<p>Ok say if someone lost weight on a diet? Where does the extra weight go? I know there’s a difference between mass and weight…but when you lose weight, don’t you lose mass also? And where does the mass go?</p>
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<p>Yes, but it’s not relevant here. It’s only relevant in physics class. “Lose weight” effectively means the exact same thing as “lose mass.”</p>
<p>“Mass never changes” doesn’t mean the mass of something can’t change…it just means mass doesn’t depend on the strength of gravity like weight does. If you remove mass from something, it will lose mass, and that’s what weight loss is.</p>
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<p>My understanding is that you breathe it out. Weight loss is just your body using stored fat because you didn’t eat enough, and the products of that process are water and carbon dioxide.</p>
<p>The mass of the system never changes. But an individual inside the system can change mass as long as they receive mass or give mass to the system around them(the universe). Excretion, Exhaling, and Sweating are some ways the mass is lost for an individual.</p>
<p>When you “lose weight,” your body is breaking down the fat into simple sugars and then converting them into ATP and other “energy molecules.” Bi-products include carbon dioxide, water, and heat.</p>
<p>The reaction looks like this:</p>
<p>C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) + heat</p>
<p>So yes, mass is conserved.</p>
<p>See: cellular respiration</p>
<p>So it’s possible to lose weight by breathing more? 
Thanks for the explanations guys! :D</p>
<p>Lol. Not exactly. What breathing does is gets oxygen to your muscles. The muscles use stored fat for energy. So you need to my only breathe more but also use your muscles</p>