Can drinking water before a meal help you lose weight?

“Drinking a lot of water has long been a staple of weight-loss programs, in part because doing so makes you feel fuller,” wrote the Washington Post in 2020.

What studies of drinking water and food intake have found

“We have done a couple of studies where we gave folks two cups of water before a meal, presented them with a large tray of food, and asked them to eat as much as they’d like,” explains Brenda Davy, professor of human nutrition, foods, and exercise at Virginia Tech.

“After drinking water, middle-aged and older adults ate about 60 to 75 calories less than when they didn’t drink water before their meal.” (Water had no impact on how much younger adults ate at their next meal.)

“So the question was, if you drank water before a meal repeatedly over a period of time, could it promote weight loss?” Davy wondered.

To find out, “we prescribed a structured weight-loss diet of 1,200 to 1,500 calories per day to 48 middle-aged and older adults with overweight or obesity.”

“One group was not given any instructions about water intake, while the other group was told to drink two cups of water prior to each main meal. And we provided the water group with bottled water.”

After 12 weeks, “the water group had lost about 15 pounds and the control group had lost around 10 pounds,” says Davy. (That study, as well as one of the single-meal studies, was funded by a nonprofit organization that received money from the water-filter maker Brita.)

How does water help people shed pounds?

“We have some evidence that people feel more full before eating a meal if they drink water first,” says Davy. “Another possibility is that folks may drink water instead of calorie-containing beverages.”

But Davy is cautious. “We have preliminary evidence supporting the effectiveness of pre-meal water to help people lose weight, but those findings need to be confirmed with a larger study,” she says.

What’s more, “we’ve only seen a benefit in middle-aged and older adults. Whether this works in younger folks is a big question mark.”

The bottom line

Drinking water before a meal may help you eat less. Just don’t expect the pounds to melt away.