One of the most significant studies into how your microbiome (that is, the different bacteria, yeast, viruses, parasites & protozoa which live on & inside of you) can affect your weight was published in the journal Science in 2013.

The study took two groups of ‘germ-free’ mice (born via c-section so as to be effectively sterile) & inoculated them with two types of bacteria. One type was ‘obese’ bacteria & the other was ‘lean’ bacteria. These different bacterial groups were actually harvested from human being twins under the criteria that one of the twins had to be obese whilst the other had to be lean. They took the poo from the obese twin, harvested the bacteria from it & labelled it ‘obese’ bacteria, & they did the same for the lean twin & labelled it ‘lean’ bacteria.

Then they took these different harvests & inoculated the two groups of mice; one with the lean bacteria & one with the obese bacteria. All the mice were fed a commercial, sterilized mouse chow that was low in fat (4% by weight) and high in plant polysaccharides, yet there were significantly different outcomes for each group.

Incredibly, the mice inoculated with the ‘obese’ bacteria gained significantly more weight than those mice inoculated with the ‘lean’ community of bacteria; this was reproducible across experiments. 

The study has since become a standpoint for the microbiome-obesity argument, & throws into perspective the need for those with weight challenges to focus on the healthy alteration of their microbiome. It also gives light to the fact that calorie-restricted diets may not be the sole answer for those trying to lose weight.

Interestingly, another step conducted in the study was to then house both groups of mice together; an obese mouse with a lean mouse & what was found was that through the focal-oral microbial transfer pathway (yo – this translated to eating each other’s poo), the obese mice began to lose weight.

This means that there was a suppressive effect from the good ‘lean’ bacteria on the bad ‘obese’ bacteria, showing the potential for probiotic supplementation/intervention to have a significant impact on weight management. Probiotics are known to have a suppressive effect on pathogenic bacteria by starving them of food, physically crowding them out of your GI tract & also creating an inner environment that is more conducive to a healthy microbiome.

This study may be a significant turning point in our already changing attitudes to the obesity crisis currently challenging most western nations. In Australia 2 in 3 adults are overweight or obese, with 1 in 4 children the same.





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