With the American Medical Association declaring obesity a disease in 2013, there's little denying how serious of a global epidemic the fight against the bulge is becoming. It's a fight, though, that isn't being waged in what I'd refer to as the select few "healthiest countries in the world."

This past spring we examined nine of the most obese countries in the world, according to a report from the Organization for Economic Cooperation and Development, also known as the OECD. Unsurprisingly, the United States found its way to the top of the list with nearly 34% of its citizens weighing in as obese (defined as a body mass index above 30). According to the latest OECD findings, 53% of adults in its survey scope (40 countries) are now considered overweight (BMI of 25 or greater) or obese. 

The seven healthiest countries in the world
But not all countries are struggling with obesity issues. Certain factors have been key in allowing the following seven countries to keep their obesity rates low while other nations have witnessed soaring levels.

Based on the OECD's findings, here are the seven healthiest countries in the world:

Source: Organization for Economic Cooperation and Development.

Of the 40 countries surveyed, only these seven managed an obesity rate of 10% or less. Furthermore, even though these countries offer some of the lowest obesity rates in the world, the majority saw rates increase since the last OECD study in 2000. Japan, South Korea, Switzerland, and Norway have all seen notable jumps in their obesity rates of 60 basis points, 90 basis points, 40 basis points, and 400 basis points, respectively, over the past decade. Only China's obesity rate has remained flat at 2.9%, while no data was available for India or Indonesia in 2000.

Here's why these countries are the healthiest
What are these countries doing that keeps their obesity levels low? Ultimately, the answer may lie with socioeconomic factors that alter eating habits within these nations.

Rice Planting

Planting rice in India, Source: MckaySavage, Fotopedia.

One prevailing pattern that certainly helps keep obesity rates down is a higher prevalence of poverty than the OECD average. According to the organization, about 10% of adults are considered to be in poverty. In India, as of 2011-2012 the Planning Commission calculated the poverty rate to be at 22%! Amazingly enough, that's actually down from the 37.2% poverty rate in 2004-2005 and 29.8% in 2009-2010.High poverty rates limit nutritional food sources and cause citizens to live off rice, grains, and other relatively inexpensive foodstuffs, which keep many from indulging on high fat content foods that we've become accustomed to in the United States.

Another major factor to consider here is that the populations of all seven countries listed above could arguably be considered more active than citizens of the United States. In developing countries such as India, China, and Indonesia, not all citizens have the means to purchase a car, nor is the infrastructure necessarily there to support a large amount of industrialization as of yet. This means citizens in these countries are used to walking and relying on public transportation for their means of getting around. In Europe, public transportation is considerably better than that of the U.S., allowing many people to go without owning a car and simply rely on walking, buses, and subway systems for their transit needs.

Finally, there's a factor of what citizens in these countries eat as well. In Korea and Japan, for example, poverty isn't as big of an issue, but Korean and Japanese diets tends to be very low in fat content. Compare that to the U.S. where you can find a fast-food establishment on practically every corner, and the difference is night-and-day.

Here's why you should care
Another question potentially popping into your mind might be, "Why should I care?" Because for investors, the OECD figures can point toward two ways to use obesity data to get rich.

On one hand, countries with higher than average obesity rates could be perfect targets for weight control management drugs such as Belviq from Arena Pharmaceuticals (NASDAQ:ARNA), Qsymia from VIVUS (NASDAQ:VVUS), and even the experimental drug Contrave from Orexigen Therapeutics (NASDAQ:OREX).

As I described in May, each company brings its own unique positives to the table that could make any of these three, or all three for that matter, wildly successful. In trials, VIVUS' Qsymia was tops at delivering the greatest amount of weight loss in percentage terms, while Arena's Belviq delivered the most favorable safety profile of the two FDA-approved drugs. Contrave, by contrast, is being reviewed by the Food and Drug Administration, but it has also completed a long-term safety study (the Light Study) that demonstrated no adverse effects on patients' cardiovascular health. That could put Contrave in the fast lane to approval in both the U.S. and Europe and leave Arena and VIVUS in the rearview mirror.

Just as we can target countries with high obesity rates, these lower-obesity countries also give us an intriguing opportunity. Rather than looking within the pharmaceutical sector for our investment opportunity, we instead look toward poverty and economic inequality to help guide our investment. In other words, we need to improve crop yields so those who are impoverished have the ability to get a healthy amount of food in front of them each day.

Two names that could play an integral role in improving crop yields around the world are CF Industries (NYSE:CF) and Terra Nitrogen (NYSE:TNH).

CF Industries is a phosphate and nitrogen-based producer of fertilizer, while Terra Nitrogen, as the name implies, deals with the production and sale of nitrogen-based products. Although prices for fertilizer were down in the dumps in 2013, this swoon appears temporary, as a growing number of people on this planet will push farmers around the globe to improve yield at almost any cost. Terra Nitrogen, which is a master-limited partnership, should continue to deliver impressive dividends to shareholders (it paid out $14.35 per share in 2013), while CF offers perhaps the best global product diversification of the group and also recently announced a dividend hike.

This transformation could have a big impact on the fight against obesity
Domestically, Obamacare is expected to revolutionize the health care system, including the way we see physicians and access our medication, such as weight control management drugs. Obamacare may seem complex, but it doesn't have to be. In only minutes, you can learn the critical facts you need to know in a special free report called Everything You Need to Know About Obamacare. This FREE guide contains the key information and money-making advice that every American must know. Please click here to access your free copy.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

The Motley Fool owns shares of CF Industries Holdings. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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