What Happens to the Fat When I Lose Weight?

By: Scottsdale Weight Loss Center

Published: September 17, 2025

Call for a Consultation

A smiling, fit woman in a sports bra celebrating her body transformation in her old, baggy pants.

How to Preserve Muscle During Weight Loss with Protein

Jul 1, 2026

When most people try to lose weight, they watch one number: the scale. But not all weight loss is...

Please Don’t Drink Your Calories if You’re Focused on Weight Loss

Apr 28, 2026

Liquid calories are fluids consumed as part of your daily diet that often go unnoticed and...

Rock Climbing: Lose Weight on the Wall

Apr 28, 2026

If your weight loss efforts have hit a wall, why not climb it? Rock climbing is becoming an...

Weight Watchers vs. Medical Weight Loss Programs in Scottsdale: Comparing the Results

Apr 28, 2026

Many residents in Scottsdale, Phoenix, and Glendale struggle with weight loss plateaus despite...

Arizona Medical Weight Loss Programs vs Online Programs: Which One Provides the Best Results?

Mar 25, 2026

The weight loss landscape has shifted significantly with the rise of digital health platforms....

Is Brown Rice Healthier Than White Rice?

Feb 27, 2026

Is brown rice better than white rice? Intuitively, one would think that brown rice is much...

« Older Entries

Return To Blog

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.

nick weight loss before and after scottsdale weight loss center

Nick's Story

"I wish I would have come here first. We spend all our time reacting to the next great weight loss tip or program. It might work for a while, but does not last and we end up yo-yoing from one fad to the next – as we gain more weight." Read More

gina weight loss before and after scottsdale weight loss center

Lost 44.5 lbs

"I had no trouble adhering to the meals and they really helped catapult my progress! The classes were so beneficial to me because they helped change my thinking about how I viewed health, nutrition, and fitness.

I will always have my relationship with Scottsdale Weight Loss Center. They truly helped me change my life forever." Read More

lauren weight loss before and after scottsdale weight loss center

Lost 60 lbs

"Dr. Ziltzer and everyone who I have come in contact with at the Scottsdale Weight Loss office have been so encouraging and I look forward to seeing them each week. It is now a year and 2 months later since I started. I am down 60 lbs., which is the average amount a 9-year-old weighs, it is crazy to think I lost a whole person! I feel amazing, I hit my goal weight in November 2021 just before Thanksgiving. Nothing on my body hurts anymore..." Read More

chuck h weight loss before and after scottsdale weight loss center

Lost 66 lbs

"The best thing I did was call the Scottsdale Weight Loss Center. I have a lot more energy, I'm not hungry, and it feels great.

You can take it from me that this is a program that produces results. The staff is always positive, supportive, and never judgmental.

Your visits always result in positive reinforcement, no matter if you had a good week or a bad week." Read More

emily weight loss before and after scottsdale weight loss center

Lost 101 lbs

"Here I am at the lowest I have been since high school weighing in at 155lbs. I have lost 101 lbs, BMI of 39 when I started, to 21.6, and of course at body fat % of 47.1 to 26.5%. I told myself by my 30th birthday I wanted to be confident in the way I look and I owe it all to SWLC. The entire staff is so welcoming and they are rooting for you just as much as you are rooting for yourself...." Read More

Reviews

      Excellent rating  
 Based on 420 reviews 
    
  
 
 
     Trustindex verifies that the original source of the review is Google. Diana is the Best!!
     
   Sara M 
 12 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. Great place 30 lbs.and counting thank you
And now it is over 40 lbs. and counting thank you great job
     
   John J 
 29 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. Best of the best - Dr. Z !!
     
   Mar S 
 33 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. The Biltmore location is top notch! Everyone there is so very friendly, professional and makes the experience so personal and easy. Highly recommend!
     
   Sue M 
 35 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. This practice is everything you would want from a physician office. Professional and knowledgeable staff and caring providers 10 stars!!!!
     
   Lisa Y 
 41 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. Everything perfect
     
   Andi K 
 46 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. I landed at Scottsdale Weight Loss 13 years ago and lost 50 pounds….regained 10 and then lost them again, plus another 20.  It is a great program, and all the professionals are amazing and caring.
     
   Mj W 
 53 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. SWL has been a God send to me! Dr. Guzman & staff especially Lilia & Bianca! They’re so supportive & professional I have lost approx 50 pounds over the year at my own pace.
     
   Donna L 
 55 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. The staff at the Phoenix office are great! My experience with Dr deGuzman has been wonderful. Miriam has always been very helpful and makes the office visits pleasant and personal. The medical assistants have always been professional and great to help meet my goals.
     
   Paula S 
 81 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. I really felt comfortable with Kristen at my initial appointment.  Everyone at the center was caring and friendly, from Bianca, at the front desk, to Lily, who is the MA.  Kristen listened to my frustrations and prior disappointments about what has not worked, and is confident that she can help me achieve my goals of weight loss.  I am looking forward and excited to see the success I will attain.
     
   Joyce K 
 88 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. Amazing staff and great program!  Feeling great!
     
   Brian H 
 92 days ago
 
 
 
 
   Trustindex verifies that the original source of the review is Google. I'd lost 20 pounds on my own and struggled to keep it off.  I decided GLP-1 meds were the next step in losing more and keeping it off.  I wanted a medical doctor supervised program and chose SWLC.

I am so very glad I did!  The team in Glendale is so supportive and kind; and when I feel discouraged, they pick me up with positive energy and input.  They really do a great job with encouragement all the time.

6 weeks in I've lost 17 pounds, and am approaching weight loss with a very new perspective.  Also knowing that when I reach my target goal, they'll be there through maintenance and beyond is encouraging as well.  Good to not feel alone on this journey.
     
   Stephanie P 
 105 days ago
 
 
 
 
 
 
  
 
 
 
   Verified by Trustindex  Trustindex verified badge is the Universal Symbol of Trust. Only the greatest companies can get the verified badge who has a review score above 4.5, based on customer reviews over the past 12 months. Read more