Not exactly a surprising result, but likely one that will be poo-poo'd by all those who love to vilify artificial sweeteners.
Researchers in New Zealand studied folks who had successfully lost weight and their dietary consumption patterns. More specifically they looked at folks who had maintained a weight loss of greater than 10% of their weight for 11.5 years and they compared these folks' dietary strategies to folks of similar weights who had never been overweight.
What unshocking yet valuable results did they find?
They found that folks who lost the weight had to work harder at their dietary strategies to help keep that weight off than folks who never had weight to lose. Their strategies included consuming fewer calories from fat (though the importance of this one's debatable as the 90s were the low-fat decade and more recent data from the National Weight Control Registry suggest that low-calorie is of course more important than low-fat and can be accomplished many different ways), consuming more of sugar and fat modified foods (reduced fat, reduced sugar), consuming more water, less pop and three times more daily servings of artificially sweetened soft drinks.
Go figure - folks who are predisposed to weight gain can help themselves keep the weight off by employing dietary strategies to help themselves consume fewer calories.
Go ahead, drink your diet Coke.
Phelan, S., Lang, W., Jordan, D., & Wing, R. (2009). Use of artificial sweeteners and fat-modified foods in weight loss maintainers and always-normal weight individuals International Journal of Obesity DOI: 10.1038/ijo.2009.147