Sweet Obesity

Research Blogging / by Dave Munger /

As obesity rates soar, Americans are consuming more low-calorie artificial sweeteners. But do artificial sweeteners actually help people lose weight?

When I first moved to the southern US 15 years ago, I was startled at the extent to which sugar was a part of the culture. The drink of choice was “tea”—which meant not a delicate, hot, English beverage served in tiny cups, but an iced, syrupy concoction in giant plastic tumblers with endless free refills. I was even more surprised to see how sweet tea was made: by infusing the still-hot tea with sugar by the kilo, then chilling over ice. Southern grandmothers were using a basic principle of chemistry—supersaturation—to create a sweeter tea than would be possible if the sugar was added cold.

Back then, it was unusual to get free refills on soft drinks at restaurants in most of the country, but the practice was ubiquitous in the South. Now offering free soft drink refills has spread across the nation. At the same time, and also originating mostly in the South, the portion of obese Americans has increased at an alarming rate. In 1985, no state had an obesity rate above 15 percent. In 2008, none were below 15 percent, and only Colorado could boast that fewer than 20 percent of its citizens were obese. Six states now have an obesity rate higher than 30 percent.

Could cheap, sugary soft drinks really be at the root of the obesity crisis in America? And if so, isn’t switching to artificially sweetened “diet” soda the obvious answer? Travis Saunders, an obesity researcher and ResearchBlogging.org health editor who blogs at Obesity Panacea, can at least answer the first question: The increase in consumption of sugars, especially high-fructose corn syrup, has marched in lock-step with the rise in obesity in the US over the past 30 years. He cites research suggesting that sugar actually disrupts the metabolism and makes you hungrier.

Saunders says an August report from the American Heart Association (AHA) made it quite clear that excessive sugar consumption is dangerous, and he argues that sugar should be seen as a toxic substance. But how much is too much? The new AHA guidelines suggest limiting added sugar to no more than half of discretionary calories—calories consumed after basic nutritional needs are met. For the average male, Saunders says, this works out to about 150 calories per day: one can of Coke, or one candy bar. No free refills.

Again, the answer seems obvious: Just switch to diet drinks. They taste about the same, but with no sugar and no calories. Not so fast, says BikeMonkey, an anonymous biomedical researcher and former bike racer who blogs at DrugMonkey. BikeMonkey cites a 2008 study published in Behavioral Neuroscience where rats were given either sugar-sweetened or artificially sweetened yogurt in addition to their usual diet of rat chow. The rats who ate artificial sweeteners gained significantly more weight over five weeks than the rats who had sugar-sweetened yogurt.

In a second experiment, some rats were regularly fed saccharin while others were fed sugar. When the rats were given a pre-meal snack of the low-sugar, high-protein nutrition shake Ensure, the saccharin-trained rats went on to eat more rat chow than the sugar-trained rats. So it seems that consuming sugar-free foods and drinks may just lead to more eating later on.

Many of the commenters on BikeMonkey’s post wondered if these results would extend to humans, offering their own anecdotal reports of sugar-free sweeteners helping them lose weight. Yoni Freedhof, an Ottawa-based obesity doctor, cites a July study from New Zealand in the International Journal of Obesity that looked at dieters who were able to lose 10 percent of their weight and keep it off long term. As you might expect, these people had to work much harder to maintain weight loss than people who never lost weight. The dieters consumed many reduced-fat and reduced-sugar foods, and they drank three times more artificially sweetened beverages than the non-dieters. Since these are people who effectively maintained their weight loss for an average of 11.5 years, perhaps artificial sweeteners aren’t so bad after all.

While the debate over artificial sweeteners has yet to be resolved, what is clear is that current levels of food consumption by many Americans are dangerously high, especially when the foods they are consuming offer little nutritional value. Saunders points to a recent survey of 7,318 fast-food lunch customers. They ordered meals averaging an astonishing 827 calories, or 41 percent of a day’s calories for an average person. Assuming people eat an equivalent amount for each meal, they’d be consuming nearly 20 percent more than they need to maintain a healthy weight. That 20 percent can easily by accounted for by three large, sugar-sweetened soft drinks.

As BikeMonkey notes, coming up with a well-controlled study to decide once and for all whether artificial sweeteners can help reduce obesity is a difficult proposition. But it’s critical to find an answer to the obesity epidemic in America and the rest of the world. As scientists look for solutions to the problem, you’ll find discussion of their findings on ResearchBlogging.org.

Originally published November 4, 2009

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