Blog | Friday, November 4, 2011

QD: News Every Day--The cold, hard truth about water and weight loss


Does drinking cold water really help you lose weight? It's an urban myth, except that like most lies, it has some truth to it.

WATER By grggrssmr via Flickr and a Creative Commons licenseWhile it's probable that drinking water before a meal induces satiation sooner, and eating less, researchers have looked at another aspect of this myth, that the body burns calories raising the temperature of cold water.

A few articles from the journal Obesity have tracked various attempts over the years to learn more about the subject. In the first study in 2006, researchers concluded that pre-meal water consumption reduces meal energy intake in healthy, non-obese adults ages 60-80, but not in those ages 21 to 35.

Thirty minutes before the lunch, women were given 375 mL water and men 500 mL, or were assigned to a control group that didn't drink water. There was no significant difference in meal energy intake between conditions in the young subjects (892 + 51 kcal for those without water vs. 913 +/- 54 kcal for the water drinkers, P=0.65).

However, meal energy intake in those who drank water was significantly reduced compared to the nondrinkers among older subjects (682 + 53 vs. 624 +/- 56 kcal, P=0.02). This effect was caused primarily by the reduction in meal energy intake after water consumption in older men.

In the second study, published in August 2009 at Obesity, researchers looked at whether drinking water before meals for 12 weeks helps weight loss among overweight and obese middle-aged and older adults also following a low-calorie diet.

In this study, 48 adults ages 55 to 75 years were assigned to a low-calorie diet with or without drinking 500 ml water. At baseline and week 12, each participant underwent two test meals with or without drinking water beforehand. Meal energy intake was assessed at each test meal and body weight was assessed weekly for 12 weeks.

Weight loss was about 2 kg greater in the water group than in the nonwater group, and the water group (beta=-0.87, P less than 0.001) showed a 44% greater decline in weight over the 12 weeks than the nonwater group (beta=-0.60, P less than 0.001). Test meal energy intake was lower in the water drinkers than nondrinkers at baseline, but not at week 12.

Researchers concluded that drinking 500 mL of water before a meal leads to greater weight loss than a low-calorie diet alone, in part to an acute reduction in meal energy intake.

To examine the idea specifically that cold water might have an effect on weight loss, researchers published a third study in International Journal of Obesity in July 2011. Here, researcher claimed a positive effect on weight loss.

Researchers looked at 21 overweight but otherwise healthy children who drank 10 mL/ kg−1 of water at 4 degrees Celsius. Resting energy expenditure was measured before and after drinking, for 66 minutes.

Immediately after drinking water, there was a transient decrease in resting energy expenditure, from a baseline value of 3.32 +/- 1.15  kJ per min to 2.56 +/- 0.66  kJ per min at minute 3 (P=0.005).

Resting energy expenditure rose significantly higher than baseline after 24 min (3.89 +/- 0.78  kJ/min, P=0.021), and at most time points thereafter. The greatest effect was seen 57 minutes after drinking (4.16 +/- 1.43 kJ per minute, P=0.004), or 25% higher than baseline.

The researchers concluded that consuming the recommended daily amount of water for children could result in an energy expenditure equivalent to an additional weight loss of about 1.2 kg per year.

But how much energy is really consumed by the body warming up cold water? Physicians and researchers from Cambridge University chimed in on the subject using some back-of-the-napkin math to calculate how much energy is expended drinking a liter of cold water and expelling warm urine. It's about the same amount of energy gained from eating an apple. Their solution is to start chugging quick.