How Your Gut Bacteria Can Mess With Your Weight

How Your Gut Bacteria Can Mess With Your Weight Hero Image
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Microbiome is the term used to describe the vast ecology of bacteria (and viruses and fungi) that live on and in the body. Conventional medical wisdom may consider bacteria to be "bad" for us, representing the spread of disease, etc., but we have over 1,000 different types numbering in the trillions of "good bacteria" in and on our bodies and particularly in our gut.

These bacteria play many roles in our body, including:

  • Production of vitamins like B12, folate, niacin, and vitamin K
  • Caloric extraction and digestion
  • Maintenance of the gut wall and protection against bad bacteria
  • Regulation of the immune system and inflammation
  • Production of the short-chain fatty acid butyrate that fuels the brain and intestine
  • Weight loss and appetite regulation
  • Production of neurotransmitters such as dopamine and serotonin

That's quite a list! Lots of research has been done in the past two decades to explore how our microbiome can affect our health and our weight. Although the data in these studies is still developing, conditions such as type 2 diabetes, heart disease, inflammatory bowel disease, and obesity are being associated with changes in gut bacteria.

In terms of weight, Dr. Raphael Kellman, author of The Microbiome Diet, says, "Simply put, if you get the microbiome—that collection of bacteria inside you—healthy, you will lose weight."

"It's less about eating a certain percentage of carbohydrates, protein, and fat than about correcting the overgrowth of unhealthy bacteria, which is making you crave the wrong foods, triggering inflammation."

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The relationship between good bacteria and weight loss.

Here are a few reasons why improving your balance of good bacteria to bad bacteria may aid in weight loss:

1. Different bacteria in your gut extract different amounts of nutrients.

The textbook definition of how to lose weight is to eat fewer calories than you expend—the calories-in-vs.-calories-out theory. But the meaning of "calories in" is not exactly just counting the calories that go into your mouth and stomach. The calories that count are those extracted by your digestive enzymes and the trillions of bacteria in your intestines.

Overweight people tend to have more firmicutes bacteria, which convert food to calories at a higher rate than bacteroidetes, another type of bacteria that slim people have more of, which convert less food to calories. If you lose weight, you increase bacteroidetes and decrease firmicutes.

2. Gut bacteria can affect the immune system and inflammation.

Inflammation can trigger increased appetite and insulin resistance, which then increases unhealthy food cravings. Gut bacteria send chemical messages to the brain that sway our appetite and mood.

A poor diet, comprised of lots of processed foods, refined carbs, and sugar can feed bad bacteria, which cause us to crave even more of those foods, whereas increasing healthy bacteria helps curb cravings by decreasing inflammation. In addition, exercise releases an anti-inflammatory substance that enhances immunity and decreases inflammation.

3. A healthy gut helps production of the feel-good neurotransmitters.

Dopamine and serotonin are two neurotransmitters that are produced in the gut and affect the brain. They can potentially decrease stress eating and contribute to better food choices and overall sense of well-being. Without them, there can be moodiness, depression, and anxiety. A healthy balance of bacteria in your gut aids in the production of dopamine and serotonin.

Signs your microbiome is unhealthy:

What contributes to an unhealthy microbiome?

  • Infections such as Lyme disease, mold, or autoimmune diseases
  • Hormonal imbalances
  • Poor diet of simple sugars, processed, and low-fiber foods
  • Overuse of antibiotics, NSAIDS, and acid-reducing meds
  • Toxins like PCBs, lead, mercury, and arsenic

Genetics, age, and lifestyle also affect your microbiome, and more new studies are emerging that shed more light on how our microbiome affects our health. So how can we use this information to be healthier or to lose weight?

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How to feed your good bacteria:

Add more of the following into your diet:

1. Prebiotics:

Prebiotics are plant fiber compounds that pass undigested through the upper part of the GI tract and help stimulate the growth of good bacteria by feeding them. Some sources are asparagus, chicory root, garlic, Jerusalem artichoke, jicama, and onions.

2. Probiotics:

Probiotics are a type of good bacteria, similar to the ones that reside in your gut. Good sources of probiotics include fermented foods like yogurt, kefir, sauerkraut, miso, and kimchee. For supplements, a multistrain probiotic is recommended—bifidobacterium for your colon and lactobacillus works in your small intestine.

3. Fiber:

Fiber helps promote growth of friendly bacteria. Aim for 25 to 35 grams a day. Fiber is found in vegetables, fruits, nuts, seeds, and whole grains. Make your plate one-half to three-quarters vegetables and plant-based foods. If you are not currently eating lots of fiber, increase slowly and drink adequate water. Soluble fiber (found in flaxseed, sweet potatoes, apricots, oranges, Brussels sprouts, legumes, and oatmeal) has been shown to be the most effective type of fiber for weight loss.

4. Plants:

Eat a variety of plant foods to stimulate a larger variety of types of bacteria.

5. Healthy fats:

Consume more omega-3 fats found in fatty fish and flaxseeds, monounsaturated fats such as olive and avocado oil, and medium-chain triglycerides (MCT) found in coconut oil. Use these in place of other vegetable oils.

Foods to cut back on:

To help get more of the good bacteria, cut out the foods that feed the bad bacteria.

1. Processed foods:

Refined carbs, processed, and low-fiber foods and sugars.

2. Animal protein:

A diet heavy in fat and protein (such as meat and cheese) feeds a type of bacteria, biophilia, that has been linked to inflammation.

3. Artificial sweeteners:

These may negatively affect the microbiome and cause increased fat synthesis and insulin resistance even though they contain no calories.

While weight loss relies on many factors, having balanced bacteria in your gut is a good starting place and will also improve your overall health and well-being. While many of us are born with a certain balance of types of bacteria, there is a lot you can do to influence that balance throughout your life, such as eating well, exercising, reducing stress, and getting enough sleep.


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