Coolest fact: Starts with trees: Ever wonder where their mass comes from? The General Sherman tree, for example annually puts on the mass of a large oak tree every year.
'where did it get its mass, its thick trunk, its branches?' — the instinctive answer would be from the soil below, plus a little water (and, in some mysterious way, sunshine), right?From here: "Would it surprise you, ... to discover that 95 percent of a tree is actually from carbon dioxide, that trees are largely made up of air?" You can measure their carbon sequestration in pounds, baby.
The inputs to a tree are soil-minerals+sun+CO2. the outputs are O2. The growth in a tree is the difference between CO2 and O2's the tree breathes. For humans, it's different - in fact opposite. The inputs to humans is food+water+sun+O2. The outputs are CO2+waste products.
Humans gain weight through food, and lose it through exhaling.
Consider this: All other factors held constant, the weight loss attributed to exercise is largely the CO2 you're outputting compared to the O2 you're inputting. Exercise makes you breathe faster/harder.
If you're packing on a few extra pounds, breathe yourself thinner.