So basically, if you declare bread mass factor which is equal to mass of one cubic meter of bread over mass of one cubic meter of water, then divide it by 1000 and then multiply it by 2, which is average capacity of normal human stomach in liters, then multiply it by 7258 millions and then add this result to formula equal to obesity factor (which is an average number of additional liters a stomach of obese person can contain) times a fraction of obese population of the world in decimal number, you will get an average ammount of bread in kilograms needed to fill somach of each person on the planet