Weight Gain – Weight loss – Gut Bacteria

Obesity can cause major health issues such as diabetes and cardiovascular disease.

Weight Gain Overweight

Now, the question is how much do lifestyle, diet and the microbiome (gut bacteria) play a role in this?

Scientists have found that gut bacteria play a key role in digestion and fat absorption, even in the amount of calories one absorbs from food. That is why some people can eat whatever they want and how much they want and never really gain weight while others eat a restricted diet and still gain weight.

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Two groups of gut bacteria

Bacteroidetes and

have been studied in mice in regard to obesity.

Scientists took two groups of sterile mice, meaning they killed all bacteria in the mice’s gut prior to the experiment, and reintroduced firmicutes and bacteroidetes in different ratios.

The mice with a greater amount of firmicutes gained weight and actually ended up being obese in comparison to the other mice with less firmicutes, while both groups ate the same food.

What happens is that firmicutes are able to extract more calories from food in the form of fatty acids.

Also, the kind of food you eat will cause a shift in the microbiota. Eating meals high in bad fats, such as vegetable oils, and high calories, leads to the die off of gram negative bacteria and specifically a die off of bacteroidetes.

Bacteroidetes are the kind you want more of in the gut in comparison to the firmicutes if you want to stay lean.

A high fat and a high caloric diet causes the die off of gram-negative bacteria.   When they die, they release Lipopolysaccharides (LPS) from the outer layer of the cell.

The German physician and bacteriologist Richard Pfeiffer (1858 – 1945) discovered those LPS’s and coined the term “endotoxin”.

Endotoxins are kept in the bacterial cell and only released when the cell wall is destroyed.

Now, those endotoxins cause gut inflammation and the loosening of the tight junction which hold the cells of the gut lining together. Leaky gut causes long term inflammatory responses which changes the microbiome and the person ends up with the formation of an obese gut flora.

The obese microbiome determines your cravings, how much you eat, and extracts more calories out of the food you eat.

Lifestyle change by itself is simply not enough to overcome weight gain and inflammation.

Exercise for example counts only about 20 % toward weight loss while

Diet counts about 80 %.

There Is HOPE

for someone who is overweight and has trouble losing weight.

Dietary changes toward a healthy diet with healthy fats, fiber rich foods, and less calories can change the microbiom within 24 hours.

Contact me if you would like to book a Free 20 minute Health Consultation


(1) Overweight and obese adults (self-reported), 2011, Statistics Canada, http://www.statcan.gc.ca/pub/82-625-x/2012001/article/11664-eng.htm (October 29, 2012)

(2) Ley, R.E., Turnbaugh, P.J., Klein, S., and Gordon, J.I. (2006). Microbial ecology: human gut microbes associated with obesity. Nature 444, 1022– 1023.

(3) Semova, I., Carten, J.D., Stombaugh, J., Mackey, L.C., Knight, R., Farber, S.A., and Rawls, J.F. (2012). Microbiota Regulate Intestinal Absorption and Metabolism of Fatty Acids in the Zebrafish. Cell Host Microbe 12, 277-288.

(4) Backhed, F., Ding, H., Wang, T., Hooper, L.V., Koh, G.Y., Nagy, A., Semenkovich, C.F., and Gordon, J.I. (2004). The gut microbiota as an environmental factor that regulates fat storage. Proc. Natl. Acad. Sci. USA 101, 15718–15723.