London, England (CNN) -- Almost 200 million children under the age of five in the developing world suffer from stunted growth, according to a new U.N. report. But surprisingly, in the Middle East, wealthier countries have more of a problem than some poorer nations.
The Occupied Palestinian Territories, for example, have a stunting prevalence of 10 percent -- the lowest in the Middle East -- according to the study from UNICEF, the New York-based United Nations Children's Fund.
Oil-rich Saudi Arabia and the United Arab Emirates, both much wealthier nations, had significantly higher rates of stunting prevalence -- 20 and 17 percent respectively.
Yemen had the highest rate of stunting prevalence in the Middle East -- a staggering 58 percent -- meaning more than half of all Yemeni children under five were significantly short for their age.
"High income from oil doesn't mean the general population is benefitting from it," said Arnold Timmer, senior adviser on nutrition for UNICEF, when asked about the findings.
"Economic development is generally good news for nutrition and for human development," Timmer told CNN. "But what children and mothers eat is not driven by economic indicators, but also by diet preferences, what's available and what's culturally trendy."
Timmer said food choice is a particular problem in the Middle East.
"Instead of exclusively breast milk, the children might be getting a porridge of milk and butter and sugar that doesn't have any vitamins and minerals in it," Timmer said, "or tea."
Timmer said tea is not recommended for young children because it can inhibit the absorption of iron, causing anemia.
Stunting, or low height for age, is caused by undernutrition, the U.N. said.
"Stunting is associated with developmental problems and is often impossible to correct," a UNICEF statement said. "A child who is stunted is likely to experience a lifetime of poor health and underachievement."
The report, entitled "Tracking Progress on Child and Maternal Behavior," said the 1,000 days from conception until a child's second birthday are the most critical for development.
Nutritional deficiencies during these all-important three years impair a child's ability to fight and survive disease and impacts their social and mental capacities for their entire lives.
"Those who survive undernutrition often suffer poorer physical health throughout their lives, and damaged cognitive abilities that limit their capacity to learn and earn a decent income," said UNICEF Executive Director Ann M. Veneman.
"More than one-third of children who die from pneumonia, diarrhea and other illnesses could have survived had they not been undernourished."
Stunting is a greater problem than being underweight or wasting, the U.N. report said. Most countries have much higher stunting rates than underweight rates, it said. In some countries, like Afghanistan, Yemen, Guatemala and Ethiopia, more than half of all children under five years old are stunted.
The U.N. defines stunting as height for age minus two standard deviations from the median height for that age. Wasting is defined as weight for height minus two standard deviations from the median weight for height for that age.
The bulk of the world's undernutrition problem is localized, with 24 countries accounting for more than 80 percent of the world's stunting. More than 90 percent of the developing world's stunted children live in Africa and Asia.
Although India is the country with the highest number of stunted children, it does not have the highest prevalence of stunting, due to its large population. Afghanistan has the highest prevalence of stunting of any country, with a whopping 59 percent.
"Nutrition remains a low priority on the national development agenda of many countries," the U.N. report said. "Despite clear evidence of the consequences of nutritional deprivation in the short and long term."
The report said nutrition problems often go unnoticed by governments until they reach "a severe level." Children may appear to be healthy even when they face grave risks associated with undernutrition, the report warned.
"Not recognizing the urgency, policymakers may not understand how improved nutrition relates to national economic and social goals," it said.
In countries with the highest level of undernutrition, governments are often facing multiple challenges -- poverty, conflict, disaster, economic crises, yawning inequity. Undernutrition only takes center stage when widespread and severe.
The report recommends that of all the proven interventions, exclusive breastfeeding for the first six months of life -- together with nutritionally adequate food from six months onwards -- can significantly impact stunting.
Progress has been made in both Asia and Africa on stunting, the report said. In Asia, the prevalence of stunting dropped from about 44 percent in 1990 to 30 percent in 2008. In Africa, it fell from around 38 percent to an estimated 34 percent over the same period.
But the children's agency warns much more needs to be done.
"Unless attention is paid to addressing the causes of child and maternal health undernutrition today, the costs will be considerably higher tomorrow," UNICEF chief Veneman said.