Let's all agree for a moment that coffee is a drink that, if it were a song, would win about a million Grammys. But if you aren't up for something bitter in the morning or during the afternoon slump, diet soda can seem like a great way to get a little caffeine without packing on the pounds. But if you've been doing that and can't seem to keep your hand out of the office candy jar or off the break room muffins, science says you might want to think twice about that beverage habit.

More sweetener, more urge to munch

Scientists and physicians have raised concerns that drinking diet sodas could make people gain weight, although research studies on the topic have produced mixed results. Researchers at the University of Syney's Charles Perkins Centre, however, recently found that exposure to artificial sweeteners made animals chow down.

Lead researcher Associate Professor Greg Neely explains that what's happening with artificial sweeteners is part of a "conserved starvation response" that makes nutritious food taste better when you're starving. The brain is designed to give you a reward when you take in real calories from sugar to help you survive, essentially telling your body "This is the good stuff, grab more of that!" Artificial sweeteners, however, interfere with this process, eventually increasing how sweet real sugar seems to the brain. The sweeter the sugar seems, the bigger the reward response you get and the more motivated you become to scarf everything in sight.

"...We found that inside the brain's reward centers, sweet sensation is integrated with energy content," says Neely. "When sweetness versus energy is out of balance for a period of time, the brain recalibrates and increases total calories consumed...Chronic consumption of this artificial sweetener actually increases the sweet intensity of real nutritive sugar, and this then increases the animal's overall motivation to eat more food."

Long-term sweetener use trains the brain to be energy blind

Now, here's where it gets a little scary. Researchers Green and Murphy used brain scans to look at how the brains of chronic diet soda and non-diet soda drinkers reacted to drinks with either sugar or artificial sweetener. They found that the brains of the diet soda drinkers showed no real difference between the sugar- and artificially sweetened beverages, indicating that the typical reward system meant to keep caloric consumption at a good rate was no longer reliable. In essence, the brain loses the ability to figure out how many calories you're getting, getting the idea that nothing is sweet or giving you enough energy. This potentially could lead to feelings of constant hunger that lead to excessive consumption, which could translate to a roller coaster ride of blood sugar trouble, energy spikes and crashes and lost productivity. To top it off, Green and Murphy also found that the brains of the diet soda drinkers showed less activity in the caudate head. Decreased activity in that area of the brain has been linked to higher obesity risk.

An occasional diet soda likely isn't going to mess with you too much. But science shows that drinking them all the time can wreak havoc on your brain and potentially make you feel like you could eat a horse (and maybe a cow, too). If you've made sure that your calorie intake is appropriate given your activity level but still find yourself hungry to the point of distraction, double check how many diet soda cans or bottles litter your work area. It might be that switching to healthy alternatives, such as unsweetened tea or sparkling water, could tame the bear in your stomach.