Magnesium citrate is an over-the-counter laxative commonly used for bowel preparation before a surgical procedure or to treat constipation. Magensium citrate is not the doctor's first choice for constipation, unless it is severe; fibers, stool softeners or plum juice are usually used since they are softer.
Magnesium citrate can cause temporary weight loss due to the intense diarrhea it causes. The loss of weight is due to the loss of water and the contents of the large intestine. After the person returns to normal eating and bowel habits, the weight returns to normal easily because very little or no fat was lost. Most of the calories in the food are absorbed in the small intestine and stomach before entering the large intestine where the laxatives act.
If you are using magnesium citrate or other laxatives as a method of weight loss, you should stop them immediately and consult a doctor or dietitian. If you have trouble stopping yourself, you should have an eating disorder evaluation. The abuse of laxatives causes loss of fluid, electrolytes and minerals and can cause severe dehydration, kidney failure and liver damage.