Which statement best defines energy balance and its relation to weight change?

• A. Energy balance is the ratio of calories from fat to calories from carbohydrate.
• B. Energy balance equals energy expenditure minus intake; positive balance leads to weight loss.
• C. Energy balance is unrelated to weight change.
• D. Energy balance equals energy intake minus expenditure; positive balance leads to weight gain, negative to weight loss.

Answer: (D)

Energy balance is about calories in versus calories out. It means the amount you eat (energy intake) minus the amount you burn (energy expenditure) determines how your body’s energy stores change. If you take in more energy than you burn (positive balance), over time your body stores the excess as fat, leading to weight gain. If you burn more than you take in (negative balance), your body uses stored energy and you lose weight. When intake and expenditure are about equal, your weight stays stable.

The other statements don’t fit because the ratio of fat to carbohydrate calories doesn’t define energy balance, and the equation should be intake minus expenditure, not the other way around. Also, energy balance is directly related to weight change, not unrelated.