Sweat is about 99% water. The remaining 1% is made up of electrolytes and tiny amounts of minerals:
Losing water through sweat is one of a few reasons your body weight can fluctuate throughout the day.
If you weigh less after you exercise, it does not mean you’ve lost fat. It means you’ve lost water (through sweating) and need to replace the water you’ve lost.
Source: Williams, M.H. 2005 Nutrition for Health, Fitness & Spor (7thec.). Boston: McGraw-Hill Higher Education. ACSM Position Stand: Exercise and Fluid Replacement Beth Stover and Bob Murray. Drink Up! The Science of Hydration. ACSM’s Health & Fitness Journal. March/April 2007
The same is true if you lose weight after sitting in a sauna or after getting a body wrap. The weight you lose is not from fat, and will come back once you rehydrate. How to stay hydrated.
About the Author
FitnessforWeightLoss.com was created by Stephanie Averkamp, a recognized health and fitness professional and sole-author of the content on this website. Stephanie's approach to weight loss emphasizes making small, realistic, and permanent lifestyle changes. Read more...
Our Approach: Short-term solutions (like dieting) are unrealistic and ineffective because at some point they end. As soon as a diet or program ends, so do the results. Permanent weight loss is a journey; it's not a race or competition and there is no finish line. Read more...