Some interesting thoughts…

The significant adverse long and short-term effects of obesity have been extensively studied and are well known. The World Health Organization (WHO) states that childhood obesity is one of the most serious health challenges of the 21st century. The WHO further state that childhood obesity, as well as their conditions, is largely preventable and this subject therefore needs higher priority in the healthcare system globally.

Many studies have therefore evaluated the effect of antibiotics on the child’s developing gut. Did you know that globally, low-dose antibiotics have been administered to promote growth in the agricultural industry since more than 50 years? Studies have been done on young mice where they were given small amounts of antibiotics, not enough to treat any diseases. What they found was astonishing: not only did the antibiotic administration lead to weight gain in the young mice, but it also substantially changed their microbiome and increased hormone levels.

This got researchers to look into what antibiotics, that are so widely prescribed to children, do to children’s gut bacteria and whether that has an effect on their weight.

Many recent studies show that antibiotics disrupt the normal maturation of the child’s microbiome, which are their intestinal bacteria communities that are responsible for healthy digestion and energy uptake from the food we eat.  Also, a large body of research suggests that children who were exposed to antibiotics have a mildly increased risk of obesity and/or being overweight later in life.

However, none of the studies could determine a clear cause for this. It has been speculated that it is the repeated use of antibiotics that may have an impact on intestinal flora, the microbiome, that alters metabolism function.

 The different studies found that it is the cumulative effect of the antibiotics that seem to have the biggest effect on the risk of later-life obesity. Also, some of the studies suggest that earlier antibiotic exposure has a stronger effect than later exposure. This might be due to the incomplete maturation of the child’s microbiome.

It is really important to notice, that not all antibiotics are the same! So called “broad spectrum antibiotics”, that are effective against a broad range of bacteria, have a much greater effect on the risk of long-term obesity than “narrow-spectrum antibiotics” (only acting on a narrow range of bacteria) and penicillin.

Interestingly, some studies found that boys appeared to be more affected by antibiotic use below the age of 24 months than girls. Why that is, we don’t know yet.

If obesity and the risk of being overweight was a simple matter of evaluating more carefully when prescribing antibiotics, the problem would be fairly simple. Nevertheless, the risk of obesity and weight gain is affected by a complex mixture of physiologic, environmental, socio-economic, and medical factors.


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World Health Organization (WHO), 2019b. Childhood overweight and obesity [online]. Geneva: WHO. Available from: [Accessed 16 Aug 2019].