FP Explainer

Why Do the World's Fattest People Live on Islands?

It's not piña coladas. Evolution has been overwhelmed by Western lifestyles.

Last week, a study published in the British medical journal The Lancet found that worldwide obesity rates have increased significantly over the past three decades. By far, the greatest increase was in the Pacific islands. In the world's fattest country -- Nauru -- the average body mass index (BMI) is now an off-the-charts 35.03 for women and 33.85 for men. (Above 30 is generally considered obese.) The Cook Islands, Tonga, Samoa, French Polynesia, and Palau aren't far behind. Several Caribbean islands-- including Bermuda, Puerto Rico, and St. Kitts and Nevis -- are also in the obese category. Of the 13 countries with average BMIs over 30, only Kuwait and Egypt (where just the women average over 30) aren't islands. (Although the United States, with average BMIs of 28.33 for women and 28.46 for men, is well on its way.) So why are island countries so obese?

It's a combination of factors including diet, lifestyle, and culture -- but the main culprit is globalization. Most of the Pacific islands were traditional societies, dependent on subsistence farming and fishing until the mid-20th century. The arrival of U.S., French, and British militaries during the Pacific campaigns of World War II began a monumental shift, as the countries opened up to the world. Large-scale industrialization of the Pacific islands didn't begin in earnest until the 1970s. The result was that the South Pacific had only about 40 years to adapt to the kind of modern, sedentary lifestyle that people in the West have been getting used to for centuries. (The Persian Gulf states, which are also struggling with obesity and its related health conditions, have had a similarly rapid transition to modernity.)

The ready availability of imported food has coincided with the conversion of farmland to more lucrative industries such as mining. Nauru's land area has been almost entirely turned over to phosphate mining, forcing its people onto a tiny sliver of livable land. While the traditional Pacific diet was dominated by fish, fruits, and vegetables, Nauru's islanders have now developed a taste for imported rice, sugar, flour, soda, and beer. (Spam is a particular favorite.) Western fast-food outlets have also arrived along with the island's growing tourist industry.

Many researchers also believe that Pacific islanders' bodies are genetically hard-wired to store fat more efficiently. This trait used to make a lot of sense -- living on a tiny island, highly susceptible to the effects of the weather, often involved long periods of famine and required a great deal of physical labor. But that's not quite the case anymore in a world of retail jobs and Big Macs. (People of African descent are also thought to be prone to retaining weight, perhaps a reason why the inhabitants of Caribbean islands are becoming increasingly obese.) Culture also plays a role. A large physique is also often considered attractive in Pacific island societies -- a mark of higher social status -- but you no longer need to be a chief to eat like one.

Of course, these factors are present in many other developing countries. What really sets the size of these islanders apart is the size of their islands: Tuvalu, Palau, Nauru, and the other countries on the obesity list are among the world's smallest countries in terms of land area and population. So a single tourist resort, fast-food chain, or trade deal has a much more profound effect on society than it would, say, in India or Nigeria.  

Obesity may seem like a small price to pay for access to the modern world and all its comforts and opportunities. But conditions associated with obesity are starting to take their toll. In Nauru, an estimated 45 percent of adults may be diabetic. Life expectancies, which rose throughout the region for decades, have begun to plateau in recent years because of weight-related health problems.

The situation isn't hopeless. Education programs encouraging people to eat local, healthier foods have helped bring obesity rates down in Tonga, Fiji, and Hawaii. The Aloha state -- birthplace of famously skinny President Barack Obama -- is actually one of America's trimmest.

Thanks to Richard Taylor, professor of public and international health at University of New South Wales.

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FP Explainer

How Do We Know How Many Protesters Came Out in Cairo?

We don't really.

Organizers of Egypt's protests called for a million demonstrators to come to a rally at Cairo's Tahrir Square on Feb. 1, but actual estimates of crowd size have varied widely. Al Jazeera reported a crowd of "more than a million." The AP was more conservative, using "more than a quarter-million." The New York Times was vague, describing "hundreds of thousands" filing into Tahrir Square. How do they come up with these numbers?

They're probably guessing. The most widely used method of counting crowds was developed by the U.S. National Park Service in the early 1970s and relies on three factors: the size of the space where the event occurs, the amount of the space occupied by the crowd, and the density of the crowd. Crowd density can vary from "mosh pit" close -- one person for every 2 feet -- to the more common one person for every 5 feet -- your standard Tea Party rally. It's nearly impossible to get an accurate count from the ground because of an optical illusion called foreshortened perspective that makes crowds closer to the observer appear denser than they actually are, so aerial photos are generally needed.

U.S. newspapers still use a variant of this method, though the Park Service has been prohibited by Congress from releasing its own numbers since 1995, when Million Man March organizer Louis Farrakhan threatened to sue the agency for estimating the crowd size at around 400,000.

For preplanned, organized events like presidential inaugurations or the recent rallies on the Washington Mall held by Glenn Beck and Jon Stewart, news agencies contract with aerial analysis firms like the Virginia-based Digital Design and Imaging Service to get the most accurate numbers possible. Digital Design makes a computer model of the space divided into a grid. Then a balloon mounted with nine cameras is tethered over the crowd and takes photos at different altitudes and vantage points. Organizers generally try to schedule these surveys for the high point of the event, such as when Sarah Palin spoke during Beck's "Restoring Honor" rally. Digital Design then comes up with multiple numbers based on mathematical modeling, hand-counting heads within a given quadrant, and guesstimates from academics who study crowd behavior. The numbers are then averaged out. 

Estimating gets exponentially harder in a more spontaneous and chaotic event like the Tahrir Square rally. The event was called only a day before, so obviously computer models and weather balloons were out of the question. The most accurate aerial photos of the event come from satellites, which means that images can be taken only when the satellite is directly overhead and when the square is not obscured by clouds. This makes it extremely difficult to get multiple images and to judge when the crowd is at its height.

Using a simplified version of the Park Service methods, analysts at the private intelligence firm Stratfor found that even the AP's 250,000 number is pushing it. University of Illinois sociology professor Clark McPhail estimated that Tahrir Square itself could probably hold a fairly dense crowd of around 100,000.

Of course, Tahrir is essentially a giant traffic circle with multiple feeder streets, also choked with people -- and news reports Feb. 1 stated that protesters were fanning out throughout the city. Because the demonstrators were not necessarily marching in one particular direction and were pushing through vehicles, police, and other impediments, a reliable estimate for the total number of people in downtown Cairo becomes mostly a matter of guesswork.

Even using the vaguest criteria, however, Al Jazeera's estimate seems extremely generous, though that was presumably of little comfort to President Hosni Mubarak as he announced his impending departure from power.

Thanks to Curt Westergard, president of Digital Design and Imaging Service, and Clark McPhail, professor emeritus of sociology at the University of Illinois.

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