Gut Microbes Linked to Obesity Cause and Treatment

22/12/06 US scientists have discovered that "gut microbes" - bacteria that live in our digestive tract - could be powerful clues to the cause and treatment of obesity.

This remarkable news was published in Nature this week and conducted at Washington University School of Medicine in St. Louis.

The clue lies in the relative abundance of two major families of intestinal bacteria: Firmicutes and Bacteroidetes. These make up 90 per cent of the bacteria in the gut of humans, and, coincidentally, white mice.

Researchers in the first of two parallel studies found that as obese people lose weight, the balance between the Firmicutes and the Bacteroidetes changes - the latter increasing in abundance as an overweight person gets slimmer. (It would seem that the microbes ending in "cute" are perhaps not as lovable as their name implies!).

The second study was conducted in a neighbouring lab using white mice. Here, researchers discovered that the bacteria in the guts of obese white mice were more efficient at extracting calories from complex carbohydrates than the bacteria in the guts of slimmer mice.

Also, in an earlier study, they had shown that the guts of obese mice had the same depletion of Bacteroidetes as found in the guts of the obese humans.

This means that you could have two guys eating the same amount of food (i.e. consuming the same calories) each day, and doing the same amount of exercise (i.e. burning equal number of calories) but over the course of several years, one gradually gets fatter and the other stays the same. Why? Because the one who stays the same has more Bacteroidetes in his gut, extracting fewer calories from the same amount of food.

The poor guy who gets fatter has a more efficient calorie grabber in his gut, and the excess gets stored as fat - putting him at higher risk of eventually becoming obese.

Trillions of "friendly" gut bacteria digest the food we eat by breaking down complex molecules like polysaccharides (complex carbs found in fruit, vegetables and grains) into simple sugars for energy. The excess is converted to fat for longer term storage. However, these studies suggest that the simple equation (calorie value of food intake) - (energy we use) equals (the fat we store), is different for different people.

These studies form part of a growing body of research revealing fascinating new insights into what we are made of and what makes us tick.

We used to think that the human body was a collection of cells with the same DNA imprint - like a unique bar code for each person. However, within us, in our guts, lie communities of microbes that outnumber our cells by 10 to 1, and, according to the researchers behind these two studies, "they may contain 100 times more genes than our own human genome".

The researchers suggest that intestinal bacteria could become "biomarkers, mediators and potential therapeutic targets" in the fight against obesity.