I don’t know anything about a random guy you work with. All I know is that being “sick” is your body’s appropriate response to toxin exposure. If he’s constantly poisoning himself, then no. He’s not “healthier” than you (as far as I know what you’re exposing yourself to). Not being “sick” does not mean “healthy”. It means “your body is not currently in the process of detoxifying itself”. Detoxification requires nutritional inputs like minerals and amino acids. If you run out (or your organs are impaired), then your detox abilities are stunted and you will feel “sick” less often.