The Water Diet

Can you lose weight just by drinking more water?

Bloomimage / Corbis

Water is a tame beverage with a tumultuous public-health history. For decades, doctors said we should be drinking eight glasses of the stuff each day. By the time Michelle Obama had built a campaign around water, the backlash had begun.

“There’s no real scientific proof that, for otherwise healthy people, drinking extra water has any health benefits,” Indiana University pediatrics professor Aaron E. Carroll wrote in The New York Times last year.

A new study suggests there is a benefit, though—a big one. Drinking water might just help you eat less. According to the paper, published in the Journal of Human Nutrition and Dietetics, drinking more water is associated with eating fewer calories, as well as less sugar, salt, and cholesterol.

For the study, researchers from the University of Illinois at Urbana-Champaign looked at a dataset of 18,311 adults who were interviewed about everything they ate and drank on two different occasions, between three and 10 days apart. The amount of water each individual drank didn’t vary much between the two days. However, by running their answers through a simulation based on the entire dataset, the researchers found that an increase in daily plain water consumption by between one and three cups correlated with a reduction in daily total energy intake by between 69 and 206 calories. That might sound small, but 206 daily calories amounts to a pound of fat in about 17 days. There was also a reduction in sugar intake by between 6 and 18 grams, sodium by between 78 and 235 milligrams, and cholesterol by between 7 and 21 grams.

Ruopeng An, an assistant professor in kinesiology at the University of Illinois and lead author of the study, said there were two reasons why water might make people more abstemious. First, there’s the substitution effect: People might be drinking water instead of sugary beverages. Second, they might feel more satisfied with a belly full of water, so they won’t eat as many snacks.

He said he’s not sure if this strategy would work similarly for seltzer or sparkling water, or for artificially sweetened drinks. “The percentage of people who drink sparkling water is pretty low,” he said, which suggests he and I run in very different circles.

If An’s findings are replicated, they could be noteworthy. Research so far has been mixed on whether drinking more water helps with weight loss—or does anything in particular. It’s certainly easier to lose weight by sipping Dasani than by avoiding french fries.

Jennifer Kuk, a professor of kinesiology at Canada’s York University, who was not affiliated with the study, said there is some truth to the idea that water can reduce calorie consumption by filling up the stomach. But “in general, the effect is pretty minor as your stomach will get stretched over time," she said.

There have been a few other studies that have shown water could be used as a weight-control tool, especially if it’s chugged right before a meal, according to Yoni Freedhoff, a Canadian obesity expert who was also not associated with the study. But he cautioned that the effect was minimal—just a couple of pounds a year.

Finally, it’s important to note that dietary recall, the method used in this study, is notoriously flawed. Most people can’t remember what they ate down to the gram. Charles Burant, the director of the Michigan Nutrition Obesity Research Center, threw the most cold water on water, saying, “the investigators didn’t report on what one would have predicted … [that] those who drink more water weigh less. If water decreases caloric intake, then those who have the highest intake, shouldn’t they weigh less?”

“This study should not be used as evidence that if you drink more water, then you’ll eat less,” he concluded. “That’s been around a long time and that just doesn’t seem to work.”

An and several others said the study is but further evidence that people should try to avoid sugar-sweetened beverages in favor of water.

Burant also suggested a counterintuitive way that water consumption might be keeping people away from the cookie jar: “Perhaps the heavy water drinkers are in the bathroom more often, reducing the time they [have] to eat?”