Gut Flora, Losing Weight, and the Real Reason Gastric Bypass Works

Filed Under: Digestive Health, Gut Bacteria & Probiotics, Weight Loss

With the beginning of each new summer, there always seems to be a renewed interest in losing weight or “shedding that winter coat.” For most people, their motivation seems to stem more from vanity rather than from improving overall health. Oddly, the desire to look better in a swimsuit or shorts is more motivating than trying to prevent an early demise from heart disease, diabetes, or cancer.

Regardless of the source of the motivation, losing weight has become a never-ending, lifelong struggle for the majority of people in this country. It shouldn’t be that way. But until they finally realize that maintaining a proper weight doesn’t depend on discovering some magic diet, but instead results from consistent eating and lifestyle habits, obesity will continue to be a growing epidemic.

Like many things in life, it can be the small, seemingly insignificant habits that gradually create and perpetuate the problem.

Microbes vs. Surgery

I’m constantly stressing the importance of gut microbes, the bacteria and other organisms that live in our intestinal tract. It’s something I’ve discussed and studied for decades, and finally, the scientific community is beginning to delve more heavily into that area. Now even more research has linked our bacterial flora to obesity. I’ve reported on similar studies but this latest one really caught my attention.

See a list of all articles about Gut Bacteria in the Gut Bacteria and Probiotics Index

I’m sure you’re well aware that bariatric surgery (gastric bypass surgery, banding, stapling, etc.) is touted as one of the most effective methods of treating obesity, as well as diabetes, hypertension, and heart disease. This latest research, however, suggests that a gastric bypass patient’s weight loss isn’t caused by the stomach not being able to hold as much food, but rather because the surgery changes the types of microbes in the gut. (Sci Transl Med 13;5(178):178ra41)

Following these surgeries, patients typically feel less hungry, they fill up more quickly, and they burn more calories while they are at rest. This can result in losing as much as 75 percent of their excess fat. It’s obvious that there’s a change in the metabolism of the patients, but the real question remains: What causes it?

The types of bacteria in the guts of obese individuals differ compared to those in thin individuals. These surgeries are known to change the types of microbes. But until now no one really knew whether the microbes in gastric bypass patients changed because they got thin, or if the patients became thin because the microbes changed.

In the study, after performing gastric bypass surgery on about a dozen obese test animals, researchers observed the characteristic loss of body fat, and it stayed off even when the animals were fed a diet that should have resulted in weight gain.

Researchers then took fecal samples from these animals and performed fecal transplants on another group of non-obese animals that were specially bred to not have any gut flora. Fecal transplants help reestablish a healthy population of microflora in guts that are lacking in these beneficial bugs. This second group of animals lost 5 percent of their weight in just two weeks, without any changes in their diet. This was considered a significant amount of weight loss because typically, these sterile-gut animals always gain weight when they are given any type of gut flora.

When researchers took a more in-depth look, they found that following gastric bypass surgery, there was a decrease in intestinal pH and an increase in bile acid concentration. (It also appeared that there might have been some hormonal changes as well.)

The correct pH is necessary for the digestion of protein, and bile acid is required to assimilate fat—and both are necessary for energy production. The primary reason we even consume food in the first place is to obtain energy. And when your body senses that the available energy is less than ideal, it tries to stabilize matters by storing fat.

Our bodies are always trying to reach a state of energy homeostasis, or balance. This occurs when the energy derived from food intake balances energy expenditure. But studies have shown that an excess of energy intake by less than 1 percent compared to daily energy expenditure leads to an increase in body weight and metabolic complications.

In simple terms, if you eat more calories than you burn, then you gain weight. And, the point that has been largely overlooked is that the less efficient your body is at converting food into energy, the more you have to consume to stay alive. When you overeat or eat incomplete foods, your body stores any excess as fat.

Make Your Body's Digestive Process More Efficient

If you want to lose excess fat and maintain proper weight, one of the keys is to make your body as efficient as possible when it comes to extracting energy from the foods you eat. There are a few steps you can take to make that happen.

