The nutrition transition definition is basically according to changes in the quality and quantity of dietary patterns and behaviors in a population. These changes also involve some lifestyle-related factors including general health, work environments, physical activity and socioeconomic situation, all of which ultimately influence energy consumption (Rouhani-Tonekaboni et al., 2018). The current status of nutrition transition in Iran is characterized by high consumption of energy categorized as fat, fast foods and sugary foods, less physical activity and low fiber intakes (Popkin, 1993). In the current study, the authors evaluated the aspects of nutrition transition and its related changeable and unchangeable risk factors that contribute to higher burden of non-communicable diseases (NCDs) among the Iranian population.
Population and mortality changes
Improving global and regional public health is possible via improving in nutrition, vaccination, and perfect sanitation which leads to lowering infant mortality and increasing life expectancy. After the Islamic Revolution of 1979, Iran developed some policies to decrease birth rate, and after the Iraq war against Iran, some plans changed and led to an increased growth rate. Based on the data obtained from Iran Statistics Center (ISC), Iran’s total population is 83 million people, while it is estimated that the total population size will reach to 92 million people in 2050 and then be reduced to 70 million in 2100. Accordingly, Iran has a large population size ranking 19th to 26th between 2050 and 2100 (United Nations, 2015b) . Over the last few decades, the fertility rate has reduced due to some preventive strategies like family planning programs which were administered by the government, increased women’s literacy, increased marriage age, reduced child mortality rate, increased life costs, and pregnancy control by women (Abbasi-Shavazi, 2001, Abbasi Shavazi and Hosseini-Chavoshi, 2011, Ghobadi, 2010, Mirzaie, 2005, World Bank, 2010). Furthermore, it is demonstrated that the growth rate in Iran has been reduced in the last three decades and reached to about 1.2% in 2015-2020. It has been estimated that the growth rate would reach 0% by 2050, and after that, it will be negative (Figure 1) (United Nations, 2015b) . Since 2000, the Total Fertility Rate (TFR) of Iran was less than 2.1; however, it is estimated to be positive by 2050 (Figure 1) (United Nations, 2015b). The age range of the majority of population (̴ 70%) by the year 2020 will be 15–64 years old, and the median age about 32.4; the median age will be continuously increasing to 44.7 in 2050 (United Nations, 2015b) . In 2010–2015, the life expectancy of the Iranian population was about 75, and based on the World Population Prospects (WPP), it will be approximately 80 years in 2050 (United Nations, 2015b) .
Economic and socio-political context
There are considerable disparities of wealth and income in Iran; previous studies have shown great economic inequalities in Iran, particularly between rural and urban areas (Heslot, 2014). The total unemployment rate is 12%, while 30-40% of the youth are unemployed (Heslot, 2014). There are some accumulated resources, in old age, regarding socio-economic security and welfare, including income from work, family support, employers' comfort, owning pension savings, and other benefits such as health coverage and insurance (Mehri et al., 2020). On the contrary, the Iranian old-age economic situation is different in comparison with the above sources, and there is not a citizen-based pension like western countries such as the United States and Europe. Therefore, rich people are relying on their origins, but middle and low-income groups rely on their family and government supports (Mehri et al., 2020). However, there is some support and pensions for specific employees who worked in certain private or government organizations. Some of them are Boniyad Shahid Foundation, Komiteh Emdad Emam, and Astan Qods Razavi. Furthermore, low-income groups receive a monthly cash transfer of 450,000 rials (3 USD) (Mehri et al., 2020). Likewise, the income of the top decile of the population is 15-20 times higher than the bottom one, showing a great inequality of income distribution among the Iranian population (Ghassemi et al., 2002). Other studies revealed that Iran has acceptable industrial equipment in the field of animal protein, milk, cheese and wheat with self-sufficiency threshold (Alamdarlo et al., 2019, Soltani et al., 2020).
