Also: why it’s good to be cautious about study-based news stories.
As we noted last week, at this time of year, millions of Americans put themselves on diets, so it’s no big surprise to find books like Travis Stork’s The Lose Your Belly Diet, doing well on the New York Times Best Sellers list.
It’s also no surprise to see the media picking up on our fascination with losing weight, and part of this most recent onslaught of interest has come about through an intriguing paper published just last week in the journal Cell Host & Microbe.
In case you don’t have a subscription, and since we’re pretty certain you won’t find a copy in your local supermarket checkout line, we thought it might be interesting to report on it, investigating in a little more depth than you may find in other sources.
As ever, once you start looking under the hood of a paper, there’s some fascinating learning (as well as a few caveats) to be had along the way.
The headline finding of the research is that there appears to be evidence that switching from a typical unrestricted American diet to a more healthy calorie-restricted plant-based diet may not get an immediate response from your body.
In “pop” terms, going on a profoundly different diet may not deliver instant results.
Let’s begin by checking on the provenance of the study, and this one’s good. In fact, they don’t get much better.
It was led by Jeffrey Gordon of Washington University School of Medicine.
Professor Gordon runs the distinguished Gordon Lab in Washington and has been responsible for some of the research community’s most important work on human gut microbial communities. He also played a pivotal role in the foundation of the Human Microbiome Project.
So how did Professor Gordon’s team go about this new investigation?
Well, they began by inoculating gnotobiotic mice (animals that had been bred to be “germ-free”) with fecal matter sampled from two different groups of humans.
The first group were individuals consuming what might be considered a standard American diet, typically defined as one that’s low in vegetables, fruits, poultry, seafood, and whole grains but high in carbohydrates, saturated fats, red meats, sugar, and processed food.
You know, all the things that are bad for you and none of those that are good for you.
The second group of participants were eating the aforementioned “healthy, calorie-restricted, plant-based diet,” and stay tuned for more about them in a minute: it gets interesting.
Once the mice were dosed with one of two types of human fecal matter, which we’ll term “American” or “calorie-restricted,” the two groups were again subdivided, and placed on either a simulated American or calorie-restricted diet.
Mice with a microbiome they’d inherited from calorie-restricted humans responded strongly to both types of diet.
Mice with an American microbiome, however, responded only partially to being fed the calorie-restricted diet.
Their American microbiome appeared to prevent the calorie-restricted diet having much of an effect.
But wait, who were the individuals who supplied the calorie-restricted fecal samples?
Well, we said it gets interesting, and in fact they were all members of an intriguing organization known as the Calorie Restriction Society, founded in 1994.
Members of the society take the view (and these are their words, not necessarily ours) that the only valid life extension method that has any proven scientific backing behind it is calorie restriction – the consumption of a diet with adequate quantities of all essential nutrients, except that the energy content of the diet (its caloric intake) is safely reduced by as much as 10-40% below the amount of energy (calories) that the body would tend to naturally desire.
In fact, the group members who participated in this study habitually consumed nearly 50% fewer calories than their American diet counterparts.
Somewhat extreme, you may agree.
But while it makes a ton of sense for researchers to investigate such clearly defined individuals, perhaps it’s less reasonable for the mainstream media to then extrapolate this to suggest that individuals modifying their diet – a little – won’t see results?
Actually, the second stage of the research was also deeply interesting.
When mice with the American microbiome were co-housed with calorie-restricted animals, the former gradually acquired some of the bacteria from the latter.
In fact, the researchers went on to argue that we need to think of our microbial communities not as isolated islands, but as part of an archipelago where bacteria can move from island to island.
However, lest you imagine that humans might therefore lose weight simply by hanging out with lean individuals – through some kind of airborne bacterial osmosis – the researchers noted that the mice in the experiment were actually, uh, coprophagic.
Yup, they were poop-eaters.
We’ve not seen any mainstream media coverage of the study mention this, but it’s a good demonstration of the care that’s required when taking perfectly legitimate, completely sound research, and jumping to sometimes unlikely conclusions.
If you want to lose weight this New Year, following Michael Pollan’s simple rule “Eat food. Not too much. Mostly plants.” may make sense for many, and, in fact, one conclusion we can pretty safely take away from this recent research is that the increased microbial diversity of the calorie-restricted individuals seems at least partly based on their higher consumption of fruit and vegetables.
Probably best steer clear of the whole coprophagia thing, though.
Unless you’re a mouse.