If you drink a pint of water before each of the three meals of the day, you could lose up to an extra 38 lbs (17 kg) over a year-but that assumes you rigidly follow the regime and you're already obese with a lot of weight to lose.
It's been tested on a group of 84 obese people, 41 of whom were told to drink the water before every main meal and the rest were asked to imagine that they had a full stomach before eating.
Not everyone in the water group followed the guidance properly, but those who did lost an impressive 9.48 lbs (4.3 kg) over the three months, although the average loss was 2.8 lbs (1.3 kg).
Those who didn't drink before meals, and just followed a sensible eating and exercise plan, lost 1.7 lbs (0.8 kg) over the three months.
(Source: Obesity, 2015; doi: 10.1002/oby.21167)