Do Antibiotics Cause Weight Gain? Experts Weigh In

Antibiotics Affect Gut Health

"Although now banned, for years sub-therapeutic doses of antibiotics were added to animal feed to promote weight gain of livestock," explains Pat Salber, MD, founder of The Doctor Weighs In. "In fact, it has been estimated that more than half of antibiotics produced and sold in the United States prior to the ban were used as an animal feed additive. Although it wasn't clear how antibiotics were having this effect in animals, we now know that antibiotics have important effects on the billions of bacteria that live in the gut, including the guts of humans. And we know that these bacteria, collectively known as the microbiome, have significant effects on energy homeostasis and control of weight."

Salber continues, "With respect to the latter, early research found that healthy lean people have a gut microbial population that is highly diverse with many different types of bacteria. Obese people, on the other hand, have less diversity with only a few dominant species of bacteria. These studies seem to confirm that the microbiome is important in the regulation of weight, but they do not answer the question of whether antibiotics cause weight gain."

Antibiotics Can Cause an Overgrowth of Bad Bacteria

"Antibiotics cause destruction of digestive flora and bacterial imbalance, one of the most common causes of bloating," explains Christopher Calapai, DO, a board-certified osteopathic physician in family medicine, anti-ageing medicine, and chelation therapy. "Additionally, antibiotics can cause a change in bowel habits and food and nutrient absorption, which may cause you to feel tired or weak."

Calapai stresses the importance of not overusing antibiotics: "If mistreated, antibiotics can damage intestinal bacteria, and that translates into metabolic changes. They can damage mitochondria, which affects your weight because mitochondria's main job is to convert food into energy. Antibiotics can also increase blood levels of the ghrelin, which is a strong appetite stimulant."

Roshini Raj, gastroenterologist, doctor of internal medicine, and founder of the probiotic-based skincare line Tula agrees. "Antibiotics are a class of drugs that are meant to kill infection-causing bacteria," says Raj. According to Raj, antibiotics generally also kill off many healthy or good gut bacteria, which can throw the digestive system off balance and allow an overgrowth of bad bacteria that may cause people to gain weight.

Bad gut bacteria can induce cravings, hunger, and inflammation as well as increase the amount of energy it takes for your body to digest food, potentially resulting in a feeling of sluggishness and fatigue among other symptoms. Raj also notes that "due to the lack of good bacteria, your body is more prone to bloating and bowel irregularity" as well.

Always Take Probiotics While on Antibiotics

"Antibiotics can affect natural organisms in the gut as well, causing some people to have fungal or yeast infections," explains Calapai. "Here is where probiotics come into play as a balancing agent to control normal intestinal flora. This is also why there is a common recommendation to take probiotics while you're taking oral antibiotics."

People have experienced some weight loss when taking a probiotic due to the improvement of their digestion and overall health.

"Probiotics are good for your bacteria and provide many health benefits when ingested," Raj agrees. "Probiotics have been linked to weight loss due to their ability to balance gut bacteria, improve better digestion, decrease inflammation, which is a result of less bloating, and help to better absorb nutrients from food. They have also been linked to faster metabolism and increased immunity. People have experienced some weight loss when taking a probiotic due to the improvement of their digestion and overall health."

Raj stresses the importance of taking a probiotic supplement during and after taking an antibiotic. "It can take several weeks to get your digestive health back on track," says Raj. "The Tula Daily Probiotic + Skin Health Complex [pictured above] is an excellent source of your daily probiotics. It's formulated with three probiotic strains including Lactobacillus rhamnosus GG...as well as two other strains and vitamin C, which supports metabolism, energy, and skin health. Taking this probiotic supplement on a daily basis will ensure you are feeding your body the good bacteria it needs to get back on track."

Both Calapai and Raj believe all people should consult their doctor before heeding any of this advice. "If antibiotics are medically necessary, then work with your doctor on ways to support digestive health during and after your course of treatment," explains Raj.

Calapai is on the same page: "Speak with your doctor to make sure you know how you're supposed to take your drug and if there are other ways you can ease your illness. If possible and only after consulting with your doctor, try alternative methods."

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