A: There's no compelling evidence to show drinking water helps with weight loss.
When it comes to losing weight, most of us are willing to try anything; well at least anything that doesn't involve eating less and moving more.
One popular theory says that if you drink more water, you will lose weight. The belief is that drinking water helps suppress your appetite.
But is the answer to weight loss really as simple as guzzling an extra glass or two of H2
Not likely, says Professor Neil King, coordinator at the Human Appetite Research Centre at Queensland University of Technology in Brisbane.
"There's no compelling evidence to support the idea that drinking water suppresses appetite significantly, and therefore leads to weight loss," King says.
"Some people might anecdotally report that they drink lots of water and they lose weight, but that doesn't mean that drinking water is causing the weight loss."
A research review published in 2013 did suggest drinking water before a meal could help those who were overweight and on weight loss diets to lose weight, along with other weight loss measures. But the authors concluded evidence linking increased water consumption with weight loss was limited
, and this was mainly due to a lack of good-quality studies.
One reason King doesn't believe this theory stacks up is because liquids tend to pass through your gut very quickly.
Food, in contrast,"takes longer to digest, longer to come through the gastric system" and therefore you feel satisfied for longer than if you have merely consumed liquids, King says.
This is why people trying to lose weight are often encouraged to avoid consuming too many kilojoules in the form of drinks, as it's too easy to guzzle more energy than you need in liquid form and still feel hungry.
(You probably couldn't eat four oranges in one go, and even if you could, you probably wouldn't want to eat anything else for some time afterwards. Yet most of us can easily drink a big glass of orange juice (with the same amount of kilojoules as four oranges) and still tuck into a big bacon and egg fry-up.)
Associate Professor in Nutrition at Deakin University Tim Crowe says this is one of the issues with soft drinks.
"One of the reasons why soft drinks are more linked to obesity than other forms of pure sugar is because you can drink quite a lot of calories quite quickly before you start feeling full."
Obviously water doesn't contain any kilojoules, so drinking more of it won't make you gain weight, but King says it's unlikely to put the brakes on your appetite either.
"If you drink two and a half to three litres of water in one go, there's going to be a fairly short-term satiety effect maybe – because you have gastric distension [swelling of your stomach]– but it's so rapidly emptied that it's short-lived."
So even if you did manage to drink enough water to make yourself feel full, King argues that feeling would pass (as the water passes through you) and you would soon be hungry again.
As for whether you are likely to confuse hunger and thirst, King says they are two very different sensations.
If you are thirsty, you'll be able to quench your thirst with water. But if you're hungry, drinking water is not going to satisfy you: "If you're going to satisfy the hunger then it needs some kilojoules in there as well".
Crowe says there are plenty of things he recommends that people do if they want to lose weight, but drinking more water is not one of them.
He says one possible way drinking water could help with weight loss is if you make a point of having a couple of sips at the start a meal to help you to focus on the act of eating, so you are able to enjoy every mouthful rather than shovelling food down your throat. But you don't need water to help you do this, you could also try taking a few deep breaths or just sitting for a moment.
"Where it can help, is not so much the water, it's introducing this idea of mindfulness, of actually being conscious of what you are eating and drinking. So if you have water with your meal, or you are drinking water before it or with it or after it, it can help make you more conscious of what you are doing and what you are putting in your mouth and that can be a good thing."