A common question I hear in clinic is: “When I lose weight, where does the fat actually go?”
Some common misperceptions include:
- Fat turns into For the chemistry enthusiasts out there, this would violate the law of conservation of mass.
- Fat turns into muscle. This would be ideal, but unfortunately it’s
- Fat leaves the body in bowel movements. Not true
Don’t worry, many health professionals are surprised by the real answer as well.
So where does the fat go?
The truth is that fat is converted to carbon dioxide and water. You exhale the carbon dioxide through your lungs, while the water enters your bloodstream and is eliminated as urine or sweat.
Here’s a surprising fact: if you lose 20 pounds of fat, 16.8 pounds leaves your body as carbon dioxide and 3.2 pounds leaves as water. This means nearly all of the weight you lose is literally breathed out. Amazing!
This process isn’t unique to fat. Nearly all carbohydrates, alcohol, and dietary fat you consume are ultimately broken down the same way, into carbon dioxide and water. Protein is similar, with the exception of a small amount of nitrogen containing components that are excreted in urine. The only real exception is fiber, which passes through undigested and leaves the body as stool.
One of my patients once asked me: “If fat turns into carbon dioxide, does that mean losing weight contributes to global warming?”
No, it does not.
Be well.
About the Author
John V. de Guzman, MD, is a board-certified physician specializing in obesity medicine and weight management at Scottsdale Weight Loss Center. With 11 years of clinical experience helping patient achieve safe, and sustainable weight loss results, Dr. de Guzman combines medical expertise with a compassionate, individualized approach to care. His focus on evidence-based strategies empowers patients to better understand how the body works and to make lasting, healthy lifestyle changes.
Questions? Please contact the weight loss experts at scottsdaleweightloss.com
