Nov. 5 (UPI) -- Young adults in the United States are among the world's heaviest with a body-mass index of 25.4, an analysis published Thursday by The Lancet found.
This suggests they are among the global leaders in a key indicator of poor overall health, the researchers said, as a BMI of 25 or above is considered overweight for adults, according to the U.S. Centers for Disease Control and Prevention.
BMI is calculated by taking a person's weight in kilograms and dividing it by height in square meters. It generally is viewed as the most accurate method for measuring body weight in the context of height to identify those who are overweight or obese, the CDC said.
"National nutrition and health programs should be extended to older children and adolescents to enable healthy growth and development," Majid Ezzati, co-author of the Lancet analysis, said in a statement.
"We need to improve access to affordable, healthy foods at school and in the community both, through healthy food vouchers and free healthy school meal programs for low-income families, and to protect children from unhealthy foods through regulations and taxes," said Ezzati, professor of global environmental health at Imperial College London.
The average BMI among 19-year-olds in the United States, 25.4, places them just outside the global Top 10 of nations ranked by BMI.
Average height and BMI in countries reflects the quality of nutrition and healthiness of the environment during childhood and adolescence, and are important indicators of health and development, Ezzati and his colleagues said.
BMI accounts for weight gain due to being taller, and therefore measures having healthy weight for an individual's height versus being overweight or underweight, the researchers said.
Having low height or excessively low BMI increases the risk of illness and premature death, impairs cognitive development and reduces educational performance and work productivity in later life, they said.
Similarly, high BMI in childhood and adolescence has been linked with a greater risk, and earlier onset of, chronic diseases like type 2 diabetes and high blood pressure.
For this analysis, Ezzati and his colleagues analyzed physical growth trends for 200 countries worldwide over the past 35 years, using data from 2,181 studies on more than 65 million children and adolescents ages 5 to 19.
The researchers focused on 19-year-olds in order to track how height and BMI through childhood and adolescence impact these indicators of health into adulthood, with 19 marking the end of "school ages" and the beginning of adulthood in most countries.
The countries with the tallest 19-year-olds included the Netherlands, Montenegro, Iceland and Denmark, the researchers said.
Countries with the shortest 19-year-olds were in South Asia and Southeast Asia, Latin America and East Africa, they said.
The highest average BMIs among 19-year-olds were found in the Pacific islands, the Middle East and the United States, while "unhealthy growth trends" -- with too little height gain and excess weight gains -- were seen in New Zealand, the United States, Malaysia, Mexico and sub-Saharan Africa, researchers said.
At the other extreme, the BMI of 19-year-olds was lowest in countries in south Asia and east and central Africa, the researchers said.
Growth patterns were healthiest -- with a larger gain in height than BMI -- for girls living in South Korea, Vietnam and Saudi Arabia, among others, and for boys in Central Europe and Western Europe, they said.
American 19-year-olds had the 16th-highest BMI worldwide and ranked 47th in height, the data showed.
"These massive global disparities reflect the imbalance between successful efforts to improve nutrition and growth during the early years compared with school-aged children and adolescents, who have been largely overlooked in many countries," Ezzati said.