When overweight or obese people drink a glass of water on an empty stomach while sitting still, their body burns a few extra calories, possibly because the water makes their cells swell and wake up their metabolism.

Drinking a large glass of water on an empty stomach can make your body burn a few extra calories, especially if you're overweight, because it tricks your cells into thinking they're hydrated and need to work harder.

For people who are overweight, drinking a glass of water on an empty stomach can slightly boost calorie burning, but this doesn’t happen in people with normal weight.

When overweight people on a diet drink more than a liter of water a day, they tend to lose more weight—even if they don’t eat less—possibly because water helps their body use insulin better and reduces cellular stress.

If you're trying to lose weight and you drink over a liter of water every day, you might lose more weight—even if you're eating the same amount—because it helps your body manage insulin and stay hydrated.

If overweight people drink more than a liter of water a day while eating less, they lose more weight — even if they’re not eating fewer calories overall — possibly because their insulin levels drop and their body burns fat better.