Black, green and white teas (hot or on ice) can help get you through an afternoon slump. All three varieties (though not herbal teas) contain a compound called L-theanine, which studies have shown improves attention when consumed along with caffeine, another component of tea. What’s more, the diet soda you’re drinking to save calories may actually be hindering your weight loss. In one study from the University of Texas Health Center, scientists found that for every diet soda consumed per day, the risk of being overweight or obese increases by 41 percent. Researchers speculate that the artificial sweeteners in diet drinks throw off your ability to regulate calorie intake.