Fattening of America - A Conspiracy

As if "want us to super size that for you" wasn't enough of a reason to think there was some kind of conspiracy to fatten up America I've now found that several local sandwich chains now charge you more if you want less food. When you approach the register for your sandwich and small drink you are asked if you don't want to "make it a combo" which includes a bag of chips. When you decline the sales clerk quite helpfully will let you know that declining the combo, i.e. foregoing the chips, will increase the cost of your meal by 10%. What kind of business model is that???

I guess the idea is that if they fatten us up and stretch our stomachs we will buy more later? But what about the premature deaths of customers? Or is Frito-Lay giving kickbacks?