Dec. 14, 2010  -- Amidst the lush landscape and breathtaking natural beauty of Guatemala, more than half the population lives below the poverty line and suffers from chronic malnutrition.

In fact, Guatemala has the highest rate of malnutrition in the Western Hemisphere: 50 percent of the population is stunted and, in rural Mayan villages, that figure gets as high as 80 percent.

The main cause of stunted growth, experts say, is lack of vital nutrients during the first thousand days of life, that critical period of development from conception to age 2.

"The most incredible thing about stunting in Guatemala is how completely total an experience it is for rural communities. All children are at least six or eight inches shorter than they should be," said Peter Rohloff, an American doctor who runs Wuqu' Kawoq, a group of medical clinics in rural Guatemala. "In a family that's extremely impoverished, you will see very extreme cases of chronic stunting where children who are twelve years old, look that they're -- as if they were four or five. "

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But stunting is not just about height. With malnourishment comes greater susceptibility to disease and infection, impaired cognitive function and even lower IQ. Stunted kids are more likely to drop out of school and grow up to be unskilled workers with little potential for economic success later in life.

"If you want to break the cycle of poverty in Guatemala this is how you do it: Feed kids and feed them early before they get malnourished," Rohloff said.

Because a typical Mayan diet is lacking in animal protein like milk, Rohloff encourages mothers to breast feed but also to give their babies supplementary food starting at six months. He teaches mothers how to use Incaparina, a locally made corn gruel fortified with vitamins and minerals that needs to be mixed with just the right amount of water.

The mixture will be useless or even harmful if it is too diluted or the water contaminated. There are better supplements that need no preparation, Rohloff said, like Plumpy Doz, a ready-to-use sugary peanut paste with milk powder and vitamins. Unfortunately, there is no local Plumpy Doz manufacturer and getting the product shipped in can be problematic and expensive.

For nutritional intervention to be most effective, he said, it has to be done before the age of two.

"Unfortunately, most programs in Guatemala are geared to school-aged kids but by the time they get to school it's too late," he said.

Saving Baby Gricelda

In fact, the Mayan poor get few services from a government that is widely considered to be corrupt and ineffective. And in a country where there is a tremendous divide between the rich and the poor, privately funded NGOs like Wuqu' Kawoq and Casa Jackson step in to provide much needed social services.

Casa Jackson is a center for malnourished children in Antigua, run by American Luke Armstrong and staffed by local nurses and doctors as well as volunteers. It's here that you'll find children like Carlos who, at 13 months can barely hold his head up or stand. And then there's Yennelly, who at four months old is the size of a newborn, just 7 pounds.

"Yennelly's mother had little breast milk and could not afford formula so she gave her sugar water," Armstrong said.

In the village of Cajagualten, Luke and his staff run monthly field clinics. They lure parents in by offering free clothes but the real purpose is intervention and education including medical checkups. Doctors are especially on the lookout for babies in distress.

At their November clinic, hundreds showed up, including Maria, a poor Mayan mother of five. Doctors discovered, much to Maria's surprise, that her youngest child , two-month-old Gricelda, was severely malnourished and needed immediate medical care.

With Maria's consent, doctors took the baby to Casa Jackson where she was treated, fed and cared for. In just two weeks, she made remarkable progress. And while the baby recuperates at Casa Jackson, Luke taught Maria better ways of feeding her daughter and better utilizing scarce resources so her child could continue to grow properly.

The American government is here, too, helping out through large humanitarian groups like Save the Children. In rural villages throughout the country they distribute rice, beans and fortified corn soy flour.

But the food is just a small part of what they do, according to Save the Children's Guatemala country director Carlos Cardenas. Their main emphasis is on teaching nutrition and showing poor families how to become more self-sufficient by growing their own gardens and raising chickens. And then there are the goats that provide badly needed milk for malnourished young children.

Mayan Children in America Taller Than Guatemalan Peers

Because almost everyone is stunted in rural Mayan communities, it would seem that Mayans are just genetically short.

But, according to medical anthropologists, this is not necessarily true. Diet plays a critical role.

We compared a group of native 9-year-old Mayans and a group of 9-year-old Mayans raised in the United States. The difference was dramatic. The American Mayan children who have access to better food are, on average, six inches taller than those raised in Guatemala. (See photos below.)

Wuqu' Kawoq, Casa Jackson and Save the Children are all helping to break the vicious cycle of poverty and malnutrition in Guatemala. Though the numbers still seem overwhelming, inroads are being made: Dr. Rohloff said in just 12 months, through nutritional intervention, he was able to cut malnutrition rates in half in the communities where he works.

"That is an extraordinarily exciting thing," he said. "That's an extraordinary accomplishment. To see, small children who now have the chance to live out their true, biological and social potential."

CLICK HERE for more photos of ABC News' coverage of stunting and malnutrition in Guatemala.

The "Be the Change: Save a Life" initiative is supported in part by the Bill & Melinda Gates Foundation.