A friend is only drinking water because she wants to lose weight, surely that can't be good?

Water intake: Water is good stuff, and the truth is that most people do not drink enough water (about 2 liters a day is recommended). Lot's of time we munch on snacks because we think we are hungry, when actually we are just thirsty. So a lot of water consumption is generally a good thing. In the past many diets have proposed drinking a lot of water (eg., 8 glasses a day) as part of an effective diet.