Final answer:
Potassium is the electrolyte commonly lost during metabolic alkalosis, often due to severe vomiting, use of diuretics, or excessive antacid intake.
Step-by-step explanation:
The electrolyte commonly lost when the body is in metabolic alkalosis is potassium. This condition can be caused by severe vomiting, which leads to a loss of hydrogen and chloride ions, or through the use of diuretics, which causes the body to lose potassium ions. An excessive intake of antacids can also contribute to alkalosis by causing an excess of bicarbonate in the blood. Conditions like Cushing's disease can cause chronic metabolic alkalosis through elevated aldosterone levels, leading to potassium loss in urine.