Ask the RD: Will Drinking More Water Help Me Lose Weight?

Q: Will drinking 2 litres of water per day help me lose weight?

We hear all of the time “you need to drink lots of water in order to lose weight”… but why? And what's "lots"? Why should you be carrying your water bottle (glass or stainless steel please) around with you during the day? Today we are going to dive into the topic of water and weight loss and hopefully clear up any confusion.

Like every other health and nutrition topic, there are mixed views on this issue. Some say that the moisture content of our food is high enough and we don't need to focus on water consumption but simply drink when we are thirsty. Others say that if we don't drink enough there is no way our fat cells can break down (a process called lipolysis) and as a result we cannot lose any weight. 

Let’s look at the research:

• Over a 12-week period, half of the study subjects drank 500 ml of water before a meal. By the end of the 12 weeks, subjects drinking 500 ml of water before meals had a 44% greater weight loss than the control group. This 44% decrease in weight equaled approximately 2 kg (4.4 pounds) (1). Over a 12-week period this is the equivalent of just under ½ pound per week, which is great!
• This study demonstrated that drinking 500 ml of water increased metabolic rate by 30% between 10-40 minutes after consumption. If we were to drink 2 liters of water per day, this increased metabolic rate would equate to approximately 400 kJ (which is just shy of 100 calories) per day. It must be noted that 40% of this thermogenic effect was due to the fact that the water had to be heated from 22 degrees C to 37 degrees C (body temperature) (2).
• This study was conducted on 173 pre-menopausal women (aged 25-50) who reported drinking less than 1 liter of water per day prior to the study. The diet, body weight, body fat percentage, waist circumference and activity level were monitored at various points throughout the study. Results showed that when water consumption was equal to or greater than 1 liter per day, an approximate weight loss of 2 kg over 12 months occurred (3). 

It is important to note: Consumption of unsweetened (non-caloric) beverages did NOT have a benefit similar to water. Take home: Drinking 2 liters of diet soda, diet iced tea, etc. does not produce the same benefit as drinking “plain” water.

• A final study was conducted over a period of 8-weeks on 50 overweight females. During the study, subjects were instructed to consume 500 ml of water 30 minutes prior to breakfast, lunch and supper. This additional 1.5 liters of water was over and above any other water they consumed throughout the day. Over the 8-week period subjects experienced a significant decrease in body weight, body composition and body mass index (4).

Although these studies seem promising as to why it is important that consume more than 1 liter of water per day, these studies do not demonstrate causation. As we’ve talked about in previous posts, it is difficult to control every aspect of a subject’s diet in a study for an extended time period. Methods of gathering data in these studies were typically a 24-hour recall on a scheduled basis (i.e. 2-months, 6-months, 12-months.)

Due to the nature of the study that would be needed to prove causation (that drinking more water actually CAUSED weight loss – regardless of how minute) this may be the most accurate research we can conduct at this time.

Although we cannot say with 100% certainty that drinking more water (approximately 2 liters per day) will have added benefit in terms of weight loss we do know that it could likely be beneficial and will not hinder weight loss.

Recommendations

I recommend that my clients consume 2 liters of water per day for two reasons:

First, we often mistake thirst for hunger (I’m sure you’ve all heard of this before). Have you ever experienced cravings for foods like grapes or a juicy apple? This is very likely a signal that your body is really craving hydration. You can often tell whether it’s a food or water craving based solely on the foods you’re craving. If you’re craving salty chips, it is unlikely that you’re really craving water since the moisture content of chips is extremely miniscule. Next time you have a craving, drink 500 ml of cold water and wait 20 minutes. This is often the key to feeling satisfied.

If we are focused on consuming 2 liters of water per day, we are likely replacing sugar-sweetened or non-caloric beverages (this includes Mio, Crystal Light and any of those drink mixes) in our diet with water. Replacing sugar-sweetened beverages with water will absolutely result in a decrease in body weight over time but what about non-caloric beverages? Many non-caloric beverages (i.e. diet drinks) are sweetened with artificial sweeteners, which can have a major impact on our population of good gut bacteria. If you remember from this post, having a robust population of good bacteria in our gut is extremely important if we are trying to maintain a healthy weight.

Tip: I don't typically recommend that any of my clients with digestive disorders drink water with their meals. Drinking water with meals can hinder the digestive process in many people due to its impact on digestive enzymes. Keep your liquid consumption to 30 minutes prior to or 30 minutes following a meal for optimal digestion.

Added Bonuses

In case you needed another reason to stay hydrated - Hydration status is linked tightly to mood. If you remember from this post, studies show that even slight dehydration can increase feelings of depression in some people.

We must also remember that the major ways our body detoxes is through urination, defecation and sweating - all which rely on adequate hydration levels to occur. If we are not drinking enough water (and the "enough" can be different for many people depending on climate, activity level, etc.) these detox pathways are hindered, which can lead to suboptimal health status. You will want your urine to be a light yellow color - not clear or dark yellow. It may sound crazy but monitoring the color of your urine can be a simple and effective way of monitoring your hydration status!

How much water do you drink each day? Share in the comments below. And don't forget - if you have any questions that you'd like to be answered, please don't hesitate to submit them here!

Yours in Health,

Kristin