Gut Health and Obesity

Written by: Kevin Cann

So many people are told to eat less and exercise more when weight loss is the ultimate goal. We often assume that the greatest problem we face is lack of physical activity and easy access to high calorie, low quality food. In some cases this definitely may be the problem. Put down the bag of chips and do some exercise and you may see some weight loss. This weight loss may or may not be permanent, and in some cases there may even be weight gain. Why is it that people eat less and exercise more, but can’t sustain weight loss? There are a number of issues that can cause this scenario.

One of the answers to that question is buried right in the place that is giving us so many problems; our gut. In our gut there are two main types of bacteria: bacteroidetes and firmicutes. Studies have shown in mice and in humans that the bacterial makeup of the intestines differs between obese and lean subjects. Animal studies and human studies have shown that obese people have lower bacteroidetes and higher levels of firmicutes, but there is some contradictory data out there on gut bacteria composition (Harris, 2011). The bacterial makeup of the gut in obese individuals has been shown to actually increase the amount of energy extracted from food. This has been shown in experiments with mice where the gut flora of obese mice was switched with lean mice. The obese mice lost weight and the lean mice gained weight. Studies such as these show that obesity is a pathophysiological disease (Turnbaugh, 2006).

This change in gut flora can be the cause of us overeating. Andrew Gewirtz showed that insulin resistance and increased appetite can be transferred from mouse to mouse in an experiment that he ran. He even goes on to state in that study that he believes overeating is not just a matter of not having will power, but the gut bacterial makeup is what is driving the appetite (Vijay-Kumar, 2010).

Obesity has also been linked to many disorders such as cardiovascular disease and cancer. The interesting part is that poor gut flora has also been linked to the same diseases. One cause is our body’s immune response to the bacterial endotoxin, lipopolysaccharide (LPS). Our body responds by initiating an inflammation response. The resulting inflammation can suppress our immune system and leave us open to illness. Also, low grade inflammation from LPS has been linked to insulin resistance in studies (Wellen, 2004). The other factor is our gut bacteria have evolved with us.

One way bacteria have evolved is in their ability to extract energy from indigestible fiber. Jumpertz did a study comparing stool energy to energy consumed while feeding subjects meals that varied in caloric content and observing changes in gut microbiota. He concluded that with a 20% decrease of bacteroidetes and a 20% increase of firmicutes there was an increase in energy harvest of around 150 calories (Jumpertz, 2011). That study shows one way for counting calories to be ineffective, how can one person know what their energy expenditure truly is?

Our gut bacteria are not only 84% of our immune system, but they also have the ability to drive our appetite for high calorie foods, increase the amount of systemic inflammation we face, and also extract more calories from the foods we are eating. A primary goal of any weight loss program should be to focus on foods that heal the gut. Typically “bad” bacteria like to feed off of sugar and refined carbohydrates, while our “good” bacteria feed off of fruits and vegetables. This makes sticking with a paleo diet for 30 days even more important. That way the good bacteria can overtake the bad bacteria and allow our gut to heal.


K. E. Wellen and G. S. Hotamisligil (2005), Inflammation, stress, and diabetes. The Journal of Clinical Investigation, vol. 115, no. 5, pp. 1111–1119, 2005.
R. Jumpertz, D. S. Le, P. J. Turnbaugh et al. (2011). Energy-balance studies reveal associations between gut microbes, caloric load, and nutrient absorption in humans. American Journal of Clinical Nutrition, vol. 94, no. 1, pp. 58–65, 2011.
M. Vijay-Kumar et al. Altered Gut Microbiota in Toll-Like Receptor-5 (TLR5) Deficient Mice Results in Metabolic Syndrome. Retrieved on May 7, 2012.
Turnbaugh, Peter (2004). An obesity associated gut microbiome with increased capacity for energy harvest.
Harris, Kristina (2012). Is the gut microbiota a new factor contributing to obesity and its metabolic disorders? Journal of Obesity. Retrieved on May 1, 2012.


Kevin is owner of Genetic Potential Nutrition. He is a holistic nutritionist, wellness coach, and strength coach. He works with people fighting illness, to competitive athletes. Check out his site at

Categories: General, Weight Loss


Robb Wolf’s 30 Day Paleo Transformation

Have you heard about the Paleo diet and were curious about how to get started? Or maybe you’ve been trying Paleo for a while but have questions or aren’t sure what the right exercise program is for you? Or maybe you just want a 30-day meal plan and shopping list to make things easier? Then Robb Wolf’s 30 Day Paleo Transformation is for you.


  1. Anna says

    So, can we infer that good bacteria are comprised of bacteroidetes and bad bacteria are comprised of firmicutes? And eating sugar and refined carbohydrates will stimulate growth of the later but eating fruits and vegetables will stimulate growth of the former?
    If this is the case, is there another way to increase bacteroidetes among our gut flora? For instance, is there a particular fermented food that favors one over the other? Many thanks.

  2. says

    It really is seen as an insulin shots resistance or perhaps insufficient blood insulin generation. The particular symptoms occurs when the try out cells in the islet involving langerhans discharge insulin shots to the system

  3. says

    Gut microbiota is CRUCIAL to the maintenance of healthful body fat mass level. Obesity is hellishly complicated. The unknowns are far greater than the knowns. Dr. Jeffrey Friedman has noted 15 % of morbid obesity is due to mutations in one or more of these four genes: NPY-R’s, NPY-LEPRb, MC4, aMSH-LEPRb

    More research needs to be done on why the body induces an extremely strong chemo-mechanical efficiency in the muscles of most weight reduced obese people. The bnody never adjusts to a chronically weight reduced state. This effect persists the rest of your life. The Blogosphere addresses none of this. I am in personal contact with many top obesity researchers.

  4. LeakyGutGal says

    Interesting. I never looked at it from the perspective that bacteria drives my appetite and cravings. This explains why it is important to include a probiotic in any leaky gut cure program.

    The more good bacteria, the less I will crave sugars. Thanks so much. I have been on a leaky gut cure but let the probiotics go due to cost. But since I am stalled on losing weight and my cravings still haunt me, time to add back some good bacteria and personally test out this info.

    Thanks, great info to have!

Join the Discussion