by Craig Weatherby

The October 22 issue of The New Yorker magazine featured a startling article on research into the friendly bacteria known as “probiotics”.

In his article – titled “Germs Are Us: Bacteria make us sick. Do they also keep us alive?” – Michael Specter reported on some truly astonishing findings.

For example, Barry J. Marshall and J. Robin Warren earned a Nobel Prize in medicine for discovering that a bacterium called Helicobacter pylori is the leading cause of ulcers.

But there's now good evidence that body levels of the hormones that send hunger or satiety signals to the brain (i.e., ghrelin and leptin) become disordered in people who lack H. pylori.

Thanks to heavy use of antibiotics, an increasing number people have grown up without H. pylori bacteria. Consequently, these folks tend to overeat and become overweight or obese.

And in 2006, researchers from Washington University in St. Louis found that microbial populations (microflora) in the gut differ between obese and lean people … and that when obese people lose weight their microflora reverts back to that observed in lean people.

Last year, the same team reported that probiotic bacteria produced a change in many metabolic pathways in mice … particularly those related to carbohydrate (sugar/starch) metabolism.

Friendly bugs and weight: Species matters
Most recently, a review of the clinical and animal evidence affirms the idea that – when it comes to weight control – probiotic bugs are not created equal (Million M et al. 2012).

The authors of that review found that Lactobacillus acidophilus – the bacterial strain commonly used to ferment yogurt, and put in probiotic supplements – resulted in significant weight gain in humans and in animals.

In contrast, ingestion of Lactobacillus plantarum was associated with weight loss in animals and Lactobacillus gasseri was associated with weight loss both in obese humans and in animals.

As they concluded, “Different Lactobacillus species are associated different effects on weight change that are host-specific. Further studies are needed to clarify the role of Lactobacillus species in the human energy harvest and weight regulation. Attention should be drawn to the potential effects of commonly marketed lactobacillus-containing probiotics on weight gain.” (Million M et al. 2012)

Now, the results of a clinical trial seem to identify two probiotic bugs that help keep body fat in check.

Probiotics may help cut body fat levels
The results of the new clinical trial, performed at the University of Winnipeg, Manitoba indicate that two probiotics help to reduce body fat … and suppress a dangerous pathogenic bug (Omar JM et al. 2012).

The randomized, double-blind crossover trial was conducted by scientists from the University of Manitoba, McGill University, and Micropharma Limited.

The researchers fed 28 healthy but overweight people one of three kinds of meals for 43 days, and their diets contained just enough calories to maintain their current body weights.
  • Control Meal containing no probiotics.
  • Test Meal containing FAE-active Lactobacillus fermentum
  • Test Meal containing BSH-active Lactobacillus amylovorus
Participants ate their assigned meal regimen over six weeks, followed by a “wash-out” period to clear the subjects' systems before proceeding to the next treatment.

The participants consumed the probiotics in yogurt and were not allowed to eat any other food other than the meals provided them.

Each participant's fecal matter was tested to measure their gut flora before and after each treatment, and body fat was measured using a special x-ray scanner.

The results showed that the probiotic meal regimens lowered body fat by three to four percent over six weeks.

Co-author Dr. Peter Jones commented on the seemingly small change: “Four percent over six weeks doesn't sound like a deal maker but just do the math. Take it out for a year or a decade and you're talking about ... a pretty sizable change”.

Why would probiotic bacteria affect deposition of body fat? As Dr Jones said, “If you change the types of bugs in your gut, those bugs actually metabolize energy which would otherwise be absorbed and laid down as new fat”.

In their published paper, the authors expressed this hypothesis in scientific terms (Omar JM et al. 2012):
  • “Consumption of Lactobacillus amylovorus or Lactobacillus fermentum bacteria as probiotics may assist in reducing the development of obesity, since these bacteria may confer modifications to energy handling within the host.”
  • “This creates a microbiome which favors fat oxidation over fat storage, by populating the gut with protective bacteria and preventing the proliferation of pathogenic bacteria, which may ultimately lead to a reduction in body adiposity and transformation of body composition.”
Also, the group taking BSH-active Lactobacillus amylovorus showed a significant cut in their levels of clostridial cluster IV … an unhealthy bacteria related to C. difficile, a bug that often makes hospital patients very sick.

Clearly, more research is needed to pinpoint the bacteria that help with weight control and those that hurt.

It may be that bacteria have much more to do with weight control than ever thought ... and possibly much more than the factors usually cited, such as corn syrup.

  • McNulty NP, Yatsunenko T, Hsiao A, Faith JJ, Muegge BD, Goodman AL, Henrissat B, Oozeer R, Cools-Portier S, Gobert G, Chervaux C, Knights D, Lozupone CA, Knight R, Duncan AE, Bain JR, Muehlbauer MJ, Newgard CB, Heath AC, Gordon JI. The impact of a consortium of fermented milk strains on the gut microbiome of gnotobiotic mice and monozygotic twins. Sci Transl Med. 2011 Oct 26;3(106):106ra106. doi: 10.1126/scitranslmed.3002701.
  • Million M, Angelakis E, Paul M, Armougom F, Leibovici L, Raoult D. Comparative meta-analysis of the effect of Lactobacillus species on weight gain in humans and animals. Microb Pathog. 2012 Aug;53(2):100-8. Epub 2012 May 24.
  • Omar JM, Chan YM, Jones ML, Prakash S, Jones PJH. Lactobacillus fermentum and Lactobacillus amylovorus as probiotics alter body adiposity and gut microflora in healthy persons. Journal of Functional Foods. Published online ahead of print, doi: 10.1016/j.jff.2012.09.001
  • Sonnenburg JL, Chen CT, Gordon JI. Genomic and metabolic studies of the impact of probiotics on a model gut symbiont and host. PLoS Biol. 2006 Nov;4(12):e413.