Your body is full of bacteria — but not all of them are bad. Probiotics are friendly bacteria that can be found naturally in fermented foods like yogurt or taken in supplement form. Many people take probiotics to help replenish their guts with good bacteria, especially after taking antibiotics.
Probiotics are necessary for your body to break down food and support a healthy immune system. They may also promote weight loss.
How Your Gut Bacteria Affect Weight Loss
Your gut contains many different bacteria, which are part of your microbiome, a collection of over 100 trillion microbes.
These bacteria all work together to help your body do the following:
- Break down nutrients
- Break down medications
- Protect against disease-causing germs
- Keep your gut lining healthy
- Influence your immune system
Dysbiosis happens when the bacteria in your gut become unbalanced. This can cause digestive problems like irritable bowel syndrome and inflammatory bowel disease, along with allergies and even brain disorders.
But the way bacteria affect your weight is still not fully understood. One study done on sets of twins found that those who were obese had less diversity of gut bacteria compared to those who were lean.
Other studies have discovered that certain bacteria strains may slow down weight gain. Some strains can reduce waist size, while others may help with weight loss. However, some researchers have not been able to find any connection between bacteria and weight.
Most scientists do agree that bacteria affect your metabolism. They do so by helping your body:
- Make vitamin K
- Make folate (vitamin B9)
- Make biotin (vitamin B7)
- Make vitamin B12
- Absorb magnesium
- Absorb calcium
- Absorb iron
- Break down carbohydrates
- Ferment fibers
- Make short-chain fatty acids
According to studies done on animals, these short-chain fatty acids can help your body tolerate sugar and use energy more efficiently. They may also help you feel full and suppress your appetite. More research needs to be done to see if these results translate in humans as well.
Do Probiotics Help With Weight Loss?
While good bacteria help you break down nutrients and get energy from your food, there isn’t clear evidence that taking a probiotic supplement or food containing probiotics can help you lose weight. Here's what some studies have found:
Visceral fat wraps around your organs and can affect how your hormones work. It's associated with obesity and leads to insulin resistance and type 2 diabetes. One clinical trial showed that people who have large amounts of visceral fat were able to lose some of this fat after drinking 200 grams of probiotic-containing fermented milk daily for 3 months.
But other trials using specific probiotic supplements show conflicting results. Some probiotic strains were linked to weight loss, while others were not.
Overall, the best probiotics for weight loss may depend on a variety of factors, including:
- How long you take them
- Probiotic type
- Your age
- Your starting weight
Risks of Probiotics for Weight Loss
While probiotics are generally safe, there can be some risks associated with taking them.
Quality. As a food product or supplement, probiotics don’t go through the same rigorous testing as medicines, which means you can’t be sure of the quality of the product you’re buying.
Because there are fewer regulations with probiotics, it's hard to tell exactly what you're getting and if the product even has enough bacteria to have any impact on your body. There have also been reports of products that have different strains than what are listed on the label.
Bacteria are also living organisms. If the product isn’t made or stored correctly, or is close to its expiration date, the bacteria might not survive long enough to have any beneficial effect on your gut.
Different strains. Probiotic supplements often have different bacteria strains. As mentioned earlier, researchers are still unclear as to which strains may have the most effect on weight loss. This is important to keep in mind if you're taking a probiotic specifically to help you lose weight.
Immune system problems. People who have compromised immune systems or severe diseases can get sick from taking probiotics. You should avoid consuming probiotics if you’re taking medications that suppress your immune system. It's best to talk to your doctor first before taking any probiotic supplement.
In general, while probiotics can have a positive impact on your metabolism, it’s still unclear how or if they can help you lose weight. If you’re concerned with your weight, consult your doctor about diet and lifestyle changes that can help you drop the pounds.
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National Health Service (NHS): “Probiotics.”
National Institutes of Health Office of Dietary Supplements: “Probiotics – Health Professional Fact Sheet.”
Nature: “A core gut microbiome in obese and lean twins.”
Nutrients: “Is It Time to Use Probiotics to Prevent or Treat Obesity?,” “Probiotics: How Effective Are They in the Fight against Obesity?”
University of Washington Center for Ecogenetics & Environmental Health: "Fast Facts About The Human Microbiome."