First, consume nutrient-dense natural foods like nuts, seeds, beans, avocados, dairy products, eggs, and meat, which provide high nutritional value and energy, as well as satiety. Fried, fatty, processed, and packaged foods aren’t naturally balanced. They contain high levels of sugar, sodium, and preservatives. They aren’t energy efficient and leave your body craving more food to fill in the nutritional gaps. The end result is fat storage and weight gain.

Second, take digestive enzymes. Our digestive enzyme production declines as we age and, again, this decreases our ability to extract energy from food. This is why I have continually stressed the importance of digestive enzymes. If you’ve had your gallbladder removed, you’re even more disadvantaged than most when it comes to properly digesting fats, essential fatty acids, and fat-soluble vitamins. You need to be taking bile salts with each meal and continue on them for life. It’s not an overstatement to say they will prolong your life and help you avoid everything from heart disease to cancer.

Third, new research further illustrates how the bacteria in our bowel play a major role in making us even more energy efficient. We know that the bacteria in our gut extracts, or harvests, energy from dietary compounds like fiber, which we ingest but can’t digest. Human digestive enzymes can’t break the bonds of dietary fiber, but the bacteria in the bowel can. (Physiol Rev 01;81(3):1031–1064)

Gut bacteria ferment fiber into short-chain fatty acids like butyrate that protects against colon cancer. Other fatty acids protect against inflammatory bowel disease and the resulting increase in intestinal permeability. They also influence pancreatic enzymes, appetite, immune function, and carbohydrate metabolism, just to name a few other functions. (Physiological & Clinical Aspects of Short-Chain Fatty Acids;2004)

Bile Doesn’t Get the Respect It Deserves

One of the most interesting new findings occurred when researchers found that bile concentrations increased when they gave fecal transplants from thin animals to obese animals. Bile doesn’t get much attention in the medical world. It should.

Bile is made in the liver, and stored in and released by the gallbladder to help emulsify or break down dietary fat. (You could think of bile as a biological detergent.) It’s so important that about 95 percent of bile gets reabsorbed and returned to the liver for use again. Most of this takes place through the intestinal walls. Another way it gets back to the liver is when bacteria toward the end of the colon deconjugate it or break it down so it can be reabsorbed into the bloodstream. (Am J Clinical Nutr 69;22(3):284–291)

Only a few strains of gut bacteria are known to have the ability to metabolize bile acids, and the amount recovered this way has never seemed to be that important. But when you consider that the importance of bile has been largely overlooked, then it’s no surprise. Based on the research, I think it’s going to turn out to be extremely important. To me, it appears that increasing the reabsorption of your bile can have a major impact on both your weight and your overall health.

Bile acids also regulate sugar and fat metabolism, improve peripheral blood flow, and lower inflammatory markers in patients with chronic heart failure. (J Am Coll Cardiol 12;59(6):585–592)

And, partially contributable to the action of increasing bile concentrations, probiotics have been shown to lower cholesterol levels by as much as 22–32 percent. Bile in the colon also appears to protect beneficial strains of bacteria and improve their survival in the colon. (Appl Environ Microbiol 06;72(3):1729–1738) (Appl Environ Microbiol 89;55(7):1848–1851) (Microbial Ecol Health Dis 94;7:315–329)

Surgery-Free Steps to Long-Term Weight Loss

The first study I mentioned indicates that one of the primary reasons gastric bypass surgeries help someone lose weight is because they cause a change in the type of bacteria in the gut. This, in turn, makes the gastrointestinal tract more efficient at extracting energy from food, resulting in a reduction of appetite and food intake. This begs the question, “Can you actually lose weight and help keep it off simply by changing the bacterial flora in your gut?”

That actually appears to be the case. But don’t expect to take a single probiotic supplement and get the same effects as a gastric bypass. The human body is far too complex for that to occur.

Every year we learn more about the role of specific bacteria in the colon and exactly what they do. Specific probiotics in combination with fecal transplants could turn out to be a natural, noninvasive way to lose weight and actually cure a lot of the problems that are so common today.

