# Weighing before and after sport to determine lost water

Would weighing myself before and after sport give an accurate estimate of how much water I lost? As in, if I weigh 1kg less after sport, that would suggest that I lost one liter of water?

• If nothing was consumed during that period or you included consumed liquid into that calculation, then sure. Any weight variance across a 1-3 hour period will be almost entirely due to liquid and/or food consumption/loss. – JustSnilloc Feb 12 at 16:06
• And the lost weight due to CO2 that I might breathe off is negligible? – Olfway Feb 12 at 16:12
• A quick google search suggests that a person emits 2.3 lbs (~1kg) of CO2 per day. Divide that by the hour and you get 0.095 lbs (0.043kg) per hour. Naturally it will be slightly more while awake and especially while active, but even if it's double or triple that rate I would argue it to be negligible, yes. This is because you want to keep in mind that your body strives to keep a net balance of CO2, so despite losing some, you are also gaining some - a continual process of addition and subtraction. – JustSnilloc Feb 12 at 16:32
• Why do you ask? This is such a basic question, I'm wondering if there is more to it – Raditz_35 Feb 13 at 11:15
• It's going to be a combination of water and glycogen stores Admittedly, the glycogen use will probably be in the neighborhood of 3-400 grams for a 70 kg person - Not a lot, but enough to notice). – JohnP Feb 13 at 14:31