requires less energy), so your calorie targets will need to be adjusted downward to continue progressing. This is a normal part of the weight loss journey — not a sign that something is wrong.

Yes, but it depends on your training experience. Beginners and those returning to training after a long break can often build muscle and lose fat simultaneously (called body recomposition), especially with a modest deficit, high protein intake (1.6–2.2g per kg of body weight), and consistent resistance training. For advanced lifters, muscle gain in a deficit is much harder — a maintenance or surplus is typically needed.

Several factors can cause a perceived plateau:

• Underestimating intake: Studies show people often underestimate calories by 20–40%. Use a food scale for accuracy.
• Overestimating activity: Your actual TDEE may be lower than calculated.
• Water retention: Sodium, carbs, hormones, and stress can mask fat loss on the scale.
• Metabolic adaptation: After prolonged dieting, your metabolism may have slowed.

Track for 2–3 weeks consistently before adjusting. If no change, reduce calories by another 100–200/day.

The most effective approach combines a food tracking app (like MyFitnessPal, Cronometer, or MacroFactor) with a digital food scale. Weighing your food in grams is far more accurate than estimating portions or using volume measurements. Track everything — including cooking oils, sauces, and beverages. After a few weeks of diligent tracking, you'll develop a much better intuitive sense of portion sizes and calorie content.