Antibiotics and weight gain?

Last week I announced that, knock on wood, I haven’t got sick this year. This time of the year usually everyone in my practice is sick and guess what? My body usually gives up around October and I get sick and this year I survived until the day I announced it loud. Two days later I woke up with sore throat and I did a quick strep test and (boom!) just like that, I needed antibiotics after almost four years.

I hate antibiotics for so many reasons. One of the big ones is I always balloon up after taking them. For the longest time I was sure this is my body’s unique and stupid reaction to antibiotics. However, since I started practicing, I see that many people with stalled weight loss or sudden weight gain have a past medical history of taking antibiotics within 3-4 months period prior to weight management problem.

Yes you heard me right: antibiotics are linked to weight gain and obesity!

Look around you!

Obesity is an epidemic in North America. Research suggests that there is a link between antibiotic use and weight gain. It is wise to give it benefit of doubt as we are exposed to antibiotics on a daily basis through our food. We give it to our children for every single earache or sore throat and the story goes on and on. I am not going to even start talking about how many people I know who are taking them for acne.

Let’s use our analytical mind for a second. Chickens are fed antibiotics to get fat. Right? So, lets do the math. It can have the same effect on us as well. Kudos to Dr. M. Blaser for putting these pieces together. This is a simple fact that we ignored as a society for the longest time.

Let me break it down for you:

Human gut:

Your gut is full of bacteria. These bacteria are responsible for breaking down nutrients in your body, reducing inflammation and helping with caloric absorption. Now when you take antibiotic all these good bacteria die. Antibiotic does not select to kill bad bacteria only. If there is a bacterium anywhere, it will kill it

So what does antibiotic have to do with weight gain?

Research shows that antibiotics change the gene expression of gut bacteria. This means that genes related to converting carbohydrate to short chain fatty acids (in other words fat) get activated more, As a result you accumulate fat.

In 2013, International journal of obesity published an article indicating that children, who had antibiotics within first six months of life, have more tendencies to become overweight by age three.

Now let’s quickly talk about physiological effect of antibiotics that leads to weight gain:

Gherlin is your hunger hormone that after each meal it falls down and sends signals to the brain to stop the eating process. Gherlin and your belly fat have a very strong connection. Researchers found that there is almost a 6-fold increase in Gherlin level 1.5 years after using antibiotics. This means good luck stop eating! Fat tissues produce a hormone called Leptin. When you gain weight, extra fat means extra Leptin to warn the brain to stop storing fat. Problem is when there is too much Leptin in your body, your brain becomes desensitized to it and you become Leptin resistant. This means accumulating more fat as the inhibition is gone. Interesting enough antibiotics increase Leptin to the point that you become Leptin resistant so you store fat. Food is converted to energy via mitochondria. In other words mitochondria burn calories. There is growing evidence that antibiotics damage mitochondria and cause weight gain.

That’s not all!

Look at Standard American Diet (SAD diet), which practically means close to 50% carb and 35% fat. Now if more of these carbohydrates are being converted to fat because of antibiotics, are you surprised that you definitely know someone around you with obesity, diabetes, heart problem and cancer?


Usually after I explain these points to my patients, I get challenged. I am pretty sure some of the questions my patients ask are on your mind as well:

“Oh! Dr. Z, you are basically telling me not to ever take antibiotics?”

No! I cannot imagine life without antibiotics. However, reserve antibiotics for serious infections only and do not take it for every single cold or flu. We have used antibiotics so much in North America that the bacteria are becoming resistant to antibiotics and if god forbidden we are hit with a very serious resistant infection, we might pretty soon run out of antibiotic options because at some point bacteria will stop responding to even the strongest antibiotics we have available.
Remember: DO NOT ELIMINATE antibiotics, but USE WITH CAUTION!

“Dr. Z you are just paranoid for no reason. I will take my probiotic and I will be fine”

Yes! probiotics are essential but there is growing evidence that there are so many bacteria in our body that we do not even know they exist and with antibiotics they are going extinct. Probiotics are a good prophylactic measure to take. However, are they enough? We simply don’t know. We just know they are better than nothing.

“Listen Dr. Z, all this research you are talking about was done on mice. Mice are not human”

This goes without saying that mice are different, but there are many similarities as well. What makes it worthwhile to take antibiotic and gut bacterial health serious is, in a study published in October 2014, researchers found that 32 percent of children who had antibiotic before age of one were obese compare to 18 percent of those without early antibiotic intake. This doesn’t mean that if your child is exposed to antibiotics in early life, he/she would definitely be obese as an adult. It simply means that his/her risk of obesity is higher than someone with no early childhood antibiotic exposure.

Fine Dr. Z, I will do my best to avoid antibiotics and preserve my gut bacteria. Are you happy now?

Are you happy now?

Antibiotics are not the only factor affecting your gut bacteria’s health. Too much sugar will shift your gut bacteria from being beneficial to yeast over-dominance Food is a major antibiotic exposure route. Make sure you buy organic meat with no chemical and antibiotic

Bottom line is:

Preserve your gut bacteria in any way possible. Reserve antibiotics for serious infections only Choose your food wisely Take your probiotics

I hope next time you or your little one come down with a cold/flu, you will take the time to think twice before using antibiotics. Send me your questions and I will happily add them to this blog post with an answer.

Author resumes no liability for incorrect information or any action reader decides to take based on the information on this blog post. This blog post is only author’s personal input on the topic and by no means entails any medical advice.