They are found in both supplements andfermented foods.
Probiotics may improve digestive health, heart health and immune function, to name a few (2,3, 4, 5).
Several studies also suggest that probiotics can help you lose weight and belly fat.
Gut Bacteria May Affect Body Weight Regulation
There are hundreds of different microorganisms in your digestive system.
The majority of these are bacteria, most of which are friendly. Friendly bacteria produce several important nutrients, including vitamin K and certain B-vitamins.
They also help break down fiber that the body can’t digest, turning it into beneficial short-chain fatty acids like butyrate (6).
There are two main families of good bacteria in the gut: bacteroidetes and firmicutes. Body weight seems be related to the balance of these two families of bacteria (7, 8).
Both human and animal studies have found that normal-weight people have different gut bacteria than overweight or obese people (9, 10, 11).
In those studies, people with obesity had more firmicutes and fewer bacteroidetes, compared to normal-weight people.
There are also some animal studies showing that when the gut bacteria from obese mice are transplanted into guts of lean mice, the lean mice get fat (11).
All of these studies suggest that gut bacteria may play a powerful role in weight regulation.
Bottom Line: There are many different microorganisms in the gut, mostly bacteria. Several lines of evidence suggest that these gut bacteria can have powerful effects on body weight.
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