Question

why lack of iron in our diet leads to low energy levels of the body

Answer 1

Let me make this simple
Our blood had hemoglobin which carries oxygen and has iron content in it. When iron content decreases, the combining capacity of hemoglobin with oxygen also decreases. So our body gets less amount if oxygen than we actually need. So we feel dizzy and weak

Answer 2

Iron deficiency can stop your main function that you aren't able to produce enough oxygen carrying red blood cells.

Therefore your body struggle to transport oxygen to your internal parts like brain, tissues, muscles and cells, and you feel exhausted and weak.

An iron deficiency can lead the diseases like Anemia.