What Happens To Fat When You Lose Weight?
Q: Ummmmm…what happens to fat when you lose weight? Does it magically transport bit by bit from my body to my worst enemy’s body? That’s definitely what I have my fingers crossed on in hope of!
A: You’d be surprised that a lot of doctors, dietitians, and personal trainers don’t know the answer either, with some thinking that fat disappears from the body by getting excreted in the feces or turning into heat or muscle. There’s a lot of confusion on the topic, so rest assured that you’re not alone in being absolutely wrong with your guess.
Yes, your guess is WRONG!!!
So what happens then?
Well, let’s first make sure we understand what fat is and how you gain it…
When you eat and take in more protein and carbs than the body can use for energy or its other immediate needs, the surplus gets converted into triglycerides, which are a type of fat, and then stored inside fat cells in adipose tissue. Dietary fat from food is also stored in fat reserves but instead of undergoing conversion, the macronutrient gets broken down into its component fatty acids and reassembled into triglycerides.
Fat cells increase in size and number as more triglycerides have to be stored from the overconsumption of calories, which results in weight gain and your body getting bigger from the buildup of adipose tissue. Reversing that action requires a calorie deficit, which is when you burn more calories than you consume so the body is forced to tap into the triglycerides in storage and convert them into energy to make up for what it’s no longer getting from food to perform its vital functions and additional tasks.
Whether a calorie deficit occurs by reducing food intake or increasing physical activity, stored triglycerides get broken down into free fatty acids and glycerol when energy is needed. After the process of lipolysis takes place to mobilize fat, the next step is fat oxidation, which is when the free fatty acids are transported to the mitochondria where they’re burned to produce fuel that the body can use to power itself.
Lipolysis is how the body takes triglycerides out of storage in the fat cells and fat oxidation is how that released fat is converted into usable energy. Carbon dioxide and water are the waste products of the metabolic process of stored energy conversion. So what happens to fat when you lose weight is that after it’s used as energy, the overwhelming majority of the waste is breathed out from the lungs as CO2 while a little bit of the waste is excreted as H2O via bodily fluids.1More precisely, the figure is 84 percent carbon dioxide and 16 percent water. That means that if you want to lose 10 lbs of fat, then you need to inhale 58 lbs of oxygen, which will produce 8.4 lbs of CO2 that will leave your body by exhaling and 1.6 lbs of H2O that will do so through sweat, tears, urine, and water vapor during respiration.
Basically, fat loss results in the fat cells shrinking in size but not number as their contents turn into energy and waste, most of which is exhaled and either feeds plants as part of photosynthesis or contributes to global warming.
Now, does anyone else have a fitness or nutrition question of their own that they want to ask?
Glossary: adipose, caloric deficit, calories, dietary fat, fat, fitness, food, macronutrients, muscle, nutrition, personal trainer
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