nos-trum. pronunciation: \nos'-trum\. noun. Etymology: Latin, neuter of noster our, ours.
1. a medicine of secret composition recommended by its preparer but usually without scientific proof of its effectiveness.
2. a usually questionable remedy or scheme.
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Thursday, November 18, 2010

The Water-Drinking Controversy In Weight Loss

A number of people have claimed that pre-meal water loading can be an adjunct to calorie-restriction in weight loss plans.

Now there's a study (ina the journal Obesity, Feb 2010, see link for abstract) that shows an impact.  It aint a great study, though.  With only 48 participants, including the controls, it doesn't have a lot of power.  Adopting a critical attitude, you start asking whether this small group has some selection bias, or other characteristics that make them not typical for the whole population.  Two that jump to mind right away are (1) these 48 people were not in the very obese category (max BMI of 40), and (2) they were middle-aged and older.

And the period over which the study occurred is only 12 weeks.  For a popular review of the research, see here.

However, for what it's worth, the experimental group drank two glasses of water prior to meals, and experienced a 44% increase in weight loss by the end of the 12 week period.  44% sounds like a lot, but in terms of pounds lost was 15.5 versus 11.  This occurred while both groups were on a hypocaloric diet...that is, reduced calories per day, but I'm not sure how much.

Nothing cosmic about water is going on here.  We reach "fullness" while eating when the expanded stomach sends a message to the brain that says, "You should stop now."  It's a mechanical effect to pre-load the stomach in advance with water, leaving less room for food.

Parenthetically, I've had patients that assuage hunger in-between meals by sipping water.  It works for some.  So, in general, this is a decent enough strategy to get a head start on limiting caloric intake.  It avoids having to take medicine, or other more bizarre products, to accomplish the goal of weight loss. 

A reasonable approach is to reduce calories below your baseline needs by about 500 a day, and drink two 8 oz glasses of water prior to eating.  Unless you have a medical condition that limits your ability to withstand calorie reduction; if you're under treatment, talk to your doctor.

An unexplained  (but fascinating) finding is that the calories consumed at the beginning of the experiemental period was lower in the water group, but by week 12, the water group was taking in just as many calories as the no-water group.  This may just be the phenomenon we run across all the time:  people find a way around restricting the content and quantity of intake (like laws to change Happy Meal contents...folks will just eat somewhere else).

For Onion Peelers,
Weight loss was ~2 kg greater in the water group than in the nonwater group, and the water group (beta = -0.87, P < 0.001) showed a 44% greater decline in weight over the 12 weeks than the nonwater group (beta = -0.60, P < 0.001). Test meal energy intake  was lower in the water-preload group than the no-preload group at baseline, but not at week 12 (baseline: WP 498 +/- 25 kcal, NP 541 +/- 27 kcal, P = 0.009; 12-week: WP 480 +/- 25 kcal, NP 506 +/- 25 kcal, P = 0.069).

One big caveat.  There are people who overdo anything.  Compulsive water drinkers, or water drinking contest participants (if you can imagine such nonsense), can develop a syndrome called water intoxication.  Nothing to worry about really; 16 oz prior to a meal is nothing.  We're talking gallons over a few hours, in order to cause problems.  But the point is, no one should assume that since two glasses helps, more will be better.

People who are prone to that type of thinking are eligible for the Darwin Award.

Doc D
The above is not intended to be treatment advice.  It's just a discussion of research results, and what they could mean.

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