Of course it’s all a sham. Nothing gets trapped in your colon - it’s not a sewer pipe. Just ask anyone who’s recently had a colonoscopy - and they have the pictures to prove it. Having a “blow out” won’t get rid of any fat, won’t make you any healthier and in most cases won’t even temporarily decrease your abdominal measurement by so much as a centimeter. Why?
First, a little basic biology. The colon, also called the large intestine, follows the small intestine and comprises the end of the gastrointestinal tract. Most nutrients from food are absorbed in the small intestine. The colon absorbs water and salts from the stool while it pushes it along through the rectum, which excretes it.
Laxatives and enemas, which promote bowel movements, have been around for at least 4,000 years and were famously practiced by the ancient Egyptians. That shouldn't be an endorsement; the ancient Egyptians also buried servants alive to attend to the mummified kings in the afterlife.
The golden age of the colon in America was in the late 19th century when—perhaps influenced by a new emphasis on hygiene and proper sewage removal—serious-minded doctors developed the theory of colonic autointoxication. The most famous of these was none other than Dr. John Harvey Kellogg (yes as in the breakfast cereal), and you can see his enema exploits documented in the movie “The Road to Wellville”.
The idea was that the intestines were a sewage system and that constipation, although never specifically defined, resulted in a cesspool within the body where food wastes would putrefy, become toxic, and get reabsorbed through the intestines. Some scientists also claimed that constipation caused fecal matter to harden onto the intestinal walls for months or years – 20 pounds or more worth, blocking the absorption of nutrients (yet somehow not blocking toxins). This latter claim that waste “sticks to the intestine wall like spackling on the inside of a pipe” is still made by charlatans to this day.
Constipation is indeed uncomfortable. But careful testing found that those symptoms associated with it and attributed to autointoxication—headache, fatigue, loss of appetite and irritability—were not a result of toxins but rather the colon expanding. The reason was mechanical, not chemical. A 1919 article in Journal of the American Medical Association by W.C. Alvarez, "Origin of the so-called auto-intoxication symptom" put these ridiculous ideas to rest once and for all. By the 1920s, colon cleansing was relegated to the realm of quackery.