In a desperate bid to lose weight, some people turn to habitual laxative use in the mistaken belief that it will allow them to eat whatever they want without absorbing the calories. Not only is this practice erroneous, it's potentially dangerous -- laxative use should never be considered a weight loss technique for many reasons, the least of which is the fact that it won't work.
Laxatives Don't Prevent Food Absorption
Many people think that taking a laxative after eating will force the food through the digestive system before it can be absorbed, but this isn't true. By the time the food you eat reaches the part of your intestines where the laxatives work, it has already been digested and the nutrients have been absorbed. All the laxative does is draw water into the bowel to add bulk and lubrication to the stool, and some laxatives also stimulate intestinal contractions to help move things along. Since laxatives don't affect nutrient absorption, they cannot affect fat stores. You may lose a pound or two of water, but that will come back as soon as your bowel habits return to normal.
Laxatives Cause Dehydration
Because laxatives draw water into your intestine from surrounding tissues, they can leave you at risk for dehydration. The sudden loss of body fluids can lead to water retention as your body tries to conserve every drop of moisture to keep the dehydration from worsening -- in other words, you may actually look puffier and more bloated. The rapid fluctuation of fluid levels in the body can cause your electrolyte imbalance to go off-kilter, and you may experience dizziness, fatigue, weakness and nausea.
Laxatives Can Cause Dependence
People who use laxatives in larger doses or for a longer time than recommended are at risk of developing a dependency. When you consistently stimulate your bowel chemically, your body forgets how to do it naturally, and you won't be able to have a bowel movement without laxatives. After a while, it will take a higher and higher dose to stimulate any movement at all. The "tone" of the intestines become lax because the laxatives have done all of the pushing so far, and they may become dry as they forget how to draw adequate water for lubrication. Recovery from laxative dependence is possible, but it may involve many months of chronic constipation and bloating.
You Can't Spot-Reduce
Even if laxatives did cause fat loss, it wouldn't happen just in your stomach. When you lose fat, it happens from all over your body at once. You don't get to choose which fat you lose -- in fact, the areas with the largest fat stores are usually the last ones to become thin simply because there's more stored fat to burn off. Abdominal exercises will tone your muscles, but they won't cause fat loss either -- the only thing that can make you lose fat is burning more calories than you consume. That means restricting your calorie intake and increasing physical activity.