"Addiction" might be a tad dramatic seeing as how there isn't actually any hard evidence that caffeine is addictive, but we're willing to stake our reputation as Internet doctors that pretty much everybody reading this has had a liquid stimulant today. There are casual and hard-core caffeine users, but both can find themselves getting fatter by the day.
The casual drinkers disguise their stimulant in layers of crushed ice and whipped cream. This gets to be a problem when drinks like Starbucks' famous Frappuccino have around 500 calories per cup. Even worse, the human brain has a logical disconnect when it comes to liquid calories. That is to say, it doesn't acknowledge them at all.
So for instance, a personal pan pizza from Pizza Hut has 610 calories. Therefore, your Starbucks beverage is like a little pizza transformed into a little fruity coffee with training-wheels. The difference is that the pizza will make you feel full. The Frappuccino won't.
You, as an unsatisfied, horse-faced Frappuccino-drinker.
Then you've got the hardcore caffeine users, who prefer high-energy beverages with names like Rockstar and Monster and Red Bull and many other things the drinker will never actually resemble. They may also drink black coffee or espresso. The hardcore drinker just wants the quick energy rush.
Now, while those drinks don't have the pizza-scale calories of the Starbucks drink up there, it doesn't matter because Caffeine has so many inventive methods of fattening you up that we could've named this article "6 Ways Caffeine Is Making Your Ass Resemble A Pile Of Damp Towels."
The biggest thing caffeine does is jack your stress level through the roof, which steers your metabolism straight into "Survival/Conservation" mode. While it's doing that, it also increases your appetite, which makes you seek a whole pile of comfort foods to swallow in order to cope with that stress we just mentioned. And while it's doing that, caffeine will also be running around your body fucking with your hormones and raising your cholesterol and basically just being a complete dick.
What we're trying to say is that the only reason a can of Red Bull hasn't gained sentience and murdered your entire family is because doing that probably wouldn't make you any fatter.
All that careful, thrifty shopping you're doing isn't only making you fatter, but it's also probably wasting your money. You can bulk-shop in two different ways; you can either buy a single huge unit of a foodstuff (say, an eight-gallon tub of pretzels) or you can buy a whole bunch of single-serving packages (a pallet of 48 juiceboxes.)
What you're thinking at the time of purchase: "For the price of one trip to a restaurant, I can have a year's worth of pretzels and juiceboxes!" You then cart your purchases home and immediately start devouring them at twice the rate you would if you didn't have so damn much of them (according to a survey published in the Journal of Marketing Research).