Among the things to celebrate this holiday season is the fact that there are fewer hungry people in the world. Just how many? Well, since 1965, researchers in Europe have been tracking the world's food supply and where it's going.

The good news is: The percentage of the world's population getting what the researchers say is a sufficient diet has grown from 30 percent to 61 percent.

In 1965, a majority of the world survived on less than 2,000 calories a day per person. This was especially true in parts of the Middle East, Africa, Latin America, China and Southeast Asia. Now, 61 percent of the world has access to 2,500 or more calories a day.

But one thing the scientists discovered is that the countries that have a history of food insufficiency didn't just up and start growing lots more food. Instead, for the most part they're increasing supply by importing food from abroad.

Cross-border trade in food has skyrocketed in the past 50 years. The major exporters have been the U.S., Canada, Australia and Argentina. Brazil, once a place with its own food deficit, is also a major producer of food grown just for export.

And as the supply of food in previously hungry nations has increased, so has consumption of animal-based food. In fact, worldwide, the supply of calories from animal-based nutrition has increased 2.6 times.

Writing in the journal PLoS, the researchers, from Finland and Germany, note that the increase in food production may strain natural resources in some places as more land is put into agriculture, more fertilizer and pesticides are used, and more energy is needed to produce and ship food.

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