I’ve detailed exactly how to perform fecal implants, and I think they are one of the most effective and underutilized techniques we have for dealing with many serious gastrointestinal issues such as inflammatory bowel disease. But to be a long-lasting and true cure, it can only be part of a larger change to our diet and lifestyles. For new bacteria to get established and flourish, the environment within the gut must be changed as well.

For the time being, there are some steps short of gastric bypass that you can take to help lose weight and keep it off.

  • Balance your energy intake with the energy you burn. If you’re using aerobic exercise exclusively to lose weight and body fat, you need to concentrate more on weight lifting and building muscle. Increasing muscle tissue is one of the fastest and easiest ways to burn more energy. Muscle tissue burns calories 24/7, even while you’re at rest.
  • Balance your thyroid using a natural iodine supplement like Iosol from TPCS Distributors (, 800-838-8727), and a natural thyroid glandular like Thytrophin PMG from Standard Process Laboratories (available by prescription but can also be purchased online). Hypothyroidism, which is directly responsible for slower metabolism, is one of the most common conditions in our society.
  • Consume nutrient-rich foods and avoid processed and nutrient-deficient, sugar-rich foods. And keep in mind, artificial sweeteners are just as bad as sugar. They fool your body into thinking blood sugar levels have increased and trigger many of the same detrimental reactions. They give the sensation of sweetness without the satiety, which leads to cravings and increased food consumption.
  • Minimize or avoid using prescription and over-the-counter drugs. They change the body’s internal environment and disrupt normal gut bacteria.
  • Don’t underestimate the potential benefits of digestive enzymes, fermented foods, and the regular use of a quality probiotic supplement combined with proper diet. The more efficient your body becomes at extracting the necessary nutrients from the food you eat, the less food you will consume. When research shows that you can obtain weight-loss effects typically only associated with gastric bypass by making your digestive system more efficient, that’s a very powerful concept.

Forty years ago, it was rare to see someone who was obese. In a single generation, obesity has gone from being a social and medical issue to a full-blown public health disaster. Today, 70 percent of adults in this country are either overweight or obese—and the problem is only getting worse.

Obviously the public is getting the wrong message about how to deal with obesity. That probably shouldn’t be any surprise when you consider the physical state of the messengers—our own doctors. Roughly 50 percent of doctors in this country are overweight and 11 percent are obese!

Dietitians and doctors are still condoning the use of diet sodas and low-fat diets, as well as unfermented soy products, soybean oil, and corn oil.

Research has shown that unfermented soy products mimic estrogen and disrupt hormone balance. The body converts these vegetable oils into endocannabinoids, compounds similar to those found in marijuana that stimulate appetite centers in the brain. And we’re still routinely giving antibiotics to our infants, despite research showing they disrupt the delicate balance in gut flora and cause excess weight gain by age 3. In this case, the inmates are running the asylum.

Read More About Gut Bacteria and Digestive Health

Gut Bacteria and Probiotics Article Index
See a full list of articles by Dr. Williams about gut flora, probiotics, and the microbiome. Read more
Gut Bacteria May Influence Food Cravings
Learn how gut bacteria manipulate which foods we crave, in order to get the foods they need to survive. Read more
Healthy Gut Bacteria Linked to Weight Loss
Read about a study in which the bacteria Lactobacillus gasseri contributed to weight loss. Read more
How to Choose the Best Probiotic Supplement
Learn the four criteria that Dr. Williams uses to decide whether a probiotic supplement is worth purchasing. Read more
Traditional Fermented Foods That Boost Digestive Health
Learn which traditional fermented foods have the most gut health benefits. Read more
9 Ways That Good Gut Bacteria Support Your Overall Health (That Have Nothing to Do With Digestion)
Learn about the wide-ranging health effects of gut bacteria, including their influence on immune health, mood, and weight management. Read more


DISCLAIMER: The content of is offered on an informational basis only, and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified health provider before making any adjustment to a medication or treatment you are currently using, and/or starting any new medication or treatment. All recommendations are "generally informational" and not specifically applicable to any individual's medical problems, concerns and/or needs.

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