Where Does Fat Go When We Lose Weight?

Where Does Fat Go When We Lose Weight?

Obesity rates and the overweight population are on the rise and researchers are trying to understand why this is happening and how we can reverse this trend. Despite all the attention and research going toward lowering the rate of obesity, there’s still confusion among experts and the general public about metabolism, how your body processes food, and the biological process of weight loss.

When we lose weight, where exactly does all the fat go? It’s important that we know the answer to that question, because the answer provides the key to fighting obesity. This knowledge can help us build more tools and educational programs to better understand how our bodies work. And when we understand how fat is really stored and burned, we have more control in our weight management efforts.

Popular Myths about Fat During Weight Loss

Most people don't know what happens to fat during weight loss, but there are common misconceptions about the process. The popularity of these ideas can come from a number of places, including unqualified research on the internet, a misunderstanding of explanations given by medical professionals, or unsubstantiated word of mouth. The most common include:

  • Fat is converted to muscle.
  • Fat is converted to energy or heat.
  • Metabolites (byproducts) of fat leave the body through the excretory system.

The Real Story

When your body doesn’t use up all of the calories you’ve consumed in your diet, the extra calories get stored as fat. Excess carbohydrates and protein are converted into triglyceride, a type of fat found in your blood. Triglyceride is then stored in lipid droplets of fat cells, called adipocytes. Excess dietary fats are more easily stored and don’t require any conversion aside from lipolysis, in which lipids are broken down to release fatty acids. People who wish to lose weight are attempting to metabolize the triglycerides that are stored in their fat cells. In other words, they’re trying to use up and break down fats so that less gets stored in their bodies.

Lifting the Veil on Weight Loss

At rest, an average person who consumes a balanced and varied diet, exhales a certain amount of carbon dioxide every minute. This same person exhales double the amount when he or she is awake and performing everyday activities. Exercising releases seven times the amount of carbon dioxide! Ultimately, the lungs are the primary excretory organ of fat and losing weight requires unlocking the carbon that is stored in fat cells.

While weight loss is not a perfect science, we can all agree that it’s important to keep moving. The more active you are, the more carbon dioxide you exhale, which is how fat exits your body. However, consuming excess food easily hinders weight loss efforts, even with physical activity, because the caloric intake of food offsets the amount of carbon dioxide that gets exhaled.

So, remember to combine your exercise routine with healthy, portioned meals so you’ll have more control over your weight and your health!

Registered Dietitian, Certified Specialist in Sports Dietetics, Triathlon Coach

Comment by KayeStar
August 28, 2016
This article was confusing. I don't regard myself to be a total novice when it comes to weight loss but this left me feeling stupid.
Comment by JohnJ
June 30, 2016
What about sweat and urine. When we ecercise and use energy water is released. That is weight loss also. So when I run, some of the fat gets broken down into sugars which my muscles use and a by product is water. This is the opposite of photosynthesis where co2 is combined with water to produce sugsrs.
Jennifer - I found you're article somewhat opaque because you jumped from fat to carbon dioxide without explaining the connection. You did say later that losing weight requires unlocking the carbon from fat, but there was nothing about the mechanism. So it just sounds like another weird weight loss theory. I recommend you include that mechanism so that readers understand how it works. I think it's something like this - Fats are organic molecules mainly built from Carbon, Hydrogen, Oxygen and Nitrogen. To lose total body fat the fat molecules must be broken down to their component parts. Carbon and oxygen combine into CO2 (carbon dioxide), which we breathe out - as you say. The rest of the oxygen and hydrogen combine into H2O (water - I think most people know how we get rid of that). The nitrogen, I guess, gets exhaled with the carbon dioxide. Is this correct? You say earlier in the article that the belief a lot of people have that 'Metabolites of fat leave the body through the excretory system' is wrong. But surely that's misleading. I don't think most people would word it that specific way. I think they would word it more like 'fat breaks down into component parts that then get excreted from the system' - And surely this is exactly what happens. Your statement appears to assume that the average person is familiar with the difference between elements and 'metabolites'. I don't know the difference. I don't even know if there is a difference. And I'm guessing that, organic chemists aside, neither do most of the public.
Reply by Lighthearted1
August 27, 2016
I don't know if all you say here is accurate, but I agree. The author's jump left me, the reader, wondering what the heck? thanks for your reply.
Thank you for this detailed overview and response. We try to keep our articles simple for our readers, too much science can be overwhelming especially when we start talking about the mechanisms of metabolism. Many our readers want an overview of health from credible sources. I agree that metabolites should be defined, we will go ahead and make that adjustment. Thank you for your feedback.
Thanks for sharing such an amazing and informative article.
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