Weight Change from Energy Balance

This formula estimates how much body mass may change when a person accumulates a calorie deficit or surplus, using about 7700 kcal per kilogram of body fat. It comes from the rough energy content of stored adipose tissue: if you consistently eat less energy than you burn, the body must draw on stored fuel, and the reverse is true for a surplus. It is an approximation, because real body weight also shifts with water, glycogen, and changes in lean tissue, so it is best for rough planning rather than exact prediction.

Use this when estimating expected fat loss or gain from a tracked calorie deficit/surplus over days to months, such as in diet planning or sports nutrition. It is also useful for checking whether a proposed weight-change target is physically plausible from the stated energy balance.

• Treating the result as exact body-weight change instead of an approximation of fat change
• Using calories eaten in a day without subtracting energy burned, which is not a deficit
• Forgetting that a surplus gives weight gain and a deficit gives weight loss, so the sign matters