Overweight and obesity prevalence is increasing worldwide both in developed and developing
countries. In the United States, obesity increased for both sexes, as well as across ages, and
ethnicities [1]. In 2008, 33.9% of American adults was obese and 34.4% was overweight [2].
Moreover in 2010, there was no state in the United States that had a prevalence of obesity less
than 20% [3]. In 2010, 18.1% of Canadians aged 18 and older reported height and weight that
classified them as obese; in addition, 41.1% men and 27.2% women were overweight [4]. In
European countries, the prevalence of obesity was about 10% and the overweight prevalence
was 36.6% and 25.6% among men and women [5]. Individuals in the United Kingdom had the
highest prevalence of obesity (12%), while Italians, French and Swedes had the lowest levels
of obesity (about 7%) [5]. In Asia, the prevalence of overweight and obesity were lower than
the North of America. The prevalence rate of overweight and obesity among Chinese adults
were 21.51% and 2.92% respectively, with higher prevalence seen in the north than in the
south, more in females than in males, and more in older age than in younger [6]. The prevalence
of overweight and obesity among Thai adults was 31.5% and 7.8% (2003) [7]. In Malaysia,
overweight and obesity prevalence were 41.1% and 14.4% (2003) [7].
The prevalence of underweight is low in developed countries but it remains high in developing
countries. The prevalence of underweight is the United States and Canada is 2.4% [7] and 2.0%
[8] respectively. In Asian countries, the prevalence of underweight is very high: 19.2% in
Thailand in 2003 [7]; 9.6% in Malaysia in 2003 [7]; and 20.9% in Vietnam in 2005 [9].
Underweight and overweight are coexisted in all countries around the world; Many developing
countries face the dual challenge of continuing underweight and increasing overweight [10].
Literature focusing on urbanization and health showed that the prevalence of overweight is
significantly higher in urban than in rural areas [11].
Assessment of the socio-economic disparities in underweight, overweight and obesity is
important to addressing health problems. It is widely found that both underweight and
overweight can cause an increased risk of mortality [12]; overweight and obese are associated
with higher risk of having a chronic disease [13], diabetes, coronary heart disease,
hypertension, stroke and cancer [14, 15]. Besides, knowledge of the distribution of weight
status and how weight status may vary by socio-economic factors can provide baseline
information for national monitoring and developing health promotion programs [16].
Vietnam is also facing the dual challenge of a high prevalence of underweight and increasing
overweight [17]. In 2005, the prevalence of overweight following the classification for Asian
and the Pacific population, i.e. BMI ≥ 25 kg/m2
, was 6.6% and the prevalence of underweight
defining as BMI≤ 18.5 kg/m2 was 20.9% [9]. Nonetheless, the data is outdated and such studies
on overweight and underweight are still limited in the country. Information is even more
limited while looking at variations of underweight and overweight by socioeconomic factors
at provincial level.This study aims to shed light on prevalence of underweight and overweight and its variations
by socioeconomic factors in Thai Nguyen province of Vietnam. The province locates in the
northeastern mountainous region of the country and houses many poor and ethnic minorities.