BIG Nutrition: Hydration—Time to bring out the birthday suit!


BIG Nutrition: Hydration—Time to bring out the birthday suit!

Summer brings hot weather, days at the beach, and inevitably a lot of sweating during WODs, so ensuring adequate fluid intake can be tough!

So, how much fluid is needed?

  • Throughout a day: Most people use the formula of half of one’s body weight in ounces of water/day or approximately 10 cups (80 ounces) for a person weighing 160 lbs for example. However, this is only a general guide. Heat and sweat loss can lead to more fluid needs. Also, more recently released recommendations from the National Academies of Sciences, Engineering, and Medicine recommend ~15.5 cups (3.7 liters) for men and ~11.5 cups (2.7 liters) for women of fluid per day.
  • Before a WOD: Consume 10-20 ounces (320-640 mL) in the 2-4 hours before the workout; this is sufficient for most people.
  • After a WOD: Consume water, as needed, so that urine is pale yellow.

Is there a way to determine the amount of fluid lost (sweat) during a workout?

  • Weigh before and after exercise naked for more accurate estimate of fluid loss.
  • Consume 42-50 ounces (1.25-1.5 L) for every 2 lbs (1 kg) of body weight lost.
  • Repeated measures help approximate average sweat loss.

Does food contribute to fluid intake?

  • Yes! Food provides about 20% of fluid intake each day, so occasions of low fruit and vegetable intake (eg, pizza night) require more fluid intake and it is important to get back to eating fruits and vegetables to ensure adequate hydration! In certain circumstances, exercise > 60 minutes or multiple WODs, fluid with a small amount of salt (1/4 tsp. in 32 oz (4 cups) water rehydrate better than plain water. 

Staying hydrated is more than nice, it is necessary for proper muscle function. Even mild dehydration is associated with reduced athletic performance, so test out your sweat loss the next time that you are at CrossFit Boston Iron and Grit

Happy and healthful eating,

Donna G. Pertel, MEd, RD, LDN

Have questions about nutrition for an athletic event? Contact me at [email protected]. Private Nutrition Services are available for BIG Members (@ 30% discount) and the Community. More information is listed here.