No, food is assigned at the beginning of the 'off turn' whereas hammers are assigned at the end. So at the end of your turn, computer sees you have food overflow and assigns the new citizen. Where does the citizen go? If it's a food tile then the food has already been counted, so it adds nothing for the turn. but if it's hammers, they haven't been counted yet, so the new citizen will add to the hammers for this turn - win! So micromanagers will set focus to production, but lock the food tiles asap with their new citizens. i don't know when gold or other things are counted though.
Also, for unhapiness issues, food is done by city going down the city list, so if you're on 0 hapiness with 3 cities with 1 turn to the new citizen, the first city on the list will get the new pop at happy rates, but then the other 2 will get their food on unhappy rates. great people generation works in a similar way, so you can multipop within cities but not across cities.