How Your Gut Bacteria Can Influence Your Weight

There are likely more bacterial cells in your body than human cells. Your body contains trillions of bacteria. It is estimated that in a 154-pound (70-kg) man, there are around 40 trillion bacterial cells and only 30 trillion human cells (3).

Most of these bacteria live in a part of your large intestine called the cecum. There are hundreds of different types of bacteria in your intestines. While some may cause disease, most of them carry out essential tasks to keep you healthy (4).

For example, your gut bacteria produce certain vitamins, including vitamin K, and communicate with your immune system to help your body fight off infection (5, 6). Your gut bacteria can affect how different foods are digested and produce chemicals that help make you feel full. As a result, they can affect your weight.

A number of studies have shown that people with high fiber intake have a lower weight, which may be due to the role that gut bacteria play in digesting fiber (13, 14, 15).

A recent study found that the ratio of two types of bacteria in your intestines may determine how much weight you lose when given a particular diet. These two bacteria are Prevotella, which digests fiber and carbohydrates, and Bacteroidetes, which people who eat more animal protein and fat have more of (16). In this study, 62 people were given a high-fiber, whole grain diet for 26 weeks. Those who had more Prevotella in their intestines lost 5.1 pounds (2.3 kg) more body fat than those with more Bacteroidetes in their intestines (17).

A diet containing too much fat, sugar or calories can lead to elevated inflammatory chemicals in the bloodstream and fat tissue, which may contribute to weight gain (20, 21). Your gut bacteria play an important role in inflammation. A study in 292 people found that those who were overweight had lower gut bacteria diversity and higher levels of C-reactive protein, an inflammatory marker in the blood (23). However, some species of intestinal bacteria may reduce inflammation and prevent weight gain.

The Best and Worst Foods for Your Gut Bacteria

Whole grains, fruits, vegetables and fermented foods all support healthy gut bacteria, while too many sugary foods, artificial sweeteners and unhealthy fats can be bad for your gut bacteria.

(Source: Adapted from: https://www.healthline.com/nutrition/gut-bacteria-and-weight)