You know that what you put in your mouth affects the number on the bathroom scales, but did you know that the health of your gut could influence your waistline too? A growing body of research suggests that the microbiota in your stomach could affect your weight.
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A recent study published in the journal Cell found that people who are slim have a greater abundance of one type of bacteria called Christensenellaceae, whereas those who are obese have less of the bacterial.
Another study from Washington University School of Medicine found that obese people have 70 percent fewer and less diverse microbes in their stomach compared to people who are slim. While the type of bacteria you have is partly down to genetics, the good news is that it may be possible to change the types and amount of bacteria in your gut.
Rob Knight, Ph.D., a cofounder of the American Gut Project says that the correlation is so strong, "we could predict whether one was lean or obese based solely on their gut microbes".
How does gut bacteria affect weight?
There are trillions of bacteria in your gut - and 500 different species - which together act as a huge chemical factory to help digest food, produce vitamins, regulate hormones and excrete toxins. Like a rainforest, the microbes in your stomach are a diverse and interdependent ecosystem - and they need to be in balance in order to work efficiently. If you have too many bad bacteria, like parasites or yeast, or not enough good bacterial (like Lactobacillus or Bifidobacteria), the result can be poor health.
Experts aren't sure exactly how gut bacteria influences weight, but many believe that gut microbiota affect how many calories and nutrients are taken from food and absorbed by the body. It's also been suggested that some intestinal microbes may change your sensitivity to insulin, encouraging the body to burn fat rather than store it.
In addition, some studies have found a link between the stomach's production of the hunger hormone ghrelin and helicobacter pylori, a microbe known to cause ulcers and stomach cancer. While antibiotic treatments have reduced H. pylori infection rates, it could be bad news for you waistline. When you eat, your level of ghrelin goes down, but if you don't have enough Helicobacter in your gut, it remains high – and as a result you still feel hungry.
Some experts believe that the wide use of antibiotics – prescribed to humans or used in the food industry (given to livestock to keep them healthy and gain weight) could be partly responsible for the rise in obesity in modern times. Consuming these antibiotics, it's suggested, may upset the balance of microbes in the stomach, leading to weight gain.
What you can do
Genetics plays a part, but the foods you eat can have a significant effect on your gut health.
Up your intake of fibre
Eating more fibre is one of the best things you can so to support healthy gut flora. Increase your intake by eating more vegetables, fruits and whole grains. Some foods, such as garlic and leeks, are packed with prebiotics – so make sure to include these in your diet.
Cut down on sugar
Eating too much sugar can starve gut flora. Microbes either die or survive by feeding on the mucus inside your intestine, which some experts believe could contribute to low-level inflammation, which has been linked to weight gain.
Instead of reaching for the biscuit tin, snack on fruit or a handful of nuts, and cut down on processed foods that are high in sugar, such as jars of pasta sauce and tinned soups. Switching to brown rice and whole-grain pasta instead of white is also a good idea.
Eat Greek yoghurt
Regularly eating fermented foods such as yogurt will help to increase the probiotics in your gut. Research published in the New England Journal of Medicine found that people who regularly eat yoghurt are more likely to be of a healthy weight.
Choose good fats
Some studies suggest that high-fat diets can adversely affect your gut flora and lead to inflammation and weight gain. Experts now advise ditching vegetable oil and using coconut oil or extra-virgin olive oil and to eat avocadoes, almonds, and fish rich in omega-3s.
Take a supplement
If you're not regularly eating fatty fish, consider taking an essential fatty acids supplement. Taking a probiotic supplement can also help to reduce gut inflammation while cultivating health and the growth of good bacteria.