A common piece of advice for eating less food off your plate—drinking lots of water at the same time—might unfortunately be bunk, recent research suggests.
Scientists at Cornell University and Pennsylvania State University examined data from two earlier randomized trials. People who drank more water during their meals actually tended to consume more calories, they found. People who regularly switched between drinking and eating were also more likely to consume more, perhaps helping explain why water can ramp up people’s hunger, the researchers say.
“This finding challenges the widespread dietary advice to drink water with meals to reduce food intake,” they wrote in their paper, published last month in the journal Appetite.
A trick that doesn’t work
The notion that drinking water before or during a meal can help cut calories is definitely popular. A 2019 study found, for instance, that roughly a quarter of Americans trying to lose weight had used that particular strategy in recent years—making it the third-most common approach for weight loss, next to exercise and actively trying to reduce food consumption. The basic idea behind it is that water should literally fill up your stomach, making it easier and quicker for you to feel full.
However, according to the authors, relatively little research has actually tried to validate this hunch, and the few relevant studies looking at it have provided mixed or contradictory results. A 2023 study of people who ate lunch in a lab setting from one of the authors, Paige Cunningham, actually found the opposite pattern: people who drank more water ate more of their lunch on average.
Cunningham and co-author John Hayes decided to take another look at this hypothesis, reanalyzing data from two other lab experiments of theirs, which were originally meant to test how the spiciness of a meal might affect calorie intake. They were particularly interested in examining the role of switching between drinking and eating as an explanation for why water can counterintuitively increase consumption. Since we tend to eat less of a food as it becomes more familiar (a trait we probably share with cats, by the way), taking a water break could restore some of the meal’s novelty and encourage us to keep eating.
The two experiments collectively involved 86 adults who ate one of two lunches: chicken tikka masala or beef chili. The more water people drank alongside their meal, the more they ate on average, with every extra 100 grams of water linked to an extra 39 grams of food, or roughly 49 more calories. Switching, too, was associated with greater food consumption, with each switch between food and water linked to an extra 4.4 grams of food.
“[W]ater empties quickly from the stomach, so it likely doesn’t fill us up for long. Instead, water may increase how much we eat, providing lubrication that can speed up eating and preventing dry mouth, which can prolong enjoyment of the food,” said Cunningham, an assistant professor in the Division of Nutritional Sciences in the College of Human Ecology at Cornell, in a statement from the university.
And a trick that might work
The researchers note their findings are based on a secondary analysis that only looked at associations. That said, they are planning to follow up with further research that can more definitively show a cause-and-effect relationship between drinking more water and eating more food. And while water might not be the diet aid people claim it to be, the researchers did find evidence of another trick with more backing: spiciness.
In both this study and a related one, published this past April, the researchers found that adding more spices to people’s food, either a meal or snack, can slow down people’s eating and reduce calorie consumption, without necessarily sacrificing their enjoyment of it. More research will be needed to tease out exactly how spiciness can affect food consumption across different types of meals and in the real world, of course, but it’s at least a glimmer of hope for people still looking for a life hack to reduce their calories.
“We are looking to future experiments that explore what other factors or properties of foods we can leverage to influence behaviors,” Cunningham said.
