Tom Barnett is a self described strategic thinker. His focus is on what is likely to happen several years down the road, whether its political, military, demographic or whatever. It’s sometimes difficult for me to worry about what might happen several years away when the here and now is driving us up the wall. But Tom has a way of crating clarity in a confusing world and all of this will influence how I help my clients manage their money and their lives, not to mention my life.

This post of Tom’s is part of a recurring theme of his that suggests food and the availability of it will increasingly dictate how the world interacts with us as a nation and how we should respond. Here are his comments about The New Rules.

The real clash of civilizations in the 21st century will be not over religion, but over food. As the emerging East and surging South achieve appreciable amounts of disposable income, they’re increasingly taking on a Western-style diet. This bodes poorly for the world on multiple levels, with the most-alarmist Cassandras warning about imminent resource wars.

But the more immediate and realistic concern is the resulting health costs, which will inevitably trigger a rule-set clash between nanny-state types hell-bent on “reining in” a number of globalized industries — agriculture, food and beverages, restaurants, health care and pharmaceuticals — and those preferring a more free-market/libertarian stance.

This clash won’t necessarily pit East versus West or North versus South, or even democracies versus authoritarian regimes. The core of this struggle will be about sustainability versus individual freedom of choice, because, as a recent Financial Times editorial put it, “Individuals have a right to indulge in excesses, but they also have responsibility for costs.”

Of course, we’re already used to hearing that kind of talk with regard to the usual suspects, like tobacco use and drug abuse. But what about when soft drinks, salty potato chips, sugary confections and fatty cheeseburgers all go onto the “sin tax” list? Sound incredible? Several U.S. states recently considered doing just that to triangulate rising health care and eldercare costs with looming fiscal constraints. Meanwhile, for the first time in its history, the United Nations just debated the social burden of noncommunicable diseases, otherwise known as lifestyle choices.

Several global trends are converging to make humanity’s preferred diet a compelling issue in the 21st century.

First, medical advances mean babies are surviving to age five in far greater numbers worldwide, and thus people are living dramatically longer. As all the communicable diseases that used to wipe out so many people in underdeveloped economies increasingly come under our collective control, these populations join those in the advanced West in succumbing largely to lifestyle diseases, or the Big Four global killers: heart and respiratory diseases, cancer and diabetes.

The four best ways to reduce the risk factors for the Big Four are also well known: cutting out tobacco and too much alcohol, exercising regularly and eating properly. Tobacco and alcohol have long been subject to sin taxes. But requiring citizens to exercise is a tough goal for nonauthoritarian governments to pursue, so that leaves some sort of regulation for “bad” foods and beverages as the only avenue left.

The second reason why foods and beverages will be targeted is because rising global demand will keep worldwide supplies of agricultural commodities unusually tight from here on out. As an emerging global middle class moves up the caloric chain, demographically burdened economies like China and India are highly incentivized to leap-frog past the environmentally and medically unsustainable Western diet to something more manageable. Otherwise, public and private sector investment that could go to urbanization, industrialization, education, research and development, and other worthy sectors will instead be sucked up by those incredibly expensive “remediation” efforts.

A third complicating factor is climate change, which will make it harder to grow food in those regions least able to feed themselves today and set to experience the highest population growth rates in the years ahead. For a lot of countries, that will make food security an increasingly larger part of their perceived national security — otherwise known as regime security. Remember, the Arab Spring was preceded by a year or so of rapidly rising prices for basic foodstuffs. That’s why so many Asian and Middle Eastern nations are busy leasing or buying up farmland overseas. And governments that have made that level of national effort can be expected to become more bossy about what their citizens eat.

Finally, global obesity — or “globesity,” as the World Health Organization has called it — is becoming the WHO’s cause célèbre, with the U.N. organization now ranking it up there with tobacco use and AIDS in terms of negative global impact. In many ways, globesity is the sum expression of globalization’s rapid expansion: Blossoming car cultures reduce exercise while ramping up pollution; the resulting climate change makes it harder to grow all the extra food that humanity now demands; rising incomes mean more people get to eat meat and drive cars, diverting more grains to cattle field and ethanol, and resulting in fatter and less-healthy individuals more given to driving than walking. Let’s agree to call it a vicious cycle.

The WHO says about one-quarter of the world is overweight, but truth be told, most of those afflicted are found in the West for now, while most of those suffering from malnutrition are found in the South. But before we reach for the “Soylent Green” DVD, it bears noting that we’re increasingly seeing obesity alongside famine in developing economies, which tells us that things are going to get a whole lot worse as per capita incomes continue to rise in regions outside the West. China is a prime example: The current generation of “only children” is the fattest on record, prompting the Chinese government to repackage Chairman Mao’s radio-broadcast calisthenics programs to fight the expanding flab.

Frankly, this is an area where America should get out into the lead. We have one of the highest obesity rates in the world, along with the healthcare costs to prove it — and yet we’re one of the world’s great food exporters, which should make us nervous about the potential for “food nationalism.” Before our products start being turned away in foreign markets due to their negative health impact, we should start weaning ourselves off of those foods and beverages that have so radically ramped up our obesity rates over the past few decades. In this effort, the government has a role to play: As always, incentives tend to work better than punishments, but a little hectoring helps too. A lot of critics brushed off Michelle Obama’s recent efforts along these lines when they shouldn’t have: Better the message comes from “big mother” than Big Brother.

Globalization’s great gift to humanity has been to move so much of the world’s population from subsistence to abundance, but by extension that means that we must collectively revolutionize our resource-utilization models to manage this unprecedented success. How we feed ourselves is the logical place to start, because in a globalized world, we must multiply the maxim, “you are what you eat,” by 7 billion. And that will soon have a cumulative impact on our planet that we cannot afford to ignore.

Thomas P.M. Barnett is chief analyst at Wikistrat and a contributing editor for Esquire magazine. His forthcoming eBook serial is “The Emily Updates: One Year in the Life of the Girl Who Lived” (September-December 2011). His weekly WPR column, The New Rules, appears every Monday. Reach him and his blog at thomaspmbarnett.com.