This week, diet soda was in the news again, as a small group has filed lawsuits against the three major soft drink producers claiming that diet sodas lead to weight gain and that promoting them as diet aids is false advertising. I’m personally not a fan of litigious moves that decrease personal responsibility, but I am a huge fan of the point that this group is trying to make: diet sodas aren’t good for you! Also, they don’t help you to lose weight or to avoid gaining it. On a nearly daily basis with patients I make the statement, “If you do nothing after this appointment but stop using artificial sweeteners, we will make great strides.” In fact, it is more important for me to get a person to stop diet soda than it is to have a regular soda drinker quit their bad habit, especially if they are losing the battle against weight. If you have been under the impression that diet soda is a good choice, don’t be too hard on yourself. Both the American Heart Association and the American Diabetes Association have approved and recommended them at one time based on old nutritional assumptions. At this point, however, we get at least a few studies per year which confirm the artificial sweeteners typically don’t lead to weight loss, usually cause people to gain weight, and they might even lead to increased disease.
Much of the confusion with diet soda stems from our perpetual resistance to think of weight gain and weight loss as being more complicated than “calories in versus calories out.” This mantra has been repeated for decades, and thus, common sense led us to believe that a beverage with no calories would be a healthy choice especially in regards to controlling weight. Instead we have seen the opposite. In a study at the University of Texas in 2013, researchers followed diet-soda drinkers for a decade and found that they had a 70% greater increase in waist circumference compared to non-drinkers. Researchers at Purdue University similarly found that artificial sugar substitutes increased appetite and promoted weight gain. An article in JAMA Pediatrics focused on pregnant women and published that in a group of 3,000 births, women who used artificial sweeteners were twice as likely to have overweight babies.
You might assume that most of these studies are following people who otherwise don’t make great choices. We’ve all heard the joke about ordering a large fries and then a diet coke. And although this could be part of the causation, there are plenty of studies that have adjusted for these possible differences. In the Journal of the American Geriatrics Society, a study of about 750 people over the age of sixty-five highlighted that people who drank diet soda gained almost triple the abdominal fat over nine years as those who didn’t drink diet soda. The results confirmed that drinking diet soda was extremely predictive of abdominal-fat gain, even after the researchers adjusted for factors like diabetes, smoking, and levels of physical activity. People who didn’t drink diet soda gained about 0.8 inches around their waists over nine years, but people who drank diet soda daily gained 3.2 inches! Abdominal weight is directly linked to metabolic syndrome, which is probably why an additional study showed a 36% increase in metabolic syndrome (an association of weight gain, high blood pressure, high fasting glucose and high cholesterol) in diet soda drinkers versus non-drinkers.
At this point, considering the surmounting evidence, it seems unlikely that we will ever return to the idea of thinking that sugar substitutes might help you to avoid weight gain, but the unanswered question remains exactly how could this be? If you avoid calories, why wouldn’t you be the one with the smaller waist in 10 years?
The reason for our seemingly oxymoronic response to artificial substitutes likely has to do with our physiological response to sweet taste. Our entire process of both digestion and energy metabolism begins with out taste buds, and many experts believe that a sweet taste begins a cascade in our brains preparing for an influx of calories. Your pancreas is then stimulated to release insulin to process those calories. Insulin’s primary function is to pair with glucose (a part of sugar that the body assumes triggered the sweet taste) and transport it into cells to produce energy. But, remember you didn’t actually consume any glucose, so there isn’t anything to process. It has been shown that people who consume sucralose (today’s most common artificial sweetener) can release 20% more insulin compared to those who consume water. The question is, what does this extra insulin do if it doesn’t have sugar to process? Well, for one, it probably makes you hungrier, and some studies have confirmed that diet soda drinkers are more likely to consume extra calories or crave more actual sugar. But even more ominously, the increase insulin also likely causes you to store fat. This link goes back all the way to our DNA and our long-standing interpretation in our brains that if we have extra insulin, we must not be getting enough glucose; in other words, our brains think we could be facing a famine, and we prepare for that famine by storing fat. Hence, increased insulin, increased abdominal weight gain, then metabolic syndrome, which leads to increased insulin resistance, which results in even more insulin in the bloodstream . . . more abdominal weight gain. . . and you get the picture.
And unfortunately, weight gain is just the beginning of questions of disease related to artificial sweetener consumption. Sweeteners have been linked to headaches, myalgias, and lowered immunity. Furthermore, sodas, both diet and regular, are detrimental to bone health and bone degradation continues to be a substantial problem in this country. I’ve focused on diet sodas in this article because it is the most common way that people consume artificial sweeteners, but the same effects would hold true regardless of where you are consuming your sweeteners. Sweeteners will often be found in foods that claim to be “light,” or obviously that claim to be “diet.” Common types of artificial sweeteners include aspartame, saccharin, and now, most commonly, sucralose (Splenda). Sucralose is the most difficult to pick out on abels, as it is often only listed in the fine print of the ingredient list, and it is very close to the word for actual sugar, sucrose.
Although I encourage you to avoid all artificial sweeteners, this doesn’t mean that I would necessarily have you consume sugar instead. Certainly avoid regular soda as well and high fructose corn syrup has also been linked to extra weight gain and disease. If you desire an occasional soda, pick one with real sugar, but as in all sugar consumption, moderation is the key, and avoidance if you are diabetic.
You might assume also that you are in the clear if you are using Stevia or other natural sugar substitutes, but we don’t have any reason to think this is true. Remember that the cascade of events that led to increased weight gain all began with a sweet taste that was not followed with glucose intake. We should expect increased insulin and more efficient fat storage with any non-caloric sweet taste including stevia and agave.
It’s always disappointing to learn that something we might think of as a guilt-free treat might be worse for us than we thought, and it is even more disappointing that we were ever led astray in thinking that sugar substitutes were a good choice. But in the end, we are back in the same place we usually end up when we are talking nutrition: eat mostly whole, real foods, lots of fruits and veggies, lean meats, whole grains . . . and real, but limited, sugar, and you’ll be on the right track.
Stay healthy & be well!
-Amy Whittington, NMD