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The Secret World Inside You - Obesity (2)

Gaining Weight? Why Gut Microbes May be to Blame

Do you long for foods that aren't good for you? Is your metabolism sluggish? Do you retain body fat and gain weight easily?

If you answered yes to any of these questions, you may want to take stock of your gut microbiome – the collection of microbes that live in your digestive tract. These microorganisms not only play a role in your digestion and immunity but your mood, energy, cravings, appetite and weight.

Science initiatives like the Human Microbiome Project and the American Gut Project have helped us to better understand and appreciate just how important these microflora are to our health and well-being. And, science is making it clear that gut flora plays an important role in weight gain.

Now, much of this research is being showcased at the American Museum of Natural History in NYC in an exhibit called The Secret World Inside You. The exhibit covers many topics ranging from how we acquire our set of microbes at birth to how our microbial world within us changes with age, diet and medications like antibiotics.

I recently visited the microbiome exhibit and was fascinated by the section devoted to diet and obesity. I found it fascinating especially as much of this science was incorporated into the development of LeanBiotics™, a weight management product line based on altering your gut microbiome through food and supplements to resemble that of lean people. Here’s a peek at what I saw:


Is there a link between probiotics and weight loss? Could probiotic bacteria help you lose weight? Amazingly, research showed exactly that - at least in mice. But there’s reason to think it could work in humans too.

Appetite Control

Can disrupting your microbiome make you hungry? Researchers found that removing a bacterium called Heliobacter pylori from people’s stomachs could make them hungrier – and eventually heavier. Many other bacteria may have similar effects.

How does it Work?

When H. pylori goes down, ghrelin and appetite goes up. When your stomach is empty, it releases a hormone called ghrelin that makes you hungry. After you eat, ghrelin levels go back down. But if stomach bacteria called Heliobacter pylori are removed, ghrelin keeps pumping out at six times normal levels – and people keep eating.

Weight Loss Bacteria?

Obese people – and obese mice – both have dramatically reduced levels of the bacteria Akkermansia muciniphila. Obese mice have 100 times less than thin mice. Restoring these bacteria made obese mice lose weight. It also restored their intestines’ protective mucus layer , reducing inflammation and diabetes risk.

The Secret World Inside You - Weight Loss Bacteria

Already in Us?

Since we already have some Akkermansia muciniphila, boosting their numbers does not require taking live bacteria – you can just stimulate the growth of the ones you already have. Supplements of oligofructose – a carbohydrate found in onions and bananas – increased A. muciniphila levels just as much as live supplements – while also reducing appetite. (I was particularly interested in this finding, because when I got my gut microbiome tested from Genova Labs last year, my results showed that my A. muciniphila levels were way off the charts!).


Is the microbiome a cause of obesity, or an effect? The answer is…probably both.

Dr. David Rahm Explains How LeanBiotics Rebalances Your Gut Microbiome

There is no universal “fat microbiome” or “thin microbiome”. Everyone is different. Yet in some populations, leaner people tend to have very different microbiomes than their heavier neighbors. So microbes seem to be a factor in body weight, along with diet and exercise.


In one study, one group of mice was given microbes from obese people. The others got microbes from lean people. The mice with the obese people’s microbes gained more weight – from the same food! Their microbes apparently helped store more calories as fat.

Weight Loss

One way to lose weight is with gastric bypass surgery, which reduces the size of the stomach and intestines – and radically alters the microbiome. Success in dieting has also been linked to the microbiome. Could changing your microbiome help you lose weight? More research is needed to answer the question.

…or effect?

Your microbial populations shift in response to the food they receive. A high-fat, high calorie diet causes some bacteria to multiply, whereas a high-fiber, plant based diet nourishes a different group. So the difference between obese and lean people’s microbiomes partly just reflects their food choices.


The livestock industry spends millions of dollars adding antibiotics to animal feed. Why? The drugs make animals gain more weight from the same food. It works for cows, chickens, pigs – and probably people.

Phasing Out

In 2011, 30 million pounds of antibiotics were given to U.S. farm animals – a practice banned in Europe because it breeds antibiotic resistance. The United States is currently phasing in voluntary restrictions.

Over 70 percent of the antibiotics used in the U.S. are fed to livestock to make them gain weight, not to cure disease.

Of Mice and Medicine

When taking antibiotics to cure disease, people take them in high doses for a short period of time – not constant, low doses, like those used to fatten animals. Is the effect on weight the same? Unfortunately, mouse studies showed that these doses also make animals gain weight


States where people take the most antibiotics also have more obese people. Could antibiotics be making people fatter? Antibiotics have been proven to make farm animals gain weight, and there’s evidence they fatten people, too. But these maps alone are not proof. Obesity correlates with other factors, too – including income – making it hard to pin down a single cause.

The Secret World Inside You - Antibiotics & Obesity

Antibiotic Use, by State

Compare these maps. States that use more antibiotics tend ot have more obesity. But why? Do antibiotics cause obesity? Or do obese people just get sick more? The maps don’t say. Correlation doesn’t prove causation. In this case, lab studies provide further evidence antibiotics can cause obesity- but they are just one factor on a long list that includes diet and exercise.


The food you eat doesn’t feed just you – it also feeds your microbiome. Different foods are processed in different parts of your digestive system, and nurture different bacteria. The majority of the helpful ones live in your large intestine. Think of these bacteria as pets to feed and care for – yet another reason to eat more vegetables and less junk food!


A probiotic is anything that contains live organisms that are good for you. They can be swallowed in pills, or consumed in natural, fermented foods like yogurt, sauerkraut and kimchi. Several probiotics have been shown to benefit your digestive system and immune system.

The Secret World Inside You - What's a Probiotic

Who take Probiotics?

Antibiotics kill beneficial bacteria as well as pathogens, so probiotics are often prescribed alongside them. By temporarily replacing the missing microbes, probiotics can prevent opportunistic infections that cause diarrhea or yeast infection.

What’s a Prebiotic?

Instead of swallowing live bacteria, why not swallow food for the ones you already have? Prebiotics are like fertilizer for desirable bacteria, helping them grow and multiply.

Research into the human microbiome will continue given that the Obama administration just announced that it is committing $121 million to a two-year effort to a federal microbiome project. The Bill and Melinda Gates Foundation will commit $100 million in new grants over the next four years. And, the University of Pittsburgh will create a Center for Medicine and the Microbiome. Stay tuned!

The Secret World Inside You - Build a Diverse Microbiome

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