Body of Water

As I am sure you know, water makes up a large percentage of your body weight, about 60 percent.  Every system in your body depends on water and a lack of water can lead to dehydration, which causes the body to not function properly.  Even mild dehydration, as little as 1-2 percent loss of body weight (from fluids) can make you feel like you don’t have energy and are tired!  If you are struggling to get through your day, check your fluid intake.  You may be slightly dehydrated.



Signs and Symptoms of Dehydration Include: excessive thirst, fatigue, headache, dry mouth, little or no urination, muscle weakness, dizziness, or lightheadedness.

How Much Water Does a Person Need?  Is this amount the same for a weight loss surgery patient?  You lose weight everyday through sweating (not all sweating is noticed), exhaling, urinating, and bowel movements.  You should continue to replace this water daily by consuming foods and beverages that contain water.  Healthy adult fluid intake can vary tremendously.  There are several ways to determine water recommendations (for healthy, sedentary adults living in a temperate climate):

  1. Replacement therapy – Average urine output for an adult is 1.5 liters per day.  You also lose almost another liter of water a day through breathing, sweating, and bowel movements.  Food accounts, on average, for 20% of intake, so if you consume 2 liters of water (a little more than 8 cups), along with normal foods, you can replace lost fluids.
  2. Eight 8-ounce glasses of water per day – Many people have heard this recommendation.  Some have termed it the “8 x 8 rule.” If someone were to consume eight 8-ounce glasses of water a day it is equivalent to 1.9 liters.  However, this approach is not supported by scientific evidence.  However, it is easy to remember and a good basic guideline.
  3. Dietary recommendations – The Institute of Medicine (IOM) recommends that men consume 3 liters (~ 13 cups) of total beverages per day and that women need 2.2 liters (~ 9 cups) of total beverages per day.  These guidelines were developed from national food surveys that assessed individual’s average fluid intake.

You Can Choose any of the above methods to achieve a balanced hydration (water) status.  A rule of thumb I always shared with my patients was: you are probably well hydrated if your urine is pale in color (colorless or slightly yellow) and odorless.  Not a fun thing to discuss – but now you will remember!

Weight Loss Surgery patients (long-term or after 6-9 months post-op) can consume the recommended amount of water and it is just as important for them to consume the recommended fluid as any other person.  This recommendation may be difficult to maintain early out of surgery (day 1 post-op to 9 months post-op), so just focus on doing your best and trying to get in one more sip than you did the day before 

Some Factors that May Modify Your Needs.  If you are extremely active, live in a hot and/or humid climate, pregnant, and/or breastfeeding you may need more water than the standard recommendations.  Your health status may also play a role.

  1. Exercise.  If you exercise or engage in activity that makes you sweat you will need to consume extra fluid to compensate for the extra fluid lost during physical activity.  During activity, replenish fluids at regular intervals and continuing drinking water or other fluids after you are finished.
  2. Environment.  You should consume extra water in a hot or humid environment to help lower your body temperature and to replace the fluid lost through sweating.  You may also need extra water in cold weather if you sweat while wearing insulated clothing.  Heated, indoor air can cause your skin to lose moisture, increasing your daily fluid requirements.
  3. Illnesses or health conditions.  Some signs and symptoms of illnesses, such as fever, vomiting and diarrhea, cause your body to lose extra fluids.  To replace lost fluids, drink more water or fluids with electrolytes included (like Gatorade, Gatorade G2, Pedialyte, etc.); however, watch the sugar intake if you are a gastric bypass patient.
  4. Pregnant or breastfeeding.  Women who are pregnant or breastfeeding need extra water to stay hydrated and to replenish lost fluids, especially when nursing.  The IOM recommends that pregnant women should drink nearly 10 cups of water/fluids per day and a women who breastfeed should consume nearly 13 cups of fluids per day.

By Heather Mackie, MS, RD, LD 

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