Thin can be contagious - really!

In the old days, our moms would paint our scratches and nicks with Mercurochrome or, heaven forbid, Merthiolate, which stung like the devil. The goal was to hold the germs at bay. We had a pretty clear idea that our skin was a clear dividing line between that which is us and that which is not. And germs of all kinds were to be kept out.

But to our surprise, we are increasingly finding that some germs, species of bacteria called gut flora in particular, are not only harmless but downright beneficial.

The human digestive system contains trillions of bacteria weighing in at two to four pounds and actually outnumbering the human cells in our body. Gut flora help us process nutrients, harvest energy, create certain vitamins, and provide protection from pathogens. This symbiotic relationship is very complex, one of which we are still just scratching the surface.

Now a new study (Science, September 6) has given us a fresh sense of wonder about our tiny cousins. The surprising finding is that, not only do fat people and thin people have different species of bacteria in their guts, but those bacteria can actually influence obesity.

The study centered around a set of rare human twins, one of which was fat and the other thin. When laboratory mice received bacteria from the obese twin, they started to become fat. Mice receiving bacteria from the lean twin stayed thin. Here is the really interesting part: when the mice were comingled and bacteria in their guts were able to compete, the “thin” bacteria won the competition, infected the guts of obese mice, and kept their new hosts from gaining weight.

So far so good. But if these thin bacteria are naturally dominant, why aren’t there raging epidemics of leanness spreading across the continent?

The answer is diet. The thin bacteria were dominant when the mice were fed a low-fat, high-fiber diet. But when researchers changed that to a high-fat, low-fiber diet (more typically American ), the thin bacteria lost their dominance. They were still able to keep lean mice thin, but they were unable to establish a presence in the guts of obese mice.

The research is promising and bacterial weight therapy may be in our future. But, unfortunately, nothing that will overcome a diet of cheeseburgers and fries.

Why do we care? Because the negative effects of obesity are so severe. The CDC cites research showing that when weight increases to “overweight” or “obese,” the risk of the following conditions rises significantly:

•     Coronary heart disease
•     Type 2 diabetes
•     Cancers (endometrial, breast, and colon)
•     Hypertension (high blood pressure)
•     Dyslipidemia (for example, high total cholesterol or high levels of triglycerides)
•     Stroke
•     Liver and Gallbladder disease
•     Sleep apnea and respiratory problems
•     Osteoarthritis (a degeneration of cartilage and its underlying bone within a joint)
•     Gynecological problems (abnormal menses, infertility)

The health effects are enormous; the impact on quality of life is tragic. And the economic impact is huge, estimated at $147 billion per year. Now that we are all in the same taxpayer-subsidized health insurance risk pool, that should make you take note.

Michelle Obama is right. As a nation, we need to begin moving to a diet which is more low-fat and high-fiber on average.In fact, if we were all to pretend we were pre-diabetic and took up a low GI (glycemic index) diet, our collective weight loss would be measured in megatons.

An apple a day, indeed, may keep the doctor away.