The 3,500-calorie rule: origins and limitations
The 3,500 kcal/lb figure was popularised by Max Wishnofsky in a 1958 paper and became the most widely cited rule in weight management. It derives from the approximate energy density of human adipose tissue (~7,700 kcal/kg, which equals ~3,500 kcal/lb).
Modern research has shown the rule overestimates short-term weight loss because it ignores metabolic adaptation and the fact that not all lost weight is fat. Nonetheless, it remains a useful planning heuristic for setting realistic expectations over weeks to months.