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Gut Bacteria and Weight Gain

Do certain intestinal bacteria cause weight gain? This week two studies show how the types of bacteria in your intestines may contribute to whether or not you become obese.

One study showed that a specific intestinal bacteria found in humans causes obesity in mice. Mice whose intestines had a lot of a bacteria called Clostridium ramosum became obese on a high-fat diet, while those that did not have the bacteria gained far less weight on the same diet (mBio, Sept. 30, 2014). Mice with the same bacteria who ate a low-fat diet did not become obese. Clostridium ramosum is far more common in the gut of obese humans. A high-fat diet promotes the growth of Clostridium ramosum (Int J Obes (Lond). 2013, Feb;37(2):216-23). So far researchers have not found any way to remove Clostridium ramosum from the human gut without also removing the healthful bacteria that protect people from disease.

How Some Intestinal Bacteria Can be Harmful
Hundreds of studies show that bacteria in your intestines regulate your immunity. Certain bacteria break down the food that you eat so effectively they markedly increase the absorption of calories from food that you eat to make you fat. Other bacteria punch holes in your intestines to allow breakdown products of the foods that you eat to enter your bloodstream and cause your immunity to attack these foodstuffs as if they were invading germs (Gastroenterology, 2000;119: 1740–1744). Escherichia coli, Klebsiella pneumonia and Streptococcus viridans have been shown to significantly increase intestinal permeability to increase risk for Crohn’s disease and type I diabetes (Gastroenterology 2000;119:1740–1744). Other bacteria such as Bacteroides, Enterobacteriaceae and Clostridium produce known cancer-causing chemicals from the food that you eat (J Natl Cancer Inst 1980;64: 255–261). The very strong association between eating red meat and colon cancer is probably caused by this type of reaction. On the other hand, good bacteria, such as Lactobacillus and Bifidobacterium, block the absorption of certain foodstuffs to protect you against invading bacteria.

Antibiotics in Infancy Associated with Increased Obesity Risk
In the second of this week's studies, researchers from the University of Pennsylvania and Bloomberg School of Public Health reviewed health records of more than 64,500 children from birth to age five. Seventy percent had received two courses of antibiotics by age two. Those who had four or more courses of antibiotics had a ten percent increased risk for being obese by age five (JAMA Pediatrics, published online September 29, 2014). Those given a broad-spectrum antibiotic (that can kill several types of bacteria indiscriminately) were more likely to be overweight, while those given narrow-spectrum antibiotics directed by a culture were less likely to be overweight.

Antibiotics can change the bacteria in your intestines from normal to those that specifically break down food in the intestines so that far more calories are absorbed. This study does not prove that antibiotics cause obesity; it only shows that antibiotics given in the first few years of life are associated with obesity.

What Does this Mean for You?
The foods that you eat determine, to a major degree, the types of bacteria in your intestines. Bacteria grow profusely on the food that they prefer to use for energy. The association of a high plant diet with decreased risk for heart attacks and certain cancers may be the result of promoting the growth of certain bacteria in the intestines. Eating a high plant diet markedly increases many of the so-called good bacteria. I also believe that you should avoid regular use of artificial sweeteners.

Probiotics and Prebiotics
Gut Bacteria to Help Treat and Prevent Cancers
Auto-Immune Diseases and Gut Bacteria

Checked 9/15/15

October 5th, 2014
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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