Does Diet Soda Make You Fat?

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Do you think diet soda makes you fat? We talked about this last year and many of you posted your thoughts on my blog at ThirdAge.com. The topic came up when a college friend of mine was visiting. I picked her up at the airport and she wanted to stop for a case of diet soda. She easily drinks five cans a day. As we were loading the car, she said, “Do you think drinking diet soda makes you fat?”

“Can Sugar Substitutes Make You Fat?” an article that recently appeared on Time.com, stated that new research on weight loss points out that your body is not easily tricked and that sugar substitutes are not key to weight loss.

Researchers from Purdue University compared eating habits and weight gain in rats whose diets contained foods sweetened with either zero-calorie saccharin or glucose…aka sugar. The study which appears in Behavioral Neuroscience finds some interesting results.

Rats who received artificially sweetened yogurt over a two week period consumed more calories and gained more weight than rats who received yogurt flavored with glucose. This research continues the work that the Purdue scientists began in 2004 when they reported that animals fed saccharin-sweetened liquids and snacks ate more than animals fed high-calorie, sweetened foods.

This research suggests that artificial sweeteners somehow disrupt the rat body's ability to regulate incoming calories. Remember Pavlov’s dog who was trained to salivate at the sound of a bell? It seems that animals are trained to anticipate calories when they taste something sweet. Think about it. Typically a sweet food has a significant number of calories. When the animal eats a saccharin-flavored food with no calories, the sweetness and calorie link is broken and the animal tends to eat more and gain more weight. Why? It seems that the bodies of the rats learn to expect fewer calories from artificially sweet foods so the animal responds and consumes more calories.

The study goes on to suggest that animals given artificial sweeteners respond differently to their food than those eating high-calorie sweetened foods. This is fascinating. It seems that the rats receiving the glucose had an increase in core body temperature at mealtime which corresponded to the expectation of calories that would need to be burned off. The saccharin-fed rats did not have an increase in body temperature. According to the researchers, the rats receiving the artificial sweetener don't anticipate as many calories coming in which results in a more sluggish metabolism that stores, rather than burns, excess calories and that they tend to eat more.

This research was conducted rats and we cannot extrapolate that to cover humans. However, previous research from the University of Texas Health Science Center in San Antonio reported that adults who drink diet soda (we’re talking only one can or bottle a day) did not lose weight. They were actually more likely to become overweight than those adults who did not drink soda at all OR those that drink regular soda. In fact, the more diet soda consumed, the more likely someone would become overweight. To be specific, there was a 41% increase in the risk of being overweight for every can or bottle of diet soda consumed daily.

It seems that artificial sweeteners may affect the body’s ability to judge how many calories you consume because you are getting something sweet without any calories. When no calories are consumed, the body may continue to crave what it expected and could lead to overeating or bingeing. Similar outcome to the rats.

So do you dump the diet drinks? What about sugar? Can’t too much lead to weight gain and a host of spin-off issues such as diabetes and heart disease? Absolutely. Aren’t artificially sweetened products a life saver for diabetics? You bet. I don’t think we have the answer yet. Yes, we know that calories in versus calories out determine weight loss and weight gain. But is there another facet to this? Is there a behavioral component relating to what the body expects to receive? The best bet until we know more is to be aware if and how artificial sweeteners affect you. Do you feel satisfied when you consume them? Do you want more food? Crave more food? If so, cut back your use and see what happens. If they don’t seem to be an issue for you in terms of how much food you eat, at least you’re aware.

Your take home message is until we know more about sugar substitutes as they’re related to weight, remember that we do know that portion size remains key to successful weight management.