Researchers in the United Kingdom have found that a child exposed to antibiotics before the age of six months is more likely to become obese in later childhood and adulthood. More broadly, it means that the child’s energy metabolism has been harmed by antibiotics. It’s a mystery to me why this surprises anyone.

Fifty years ago, ranchers discovered that giving cattle a low dose of antibiotic increases their bulk and with it their market value. Since then we’ve also found that those antibiotics don’t stay in the animals but get spread throughout the environment, doing more than increasing the resistance of pathogens to treatment. And, of course, the antibiotics that do stay in the animal are passed on to humans such as six month old babies.

Last week, researchers at the University of Chicago answered the question, “How come?”

One would think that the metabolic disruption was the result of killing off a portion of the infant’s gut bacteria. Although true, it’s only half the picture. As you might know, your gut bacteria are in intimate communication with your immune system. A disruption in your immune system by itself can cause an imbalance in your gut microbiome and with it a disruption to your energy metabolism. It’s also true that your diet will change the ecology of your gut microbiome.

So the way this works is…

On one side, something such as a change in diet or the use of antibiotics changes your gut ecology. On another side, your immune system responds to that change. And on yet another side, your ability to absorb nutrients is affected depending on how your immune system works. The specific thing at work is an element of the innate immune system (which is the non-specific, non-antibody, first line of defense against potential threats).

The element is called lymphotoxin but was formerly called tumor necrosis factor beta, a cytokine responsible of clearing disruptive gut bacteria. If that part of the immune system isn’t working right, your energy metabolism is destabilized. And when that happens, your body doesn’t do what it’s supposed to: use the nutrients it needs and get rid of the rest.

This is a good lesson in the first law of ecology: everything is connected to everything else.

It also makes a mockery of the so-called energy balance equation used by every popular work and much of the conventional scientific work on weight gain and loss and energy metabolism generally. The energy balance equation says that calories eaten must equal calories used plus calories gained or lost in body fat.

What the University of Chicago research says is that, given one state of the immune system, calories eaten, however many, will equal calories used plus calories excreted with no weight gain. In another state of the immune system, the balance between calories used, calories gained, and calories excreted can be something else—including dramatic and unexpected weight gain.

But that wasn’t the message delivered in the press. In reporting on the research, the University of Chicago PR department and with it the media prominently promoted the idea that now vaccines and antibiotics can be developed to fine-tune the gut microbiome and immune system to treat obesity.

This is appalling.

Here’s an opportunity to re-examine a critical health issue, but instead it gets filed away with conventional technologies. In environmental economics we call such things end of the pipe technologies. The idea of using vaccines and antibiotics to cause an out-of-balance gut microbiome to re-balance itself is at the end of the pipe. Shouldn’t we instead be thinking about what we eat and what we’re exposed to that disrupts our innate immunity? That is, things at the beginning of the pipe?

Of course, it goes without saying the no one is going to think about the unintended consequences of fine-tuning our energy metabolism with vaccines and antibiotics because, as we all know, these are tried and true technologies that have been around for almost a century and nothing bad ever happens from their use. Except of course for the babies who will get fat because they were exposed to an antibiotic through, among other sources, animals that were fattened for market.