Energy balance

Energy balance is the relationship between calories consumed and calories burned: weight stays stable when the two roughly match.^{1International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 464.} Eating less than is burned creates a negative energy balance, or calorie deficit, and weight falls; eating more creates a positive balance, or calorie surplus, and weight rises.^{1International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 464.} A deficit also shifts the body’s signaling toward breakdown, affecting how much muscle a client can build.^{2Schoenfeld, Science and Development of Muscle Hypertrophy, 2nd ed., p. 219.}

For fat loss, the NSCA advises trainers to keep clients focused on this principle: a diet produces weight loss only if it creates a negative energy balance.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 132.}

In practice

• Intake and expenditure affect each other.^{4Norton and Baxter, The Complete Reverse Dieting Guide, p. 13.} Eating less slows expenditure over time, so an initial deficit can become maintenance; overfeeding can raise expenditure.^{4Norton and Baxter, The Complete Reverse Dieting Guide, p. 13.}
• A stalled scale on a low reported intake doesn’t disprove energy balance.^{4Norton and Baxter, The Complete Reverse Dieting Guide, p. 13.} Norton and Baxter note that underreporting is common, while a client who tracks carefully and still doesn’t lose most likely has low expenditure.^{4Norton and Baxter, The Complete Reverse Dieting Guide, p. 13.}
• Body weight is an estimate of energy balance, not a precise readout.^{5Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 65.} The “3,500-calorie rule” is a simplification: muscle holds far fewer calories per pound than fat, so the numbers rarely line up exactly.^{5Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 65.}
• Judge a diet by the foods it includes and excludes, since its weight-loss claims still depend on creating a deficit.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 132.}