Appetite and metabolism is much more complicated than a thermodynamics problem. A calorie deficit implies knowledge of metabolic rate which can be highly varia

Appetite and metabolism is much more complicated than a thermodynamics problem. A calorie deficit implies knowledge of metabolic rate which can be highly variable. While calories in can be trivially counted, calories out needs to be calculated and cannot assume a significant level of accuracy. Regardless, the problem with solving the obesity epidemic isn’t that people can’t lose weight, but is keeping weight off after reaching a goal weight.