From the Moderators - A word on Fluid Needs

In response to the many questions we have received on fluid needs we offer the following.  Please feel free to comment, offer your evaluation, and any other thing you would like to add.

A word on fluid needs:

 

                How much water should you drink every day?  It is a simple question, but it doesn’t have an easy answer.  We know tha****er is the principle chemical component of our body, comprising approximately 60% of our total weight.  Every system in your body is dependent upon water – to flush out waste, deliver nutrients to your cells, and provide a moist environment for membranes.  The importance of water is unquestionable, but still, how much do we need?

Recommendations for fluid intake can vary widely.  Many of us have heard the old advice for 8 oz, 8 times per day.  If you calculate that out, it is the same as the 64-oz that most dietitians recommend post WLS.  But is this the correct amount of fluid for you? 

Studies on fluid needs have produced varying recommendations for fluid intake over the years.  In 2004, researcher Heinz Valtin decided to question the 64-oz per day recommendation.  What he found was that there was inadequate evidence that healthy adults living in temperate climates and not engaged in rigorous activities need large amounts of fluids.  He further recommended that people should drink when they are thirsty and that even caffeinated drinks count toward your fluid total.  In 2004, as a response to this evidence, the Institute of Medicine (IOM) issued new recommendations for fluids, which were translated loosely into new RDIs.  The new RDIs allow for water to be counted as “total water” which means the water in your food, beverages, and water count toward your goal.  Food is expected to provide 20% of our fluid and the other 80% from beverages including water.  Keep in mind that these new recommendations are accompanied by the fluid goal of 91 oz for women and 125 oz for men (almost 2.7 liter for women and 3.7 liter for men) which is more than the old recommendations.

The bottom line appears to be tha****er needs depend on many factors including your health, activity level and where you live.  Also take into consideration that the studies on fluid needs were not done on post-WLS people, but on healthy adult volunteers.

 

There are a few ways to calculate the amount of fluid that you need (and some additional information specific to WLS):

·         Method #1 Dietary recommendations – these are the RDIs as stated above 91 oz for females, 125 oz for males.  There are listings of the water contents of foods – a few examples in % water: Lettuce 95%, watermelon 92%, grapefruit 91%, carrot 87%, yogurt 85%, apple 84%.

·         Method #2 Replacement method – average urine output for adults is 1.5 liter (50 oz) per day, you can lose an additional 500-1000 ml (17-33 oz) through breathing, sweating, and bowel movements.  If you are brave, you can measure your own output, add 1 liter (33 oz) for losses and make that your goal.

·         Method #3 Calorie based – For every calorie consumed, drink 1 ml of water.  This is probably not useful for people on very low calorie diets or restricted by WLS, as the average calorie intake can be less than 1000 per day. (1 liter = approx 33 oz)

·         Method #4 Weight based – There are a few formulas for this method.  The most common is for every kilogram of body weight, allow for 35-ml water.  The more complicated formulas start with a base fluid level then add more sequentially to account for body weight (these get very complicated – good for the math whizzes out there) - for English measure, take weight in lbs, divide by 2.2 to get your weight in kg.

·         Method #5 Thirst based – this one is pretty simple, drink when you are thirsty, plan on 7-12 trips to the bathroom to urinate each day, and drink more when it is hot outside, your activity increases, or if your urine appears concentrated.  It might be hard to tell how concentrated your urine is if you are taking a lot of supplements.

  

The most common method for dietitians to use is the ml/kg method – here is where calculations of body weight can come in to play.  That information is in a separate post.

The bottom line for most people is tha****er is a necessary nutrient.  Withou****er, you will die.  If your kidneys are healthy, the more water the better!  If you have difficulty drinking water, research shows you can count the other things that you eat and drink into your daily fluid requirements.  Is there a set amount for everyone – the answer is no. Coming soon - adjusted vs actual body weight

would you transfer this into ounces/cups/gallons for us that are not metric literate! My kids can do the metrics but we only touched on it lightly when I was in school. I drink about 1 gallon of water a day and if I don't, I really notice it. I have also found that being hypothyroid makes my skin and eyes dry so I make sure I drink plenty! Diona

I went back in and did some addition of english measure - I hope that helps.  I did not convert the ml water x kg body weight.  For conversion sake: 8 oz = 240 ml 500 ml = 17 oz 1000 ml (or 1 liter) = 33 oz 1500 ml (or 1.5 liter) = 50 oz 64 oz = 1920 ml  I hope that makes it a little easier!

Hi, Diona!  Here is the info that I used to figure out the water intake formula that Melania provided in an earlier thread.  Hope that it helps.  Ro The RD is using Kg; rather than lbs so that has to be converted first before the formula can be used. The number 2.206 is the correct number to use to change Kg into the same amount of lbs that you weigh. You have to divide your weigh by the number 2.206, which gives your weight in Kg. You have to multiple your Kg weight x 40 cc, which gives the amount of water needed for your weight in the cc amount. The cc amount has to be converted back into ounces. To change cc into ounces, you have to divide that rather high "cc fluid per day" number by 240 cc. The amount on the calculator is in "cups" per day; not ounces. When you multipe the "cups" per day amount by 8, you get the number of ounces to drink per day... if you were a generally healthy person...without WLS.