Bacteria - New Clues in the Fight Against Obesity

Obesity has long been a challenge for both physicians and their patients. It's also been confusing, as many people - including the obese - wondered why they had the problem when others with the same lifestyle did not.

Now, studies at the Washington University School of Medicine in St. Louis are providing more clues to the secrets of obesity - its causes, and possibly even treatment as well.

The first study, done early in 2006 with mice, showed that a particular bacteria, B. theta, when injected into the intestinal tract, caused the mice to process their food better. But when B. theta was combined with an archaeon (single-celled organism) called M. smithii the mice actually gained weight.

More recent research involved comparing bacteria in the feces of both obese and lean human subjects. At the beginning of the study it was noted that the proportions of two types of bacteria, Bacteriodetes and Firmicutes, were different in the obese people when compared to those of the lean subjects. Then, after a year of dieting, the formerly obese participants - who had now lost a lot of weight - had bacteria proportions that were much closer to those of the lean participants.

It's been known for a long time that the bacteria in the intestinal tract help with the digestion of food. But these studies seem to indicate that some bacteria are better at digestion than others. Bacteria like Firmicutes and the archaeon M. smithii seem better able to extract energy - in the form of calories - from food. The problem is that these calories are then stored in the body - as fat.

This is just beginning research, and it raises many questions, including the following:
- Can the quantities or proportions of different bacteria in the intestinal tract make us more or less prone to gain weight?
- Do these quantities and proportions indicate an increased risk of obesity, perhaps at a later stage in life?
- If these are true indicators of obesity, can they be changed - for example, with inoculations like those given the mice - to help someone lose weight or be less prone to gain it?

Like most early research, there are more questions than answers. But the questions will at least provide direction for further study.

Scientists do say that this research doesn't eliminate the role of other factors in the problem of obesity - things like overeating or lack of exercise. So people looking for an easy way to lose weight probably won't find it simply by changing their intestinal bacteria. After all, in the second study the bacteria changed after the subjects lost weight on low-fat or low-carbohydrate diets.

What this research does show is that overeating and lack of exercise may not be the only reasons people gain weight. And with the increasing incidence of obesity, especially among children, the more physicians know about the problem and its causes, the better able they will be to treat it.