The truth about laxatives for weight loss

What are laxatives?

In general, laxatives are a class of drugs that help make bowel movements easier for people, typically only taken short-term for constipation. (1) They typically work either by stimulating the bowels/digestive system, or by manipulating stool in some way, making it easier to pass.

There are several different types of laxatives, which all work in specific ways, including: (1)

• Lubricant laxatives: Coat the lining of the intestines as well as the stool to help things move along more easily.
• Bulk-forming laxatives: Absorb excess water in the intestines and add bulk to stool in order to push things along.
• Stool softeners: The opposite of bulk-forming laxatives, these help stool absorb more water, making hard stool easier to pass.
• Stimulant laxatives: Causes the muscles of the large bowel to contract, forcing stool out 
• Saline laxatives: Help draw water specifically into the small intestine to help stimulate bowel movements.
• Osmotic-type laxatives: Help the colon retain more water to encourage more frequent bowel movements.

Typically, people will take these types of medications to help with constipation, a condition caused when bowel movement becomes infrequent and/or painful. However an increasing number of people have started abusing laxatives as an attempted weight loss strategy.

How long does it take for laxatives to work?

In general, laxatives are relatively fast-acting medications. How long it takes laxatives to work depends on the specific type of laxative being used, as well as the ingestion method.

Stimulant laxatives typically work the fastest, kicking in anywhere from 6-12 hours after taking an oral dose. Stool softeners generally start working within 12 to 72 hours. The effects of bulk-forming laxatives can sometimes be seen within 12-24 hours, though typically, that class of laxative needs 2-3 days to achieve its fullest effect. And osmotic laxatives generally take between 2-3 days to work. (2)

Do people use laxatives to lose weight?

Many laxatives work by drawing water from different parts of the body into the large intestine, in order to create either lubrication, softer stools, or stimulation. When this stool is expelled, the body also loses the water that was redirected into the intestines. 

Losing water through laxative use may result in a temporarily lower number on the scale, however, it doesn’t stay off. The weight returns as soon as the person takes a drink, or the body rehydrates. In addition, choosing not to rehydrate can have its own detrimental impacts on the body. 

By the time laxatives kick in, the small intestine has typically already had the time to absorb the calories from any food that has been consumed, with the resulting effect merely pushing out redistributed water, plus the bulk of any indigestible fibers in the intestines and any waste already in the colon.

For these reasons, abusing laxatives does not result in weight loss beyond temporary reduction in body water, and this disordered behavior can cause substantial health consequences.

Other effects of laxatives

Occasional laxative use to help with genuine constipation or other medical problems can be relieving and appropriate, but habitually abusing laxatives can lead to a number of health issues.

Dehydration

As many laxatives work by pulling water from other areas of the body into the intestines, many of these medications can also lead to dehydration, a condition which can range from uncomfortable to dangerous.

Milder dehydration may manifest as headaches, fatigue, dry skin, dizziness, or reduced urine output. (1) But depriving the body of too much water for too long can have more serious consequences, including rapid heartbeat and breathing, an altered mental state, and cold, clammy skin. Severe dehydration is a very rare effect of laxative abuse, but considered a medical emergency in general, and could even be life-threatening. (3)

Electrolyte imbalance

Electrolyte imbalance is another common impact of laxative use or abuse, once again due to the amount of water and fluid being dispelled from the body by the medications. (1)

Electrolytes are important minerals and nutrients that dissolve in bodily fluids to be more easily absorbed by the body. They are essential to the healthy functioning of key organs, as well as a number of other regular bodily functions.

An imbalance of electrolytes can cause a number of milder effects, including thirst, weakness, muscle aches, fatigue, headaches, and heart palpitations. But the condition can also be much more serious, leading to confusion, seizures, or even coma if the imbalance becomes severe and sustained enough. (1)

Dependency

While few studies have been conducted on whether people can develop a dependence on laxatives, there is some anecdotal evidence to support the idea that people who habitually abuse laxatives, particularly stimulant laxatives, may use them to help with bowel movements. Dependency on laxatives can cause the inverse effect of relying so much on them that when discontinuation is achieved, an individual actually becomes constipated.

Habitually using laxatives—especially when there is no true medical need—can be a dangerous practice, resulting in potentially severe effects of dehydration and electrolyte imbalance. And over-using laxatives has also been tied to a number of other dangerous health risks, including gastrointestinal damage, liver damage, and kidney failure. (1)

Laxatives and disordered eating

Many people struggling with any eating disorder, but most commonly in bulimia nervosa turn to the misuse of laxatives as a compensatory behavior after eating. People struggling with the purging type of anorexia nervosa are also at a heightened risk of misusing laxatives. 

One study found that at least four percent of the general population participates in laxative abuse. (4) 

If you or someone you love is misusing laxatives, it’s important to seek out appropriate information on treatment and recovery options. Reach out to our clinical team at Within if you are using laxatives while experiencing an eating disorder. Help is available now.