Are Antibiotics Making You Fat?

From looking at US farm practices, we know that antibiotics are harmful to young animals. They alter the gut microbiome and cause genetic changes that lead to faster growth.

Do antibiotics have the same effect on humans? Are antibiotics able to make you fat?

Martin M Blaser MD says they do. Dr. Blaser, the Director of the Human Microbiome Program at NYU, was the President of the Infectious Diseases Society of America and served many advisory roles at the National Institutes of Health.

Dr. Blaser’s recent book, “Missing Microbes”, provides a compelling review of the most recent research regarding the long-term consequences of antibiotic use. It is a compelling book I recommend to anyone concerned about antibiotic resistance’s alarming rise.

The book asks the poignant question if giving antibiotics to children in therapeutic doses is the same as giving them low-dose antibiotics in their livestock feeds to make them fatter. Given the rising obesity rates in Western and Asian children, this is an important question.

Researchers conducted a 2007 study under Dr. Blaser and found that mice treated with sub-therapeutic antibiotics (STAT) increased their body fat by 15% compared to control mice. Blaser believes that the mice increased bone mass along with better nutrition and hygiene antibiotics. This may have contributed to Blaser’s theory of why humans generally grow taller. More bone formation early in life means that people (or mice) will grow taller, wider, and more muscular.

Researchers then attempted to figure out why mice gained more fat. The researchers suspected that it was due to changes in the microbiome of the mice’s guts due to the antibiotics. They took samples of the poo from mice and found shocking results.

The mice had different microbial populations than the control mice. This was expected since antibiotics kill bacteria. It turned out, however, that antibiotics had altered the functions of the bacteria left behind.

Part of what you eat when you eat food is taken to the colon. It is here that the resident bacteria can get additional calories from the short-chain fatty acids (SCFA). SCFA provides energy for the colon cells and helps maintain a healthy lining.

The researchers found that the STAT mice had significantly higher levels of SCFA than the control mice when they measured their levels. The STAT mice became fatter due to increased calorie changes in microbial function.

The study also examined the liver of the mice and discovered that there were some changes. The STAT mice liver increased the expression of several genes involved in transporting fat around the body.

Next, the STAT mice were used in a second phase. This time, they were fed a high-fat, high-calorie diet similar to what most children are exposed to. Even more disappointing were the results. The results were even more depressing. Mice that had received antibiotics earlier gained 100% more fat in females and 25% in males. Worryingly, the effects had lifelong consequences, regardless of whether antibiotics were given for 4 weeks, 8 or 28 weeks.

What about antibiotics for children?

Jan Blustein and Leo Trasande analyzed data from the Avon Longitudinal Study of Parents and Children in Britain (ALSPAC). This study, which began in 1991 and analyzed data from more than 145,000 pregnant women, collected information about all babies born to this cohort over the next 15 years.

The researchers found that almost a third of the children had received antibiotics within the first six months of their lives and that the age treated was three-quarters of two. These were the results. The scientists discovered that babies who were given antibiotics within the first six months of their lives gained more weight after accounting for factors like a weight at birth, mothers’ weight, and differences between breast- and bottle-feeding.

While more research is needed to confirm these findings, I strongly recommend that you only use antibiotics when necessary. Instead, treat common childhood respiratory infections with herbs and homeopathic while a qualified practitioner supervises.

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