Understanding Metabolism and Weight

Your total daily energy expenditure (TDEE) consists of four components. Basal Metabolic Rate (BMR) accounts for 60-70% of calories burned and represents the energy needed for basic organ function. The Thermic Effect of Food (TEF) is 10-15% and represents the energy used to digest meals. Physical Activity (PA) is 15-30% and includes structured exercise. Non-Exercise Activity Thermogenesis (NEAT) is 5-15% and includes fidgeting, standing, and walking.

When people say they have a "slow metabolism," they usually mean their BMR is lower than average. But BMR variations between individuals of the same size are typically only 100-300 calories per day.

Muscle mass is the biggest factor you can control. Each kilogram of muscle burns approximately 13 calories per day at rest. While this sounds small, adding 3 kg of muscle increases daily burn by ~40 calories — equivalent to losing 2 kg of fat per year with no other changes.

Age reduces metabolism by approximately 2-3% per decade after age 20, primarily due to muscle loss. Hormonal changes, especially menopause in women and declining testosterone in men, also reduce metabolic rate.

When you lose weight, your metabolism slows down. This is called adaptive thermogenesis. For every kilogram of weight lost, BMR drops by approximately 20-25 calories. Lose 10 kg, and your body burns 200-250 fewer calories daily.

This adaptation is partly why weight loss plateaus occur. It is also why maintaining weight loss is harder than losing it. The body defends its highest weight as a set point.

Build and maintain muscle through resistance training. This is the single most effective way to preserve metabolic rate during weight loss. Eat adequate protein — the thermic effect of protein is 20-30%, compared to 5-10% for carbs and fats.

Increase NEAT by walking more, standing instead of sitting, and taking the stairs. These small movements add up to hundreds of calories daily. Get enough sleep — sleep deprivation reduces BMR and increases hunger hormones.