We give this age-old question the popular dinner party game treatment. This is where your fat really goes when you lose weight.

It’s a happy day when you start to see the numbers tick lower on your scale. But have you ever stopped to consider where the fat actually goes? Researchers at UNSW School of Biotechnology and Biomolecular Sciences in Sydney, Australia did. Here we reveal their findings in a round of Two Truths and Two Lies (because two lies are more fun than one)!

Can you spot the two lies below?

#1 Fat turns into muscle.
#2 Fat disappears into thin air.
#3 Fat is converted into heat.
#4 You pee the fat out.


Lie: Fat turns into muscle.

Fat and muscle are made up of two entirely different types of tissue; fat is adipose and muscle is protein. That means no matter how many salads you eat or squats you do, fat will never turn into muscle. You may think this is the case if you’re exercising, because you do burn fat as fuel during aerobic workouts and you may also be increasing your muscle mass through weight lifting. Then as you start to lose weight, your muscles may seemingly come out of hiding and become more pronounced as you shed the layers of fat. But it will never, ever turn into muscle.

The good news is, if you start to lapse on your diet and exercise program, muscle won’t turn into fat either.

Truth: It disappears into thin air.

Most of the weight you lose is converted into carbon dioxide and you exhale it out of your system. The researchers found that when you eat more carbs and proteins than you expend calorically, they are converted into triglycerides. The triglycerides are then stored in lipid droplets inside your fat cells. When you lose weight, you need oxygen (while burning lots of calories) to break down the triglycerides to access the carbon dioxide. The study found that in 10 kilograms of “lost” fat, 8.4 kilograms are exhaled as carbon dioxide through your lungs.

Lie: Fat is converted into heat.

If you picked this one as the truth, you’re in good company: more than half of the doctors, dieticians and personal trainers in a survey conducted by the study’s authors believed this to be true. But it’s physically impossible and violates the Law of Conservation of Mass.

Truth: You pee it out.

The remaining 1.6 kilograms of the “lost” fat become water and are excreted via urine, sweat, tears, breath and other bodily fluids.

Looking for help eating better and losing weight? A primary care physician can help you create your weekly meal plans for optimal health.

If you are in the Los Angeles area and are looking for exceptional care from some of the top physicians in the world, be sure to schedule an appointment by calling (800) USC-CARE (800–872–2273) or by visiting http://www.keckmedicine.org/request-an-appointment/.

By Anne Fritz