You are assuming that the underreporting will be uniform. In reality people may be underrporting things they are embarrassed about and maybe even overreporting the opposite.
This is a flaw in the data that is much harder to account for.
Why would that be a problem for reporting relative results if everyone is under-reporting things they're embarrassed about and over-reporting the opposite?
Different people are embarrassed by different things. A frat student's probably going to overstate their alcohol consumption, a Morman understate.
People with bigger appetites underestimate their food consumption, people with smaller appetites overstate.
Not to mention the degree of over/under statement will vary wildly. "A big meal" might be 300 calories for somebody with an eating disorder, or 3000+ for somebody on the opposite end of the spectrum.
BoxFour|1 year ago
OkayPhysicist|1 year ago
People with bigger appetites underestimate their food consumption, people with smaller appetites overstate.
Not to mention the degree of over/under statement will vary wildly. "A big meal" might be 300 calories for somebody with an eating disorder, or 3000+ for somebody on the opposite end of the spectrum.