What is the basic principle of weight loss?

• A. Energy intake less than energy expenditure
• B. Energy intake equals energy expenditure
• C. Energy intake greater than energy expenditure
• D. Energy intake has no effect on weight

Answer: (A)

Weight loss is driven by energy balance: calories consumed versus calories expended. When you take in fewer calories than your body uses for daily activities, digestion, and exercise, the body must tap into stored energy to cover the shortfall, usually drawing on fat stores and lowering body weight over time. You can create this deficit by eating less, increasing activity, or both. If calories in roughly equal calories out, weight remains stable. If calories in exceed calories out, weight tends to increase. Energy intake directly affects weight because the amount of energy you provide determines whether your body stores or uses energy.