Here’s the big picture: If you eat zero calorie “diet” products, you can be left with more than zero calories. In fact, a study from theDepartment of Psychological Sciences and Ingestive Behavior at Purdue University looked at all the reviews of all the studies on artificial sweeteners over the past 40 years. They’re finding that consumption of these synthetic sweeteners can induce metabolic derangement and because of this: “… accumulating evidence suggests that frequent consumers of these sugar substitutes may also be at increased risk of excessive weight gain, metabolic syndrome, type 2 diabetes, and cardiovascular disease.”
In other words, when you drink diet drinks and eat diet products that contain synthetic ingredients your body does not recognize or know how to process, this kind of physiological derangement follows, which can result in:
Weight gain. Even if you are of normal weight to begin with, according to the San Antonio Heart Study, the risk of becoming overweight and even obese increases for those who drink artificially sweetened beverages.
Diabetes. Even if you only drink one diet drink, you’re more likely to get type 2 diabetes, and if you drink a lot of them your risk than twice as likely to develop diabetes.
Heart disease. The Nurses Health Study has shown that drinking artificially sweetened beverages as associated with an increased risk of coronary heart disease.
Metabolic Syndrome.The American Medical Association defines “metabolic syndrome” as a group of symptoms that all occur together, including a high waist circumference + high triglycerides + low HDL (“good”) cholesterol + high blood pressure + high blood sugar. All of that, that entire metabolic disaster, is from 17 to 100 percent more likely to happen when you consume synthetic zero calorie sweeteners!
The “Why” of it all
One theory is that artificial sweeteners uncouple the taste of sweet things from the normal calories that come with that sweet thing. In this way, whenever you do eat something with sugar – or even something that breaks down into sugar – your body has a reduced ability to metabolize it. This can lead to the nest of problems, listed above.
Another theory is that any invented synthetic that your body has never seen before will be processed by your body in unpredictable ways leading to the next of problems, listed above.
But is “the reason why” important, really? I know it’s very important for academics, doing academic work, in academia. But for me, and you, and my mom, living a normal life in the normal crazy-busy world, the reason why isn’t really necessary! Think of it like this: Astrophysicists are still working on understanding the equations to explain why gravity pulls things toward the earth. But you don’t have to wait on them to iron things out to know that jumping off a building generally results in negative consequences.
In the same way, just knowing that the consumption of artificially sweetened diet drinks do, in fact, increase your risk being overweight, obese, hypertensive, with heart disease, and have the closet of physiological derangements know as Metabolic Syndrome should convince you to choose something else, something real.
Does this mean you should start drinking regular sodas with piles and piles of sugar in them? Of course not. But it does disabuse us of the fantasy that sodas are okay if the marketing tells you that it is has zero calories, and therefore zero consequences.
 Swithers SE., Artificial sweeteners produce the counterintuitive effect of inducing metabolic derangements. Trends Endocrinol Metab. 2013 Jul 3.  Fowler, S.P. et al. Fueling the obesity epidemic? Artificially sweetened beverage use and long-term weight gain. Obesity (Silver Spring) (2008), 16, 1894–1900  Romaguera, D. et al. Consumption of sweet beverages and type 2 diabetes incidence in European adults: results from EPIC-InterAct. Diabetologia (2013) 56, 1520–1530  de Koning, L. et al. Sugar-sweetened and artificially sweetened beverage consumption and risk of type 2 diabetes in men. Am. J. Clin. Nutr. (2011) 93, 1321–1327  Fung, T.T. et al. Sweetened beverage consumption and risk of coronary heart disease in women. (2009) Am. J. Clin. Nutr. 89, 1037–1042