Dear Science,
I have at least a few friends who, as part of trying to lose weight, drink diet soda constantly. Even after a few of them shifted from corn-syrup-packed regular soda to diet, their weight doesn’t seem to budge. In fact, the fattest people I know happen to be the biggest diet soda drinkers. I think it’s connected, drinking diet soda and being fat. Back me up, Science! Does drinking diet soda make you fat?
Correlating Coke Hater
You’re on to something: At least a few studies—including some recent data presented at a scientific conference on diabetes—seem to connect diet soda consumption with metabolic syndrome (the combo of high blood pressure, high blood sugar, obesity, and generally a higher risk for everything you don’t want).
One of the first really solid hints of this connection came from a carefully done bit of research by University of Minnesota scientists, published in 2008 in the journal Circulation. This prospective study (which carefully followed a group of people over decades, checking in every three years) used a questionnaire about dietary habits to connect specific foods with the development of metabolic syndrome. As most of us would expect (and probably already know), people who ate a lot of meat and fried foods were much more likely to develop the syndrome. Intriguingly, drinking diet soda was about as associated with developing metabolic syndrome as eating fatty foods and mounds of meat. In contrast, the consumption of sugary drinks (sweetened by corn syrup or cane sugar) was not associated either way. (Consuming dairy was beneficial, protecting against metabolic syndrome.)
The more recent work—from a group at the University of Texas, San Antonio—was an eight-year prospective study attempting to connect the consumption of certain foods with the development of diabetes. The results were similar, with the consumption of soft drinks strongly associated with the eventual development of diabetes. Fascinatingly, almost all of this increased risk came from those who drank diet soft drinks—not corn-syrup- or cane-sugar-sweetened ones. The risk wasn’t tiny: The study found a 41 percent increase of being overweight for each can of diet soft drink consumed (on average) per day.
Why would diet soft drinks—which provide no calories—be more likely to cause metabolic syndrome (aka an unhealthy obese person) than sugar-sweetened soft drinks? (To be clear here, sugary soft drinks are no health food. It’s just that diet soft drinks are nearly twice as risky for diabetes.) Nobody quite knows yet, but the speculation is interesting. Perhaps artificial sweeteners make us less sensitive to real sweetness—and thus we eat more. Or perhaps the artificial sweeteners trigger our bodies to release insulin, causing our blood sugar to drop, which makes us crave bigger meals later. The eventual answer is going to be enthralling.
Sweetly Yours,
Science
Send your science questions to
dearscience@thestranger.com
It may be that the you have the implied causation backwards. Given some doctor’s advice and the implication of “diet” in diet soda, it may be that syndrome “causes” diet soda, not the other way around.
How about this hypothesis: Diet soda is fucking terrible. People with poor diet self-control make a minor concession to health by drinking too much diet soda instead of too much regular soda. Now that they’ve made that healthy but essentially inconsequential switch, they consider the “eating habits improvement project” done and continue to eat too much other unhealthy crap. A normal person would just start drinking less soda (because diet soda is fucking terrible, the normal person would drink more water, or tea, or whatever); this is a self-control issue that likely carries over into other areas of the normal persons diet, so that person also tends to not be fat.
In essence, the consumption of diet soda and being fat are separate but related indicators of a person with limited self-control when it comes to eating habits.
I am idly wondering, ctmcmull, whom you consider dumber, fat people with their oh so stupid habits or scientists, who in your worldview never thought of taking other dietary habits into account.
Only, they did. Try reading the above article again, and go for reading comprehension this time instead of being blinded by feelings of superiority.
Ctmcmull can no longer feel superior to black people or Jews so now he looks down on fat people (and probably smokers too).
Yes, ctmcmull’s racist views are becoming a nuissance. Give it up, you bully.
ctmcmull’s racist rant must have added an extra ‘s’ to nuisance for me. Damn you ctmcmull!
Ok, so fatty foods are bad, dairy is good. So where is cheese on this continuum? Please tell me I can switch to an all-cheese diet tomorrow.
jfljoe: damn your insouciance! But really, I mostly feel superior to religious people, which really takes very little effort.
Correct me if I’m wrong, but I always thought that it’s a well-established fact that sweeteners directly cause the release of Insulin. Is this actually merely a speculation at this point? I’d be very grateful for an answer, Mr. Golob or anyone qualified…
@1: Maybe you said it too “mean” but I think you have a point. These studies show correlation, not causation. It seems quite likely that fatter people, or people with diabetes, would drink more diet soda. But this does not prove that these sodas cause fatness or diabetes–quite the opposite. Teasing out correlation from causation is one of the most difficult problems in experimental science, and I think in this case there is ample room for skepticism.
@9: It is a well-supported hypothesis, but as far as I know it hasn’t been proven, yet.
@7: All hail TV Dinner!!!
I’m stocking up on frozen foods tomorrow!!!
Diet sodas are also known to empty from the stomach faster than regular, so any benefits of feeling full from them go away faster. Because of this, diet soda as a mixer will also get alcohol into your blood stream faster than regular soda.
@11 Thx for the answer, but I still wonder: How difficult could it be to test this hypothesis? Have participants divided into three groups, give a drink of regular soda to one, diet soda to the next and water to the third, compare their blood sugar and insulin levels after…wouldn’t that do the trick?
A prospective study starts before the disease (in this case metabolic syndrome), and tests if those who start from the same point but have different variables (diet soda drinking vs. regular soda drinking) have different results. In this case, if you drink diet soda, you are more likely to get metabolic syndrome than someone who drinks sugar soda. Not having the studies in front of me, I make the assumption (always excitingly dangerous) that the researchers started with people who matched to begin with, that they had similar eating habits and weights.
Insulin is not the be all and end all of weight or metabolic syndrome, ghrelin and another hormone (don’t recall the name offhand) are also important; as is a tendency towards inflammation. Sleep is also very important, if you get too little sleep you will get fatter and more likely to be ill than if you get enough sleep.
Another hypothesis about the possible (and obesity & thus metabolic syndrome-promoting effects) comes from Seth Roberts, PhD (formerly tenured UC Berkeley psychology professor) and author of the Shangri-La Diet. He believes that diet soda entails an experienced association of sweetness and no-calories that raises the body’s set point for weight. The book is not hard to understand and a web search will uncover various summaries of his basic ideas and framework. The flip side is his regimen for weight loss, the opposite of diet soda, near-tasteless oil or near-tasteless dextrose solution: this is what he believes lowers the body’s set point for weight.
Brunobar has a point. While reading this blurb I was reminded of a childhood friend’s mother who was obese but drank diet to make herself feel better. And lots of people order big burgers with a diet coke. Previous research (sorry, I don’t have a citation. It was discussed in the March New Yorker) has seen metabolic signals appearing within hours of consuming different foods, so it could be possible to construct control groups to test the idea. The results would be restricted to short-term indicators but would advance the inquiry.