Why do we get fat
So boom, why do we get fat? Simple question. And the answer is pretty obvious also, as the NIH puts, obesity occurs when a person consumes more calories from food than he or she burns, okay. It’s conventional wisdom – energy in is greater than energy out. Okay, we overeat. Simple enough.
This is the energy balance hypothesis of obesity. That’s how it’s known. We take in, it’s calories in, calories out, whenever you hear somebody say that a calorie is a calories, is a calorie. This is what they’re arguing, and any food will make you fat if you take in more but then you’re expending.
So I just want to ask a question – how many of you believe this is true? Just so I get a feel for – okay, 13 people.
I am going to argue that this is one hypothesis of obesity and there are alternatives. And that obvious as it seems, what we want to do is look at the alternatives and see because this is science. Maybe the alternatives explain the observations better than our energy-in, energy-out hypothesis. So again this is kind of how it’s perceived today in the popular press.
Energy-in greater than energy-out
And one of the things you want to do as a science is we want to explain, not just obesity but the obesity epidemic. So science is about observing things and then figuring out what the causes are, and our explanation for the obesity epidemic is increased prosperity. This is a phrase that the NYU nutritionist Marion Nestle used in a Science article 10 years ago when Marion is still arguing, so the idea is we get richer and as we get richer food is more available. We have to exercise less, basically the food and entertainment industries conspire not consciously but subconsciously to feed us too much and give us too many opportunities to be sedentary watching TV, watching video games, or kids are playing video games or are on the iPads everyday. They’re not outside running.
Kelly Brownell, a Yale psychologist used the phrase the toxic environment to describe this, and toxic environment is an environment that promotes sedentary behavior and overeating. And by doing so makes calories in, more than calories out, as Kelly put it your cheese curls and french fries, drive-in restaurants are more part of environment now than trees, grass and clouds. Your children sit at home and watch television, they play video games as parents are afraid to let them walk or bike to school anymore. So we drive them to school. So there’s all these opportunities to eat too much and expend too little and that’s the toxic environment that we live in today.
And the question we could ask as scientists is pretty simple. We have our hypothesis – increased prosperity leads to overeating. Energy in greater than energy out. And the result is the obesity and the obesity epidemic.
And what we want to do is say, does this hypothesis make sense? Does it explain the observations? Because that’s again what we want our hypothesis – we want it to explain things that we see and it certainly seems to explain what we see today.
But there are some less obvious observations out there, and this is what I did in the course of my research, as I was able to go back in time and looked for examples for populations that had high levels of obesity. But none of the toxic environment that we see today around us.
Pima Indians- History of Obesity
And the first is on the Pima Indians – Native American tribe that live in, on a reservation today in Arizona, south of Phoenix. And the Pima were happened to be among the most affluent Native American tribes through the middle of the 19th century. So they were hunters and gatherers. They hunted in the nearby mountains. They fished in the Gila river. They farmed, they were an agrarian population as well. So they raised wheat and beans. They raised pigs and cattle.
And in late 1840s when army battalion started traveling through the Pima territory, they noted that the Pima were sprightly and in fine health. And they had this great abundance of food, warehouses full of foods so much so that after gold was discovered here in California in 1849, and from the 1850s to 1880s, 20,000 to 60,000 49ers went west on the Santa Fe Trail that lives in the Pima territory. And the US government asked the Pima to feed them which they did.
So in 1846, they were very prosperous tribe and they were described the sprightly and fine health by several observers. This drawing was actually made in 1851.
And then what happens is Anglo Americans and Mexican Americans are moving into the Pima territory in Arizona and they over hunt the local mountains and they divert the Gila river water to irrigate their own streams. And by the 1870s, the Pima are starving. And they go through 20 to 30 years of famine.
And by 1902, a Harvard anthropologist named Frank Russell comes to live with the Pima, and he describes the conditions on the reservation as poor beyond our imagination. They’re trying to make a go at farming and barely doing it. And Russell takes this picture of this Pima Indian that he calls fat Louisa. And he says there is a degree of obesity on the tribe, particularly in the older people completely at odds with the popular image even back then of the Native American lean handsome Native American and popularized thought.