A calorie deficit occurs when you consume fewer calories than your body burns. Since roughly 3,500 calories ≈ 0.45 kg (1 lb) of fat, creating a consistent daily deficit leads to gradual fat loss over time. For example, a 500-calorie daily deficit results in approximately 0.5 kg of fat loss per week.
0.5–1 kg per week is generally considered a safe and sustainable rate of weight loss. Losing weight too quickly can lead to muscle loss, nutrient deficiencies, and metabolic adaptation. A moderate, consistent deficit is the most effective long-term approach.
Moderate deficits (around 500 calories) combined with adequate protein intake (1.6–2.2g per kg of bodyweight) and resistance training significantly minimize muscle loss. Extreme deficits are more likely to cause muscle breakdown alongside fat loss.