Name the three elements found in greatest percentage in the human body.

It may seem surprising, but the vast majority of the human body's mass is made up of just three elements. The single biggest contributor is oxygen, primarily because our bodies are mostly water. Since water (H2O) consists of two hydrogen atoms and one oxygen atom, and oxygen is significantly heavier, it accounts for the bulk of water's weight. Considering that 60-70% of the human body is water, it becomes clear why oxygen makes up such a large percentage of our total mass. Oxygen is also a critical component of all the major organic compounds essential for life and is vital for cellular respiration, the process that generates energy in our cells.

The second most abundant element is carbon, which is the fundamental building block for all of life's essential organic molecules. Every carbohydrate, protein, fat, and nucleic acid in our bodies has a backbone of carbon atoms. Carbon's unique ability to form stable bonds with four other atoms allows it to create the complex and diverse structures necessary to sustain life. Breaking these carbon bonds is also a key way our bodies release energy from food.

Finally, hydrogen is the third most common element by mass. Like oxygen, its high prevalence is largely due to the abundance of water in the body. Furthermore, hydrogen is found in every single organic molecule, alongside carbon. Together, these three elements—oxygen, carbon, and hydrogen—are the essential foundation (Review) of human composition, accounting for roughly 93% of the body's total weight.