This Might Explain Why Diet Soda Drinkers Are Often Overweight

People who drink diet sodas over regular sodas are more likely to be overweight or obese, but scientists weren't sure why. The theories fell into two camps: one, something inherent to artificial sweeteners causes weight gain or two, diet sodas imply a diet and heavy people are more likely to be on one.

While we can't discount either quite yet, put down one more point for the first theory. A new study from the Weizmann Institute of Science in Israel reveals that artificial sweeteners may have a deleterious effect on our gut bacteria.

Researchers found that artificial sweeteners changed the composition of gut bacteria over time, which could explain why subjects became more glucose intolerant over time. Prolonged glucose intolerance leads to conditions like obesity and diabetes -- the very things that people drinking diet sodas are trying to avoid.

"Our relationship with our own individual mix of gut bacteria is a huge factor in determining how the food we eat affects us," said lead researcher Dr. Eran Elinav in a press release. "Especially intriguing is the link between use of artificial sweeteners -- through the bacteria in our guts -- to a tendency to develop the very disorders they were designed to prevent; this calls for reassessment of today's massive, unsupervised consumption of these substances."

To explore the connection between artificial sweeteners and gut bacteria, Elinav first conducted a series of experiments on mice. In the first, he added either saccharin, sucralose, or aspartame (common artificial sweeteners used in diet sodas and other foods) to the drinking water of mice pups. The control groups of mice pups got either plain water or sugared water.

After a week, he found that the mice who had been drinking artificially sweetened water developed significant glucose intolerance. Both groups given plain or sugared water had normal blood sugar levels. When Elinav subsequently gave the glucose intolerant mice an antibiotic to wipe out their gut bacteria, blood sugar returned to normal, proving the connection between gut bacteria and glucose intolerance.

Finally, to establish cause, Elinav transplanted feces (which contain a lot of gut bacteria) from saccharin-eating mice and sugar-eating mice to new groups of mice who hadn't eaten any sweetener at all. He found that the animals who had received feces from saccharine-eating mice developed glucose intolerance, while those who had received feces from sugar-eating mice did not.

But that's mice. What about humans? Elinav tested his theory on us, too. He examined data from 381 non-diabetic people, ages 30 to 56, who were part of an ongoing nutrition study that collects data on diets and gut bacteria. He found that those who reported eating more artificial sweeteners were more likely to be heavier, have larger waists and higher blood glucose levels when fasting. They were also more likely to have certain families of bacteria in common, too.

Elinav then completed a controlled experiment to compliment the observational data: He recruited seven healthy volunteers, ages 28-36, who normally avoid artificial sweeteners, and told them to consume the maximum amount of the FDA's acceptable daily intake of saccharine for a week (At 5 milligrams per kilogram of weight, that's like a 150-lb. person eating nine packets of Sweet 'n Low, according to Greatist). Throughout the week, researchers monitored their gut bacteria by examining their feces.

After seven days, four out of seven participants had begun to develop glucose intolerance. The evolution of their gut bacteria over the course of the week might explain why. The people who became glucose intolerant had "pronounced compositional changes" in their microbiota. Those changes could have been in response to the artificial sweeteners, suggest the study authors.

We have an estimated 100 trillion bacteria in our intestines, and they help us digest our food. But they don't just help break down our food; emerging research like Elinav's links imbalances in gut bacteria to conditions like obesity, Type 1 diabetes, celiac disease and Crohn's disease, just to name a few.

It could be that the key to managing or even preventing such illnesses is catering to that bacteria, and in the case of obesity and diabetes, that could mean avoiding artificial sweeteners.

"Artificial sweeteners were extensively introduced into our diets with the intention of reducing caloric intake and normalizing blood glucose levels without compromising the human 'sweet tooth,'" write the study authors. "Our findings suggest that [artificial sweeteners] may have directly contributed to enhancing the exact epidemic that they themselves were intended to fight."

Of course, this study doesn't mean that plunging headfirst into drinks with real sugar in them are any healthier -- the American Diabetes Association recommends avoiding sugary drinks like sweet tea, juice, soda and sports drinks altogether in order to prevent diabetes.

May we suggest a piece of fruit to satisfy that sweet tooth?

Arizona Raspberry Iced Tea
These recognizable-anywhere cans are bad news: They contain 23.5 ounces, nearly three times the suggested serving size for the tea inside. With 90 calories per 8 ounces, finishing an entire can adds up to almost 270.

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Starbucks Bottled Mocha Frappuccino
The 9.5-ounce Starbucks to go contains 180 calories.

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Jamba Juice Smoothies
Granted, Jamba Juice All Fruit smoothies are made with much better-for-you ingredients than a can of cola. However, it's still easy to mindlessly sip your calories when a 16-ounce size clocks in at least 210 calories.

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Minute Maid Lemonade
A 12-ounce can of the summer favorite clocks in at 150 calories, more than a can of Coke and the same as a can of Pepsi.

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Snapple Apple Fruit Drink
There are 100 calories in every 8 ounces of this fruity pick, but the bottle is deceiving, since it packs 16 ounces.

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Sunkist Orange Soda
There are 170 calories per 12-ounce can of this sweet drink.

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Dr. Pepper
A 12-ounce can clocks in at 150 calories, more than a can of Coke and the same as a can of Pepsi.

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Dunkin' Donuts Strawberry Coolatta
Even the small size of this frozen concoction from the coffee chain is a diet danger, with 230 calories in 16 ounces.

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Monster Energy Drink
There are only 100 calories in 8 ounces of this pick-me-up, but who only drinks half a can? The whole thing will set you back 200 calories.

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Nesquik Lowfat Chocolate Milk
An 8-ounce bottle of this sweet sip adds up to 170 calories. Beware of larger sizes that encourage bigger portions.

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Barq's Root Beer
Each 12-ounce can contains 160 calories.

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