Chug a couple glasses of water before eating a meal, and you may eat less without even trying.
Those are the results from a new study published in the journal Obesity, in which researchers rounded up obese adults to see if drinking water before eating could help them shed pounds.
“If you look at any sort of weight management programs, they all say drinking lots of water is a really good thing,” says study author Dr. Amanda Daley of the University of Birmingham in the UK. “We said, let’s go see what the actual evidence is for this.”
Finding little in the literature, Daley and her colleagues recruited 84 adults with obesity for a 12-week experiment. Everyone was given general weight loss advice, then assigned to one of two groups. One group was told to drink 500 ml—about 16 oz—of water half an hour before their meals, while the other group was told to simply imagine their stomachs were full before meals.
The researchers monitored everyone's weight at the start, middle and end of the experiment, along with their urine to make sure the water-boosted group was indeed drinking more water. They kept track of physical activity, too, which didn’t change.
The group that loaded up on water lost about three more pounds than the group that didn’t up their water intake. And the more they drank, the better the results; people who drank 16 ounces before every meal lost about 4.3 kg, or 9 pounds, over the course of the experiment. “That’s about what you get from going to Weight Watchers for 12 weeks,” Daley says. “That’s a real success.” (Weight Watchers counts weekly weight loss of half a pound to two pounds as on track.)
Water might be so effective because, obviously, "it fills you up" and helps increase satiety, Daley says. Drinking a couple glasses of water 30 minutes before a meal gives you time to feel fuller, which can help shape decisions about what you eat, she adds.
This is just a first step at getting good evidence, and more research is needed before the mechanisms are fully discovered. But Daley thinks that drinking more water before meals can help everybody with weight management, regardless of BMI status. “We all get fatter over time, so it might well work as a prevention strategy at a population level,” she says. “We want people to drink more water anyway.”