People much smarter than you or I could even dream to be have been researching this for years . This is why we have the data that gives us calorie expenditure estimates for ageheightweightgender . They work great for most people . There will always be outliers , but this does not mean CICO is bunk . Instead , it means that some people have higher or lower than average expenditure . I lost a substantial amount of weight eating 1800 kcalday worth of pizza for about 6 months . This is why I can ' t just agree with your carbs obesity and CICO doesn ' t work ideas . There is more to it , but it doesn ' t mean the outcome changes . You put gas in your car , it uses it as fuel . That ' s a fact and no matter how complicated the combustion cycle may be , you can still estimate how much fuel you need to drive a certain distance with enough data . Same thing with bodies and food .