Nutritional status of Iranian population
Among countries, the variety of food consumption patterns is different and relies on cultures and social levels (Jessri et al., 2011). In recent decades, there have been considerable lifestyle modifications in Iran, especially in food consumption behaviors. Besides, several policies has been administered to improve nutrition statues and prevent malnutrition or obesity (Abdi et al., 2016, Baranowski et al., 2003, Legg et al., 2000). In 2005, a nationwide program was devised to reduce malnutrition in children under five years old. This program had two phases; first phase, was a collaborative phase, that covered all the mothers and their under six-year-old children in rural/urban health centers. The coverage included health planning, breastfeeding education, growth monitoring, illiteracy elimination, and also increasing access to food stores. The Second phase was a supportive phase focusing on low-income families who suffered from nutrition deficiencies and had growth-retarded or malnourished children. Previous studies have suggested that after ten years of administration, this program had some positive effects on children and reached an adequate extent; but, some aspects remained unclear, and there were some gaps that need more work (Ghodsi et al., 2018). Moreover, some vitamin and mineral deficiencies were prevalent in Iran including iodine, iron, zinc, vitamin B2 and vitamin A. In the case of vitamin B2, the most affected community were rural people, and non-standard food and dairy products were recognized as the most important factors (Ghassemi et al., 2002). A study in 2016 reported that in children under 5, there were 7.6%, 4.5% and 13.1% prevalence of underweight, wasted and stunted in Iran which were globally 16%, 8% and 26% (Abdi et al., 2016).
Food consumption
In Iran, the primary source of food production is agriculture, and due to several difficulties in marketing and production system it does not have an acceptable efficiency (Ardakani et al., 2017, Ardakani et al., 2009, Heslot, 2014). Moreover, about 35% of agricultural products, feeding 15 to 20 million people, are wasted and lost (Pirmoradi et al., 2013). To determine the changing trend in delivering food and nutrition security, an index for each dimension has been calculated by Ardakani et al. in five-year period, including accessibility, availability, stability and utilization; it has been indicated that in this period, accessibility and availability dimensions were steadily reduced (Table 1). Also, nutrition and food security in Iran from 2007 to 2011 sharply declined (Figure 2) (Ardakani et al., 2017). However, there have been great changes in Iranian dietary context and habits over time. The Iranian dietary pattern generally includes three categories of traditional, healthy, and western dietary patterns; the traditional dietary pattern is semi-healthy and mainly consists of rice, vegetables, red meat, fruits, soy, pickles, animal fat, and poultry. Healthy dietary pattern comprises fish, olive and vegetable oil, and little amounts of bread and animal fat; finally, western dietary patterns includes fast foods, soft drinks, sweets, cream, and high-fat meats (Zaribaf et al., 2019). Furthermore, Iranian food security has been affected by international sanctions, with greatest impact on the middle-class and poorer households. The sanctions caused great inflation in the price of food products; while people showed tendency to buy food products with lower price and less nutritional values (Heslot, 2014). Nowadays, the majority of population in Iran are not able to prepare foods with high nutritional quality, and they tend to buy cheap foods with high energy and less micronutrients, leading to more diet-related disease like obesity, type two diabetes mellitus (T2DM )and cardiovascular disorders (Pouraram et al., 2018).
Dietary changes
Besides nutrition transition, considerable dietary changes have also occurred, and fatty food consumption has increased. In traditional countries, fat consumption increased as well (Popkin, 1993, Umanath et al., 2016). Despite unhealthy food consumption, some lifestyle habits such as smoking and low physical activity contribute to adiposity and cardiovascular disease (CVD) (Sadeghi et al., 2017). Khatibi et al. demonstrated that high-fat and high-salt foods' led to the high prevalence of hypertension and CVD (Khatibi et al., 2018). Other studies showed that there was a higher prevalence of obesity in lower socio-economic levels of society, and also obesity increased through urbanization of big cities such as Tehran (Emamian et al., 2017). Based on the previous studies, people have more tendency toward fatty and fast foods (Mansouri-Tehrani et al., 2019, Mohammadbeigi et al., 2018, Rouhani-Tonekaboni et al., 2018). The prevalence of food insecurity among different groups in Iran is 49% in households, 49% in adolescents, 61% in mothers, 65% in the elderly, and 6% among children (Behzadifar et al., 2016, Shahraki et al., 2016). Traditional food patterns containing high amount of vegetable, wheat, and fruit is replaced with sugars and high fatty foods with less amounts of iron, iodine and other micronutrient deficiencies (Ardakani et al., 2017). Furthermore, 30% of households consume 80% of per capita energy- 3000 kcal per person- and this diet provides less than 80% of the essential micronutrients such as vitamin A, calcium, and riboflavin (Ghassemi, 2000, Rastegar, 2016).
Sedentary lifestyle and obesity
Obesity has a high prevalence worldwide, and a sedentary lifestyle is one of its main contributing factors, responsible for 5% of total deaths (Xie et al., 2014). A sedentary lifestyle is a health-related risk factor and leads to obesity and related co-morbidities (Smith et al., 2015). In Iran, evidence shows that obesity has been increased in recent years (Emamian et al., 2017), with a high prevalence in children and adolescents (Esmaili et al., 2015). Esmaili et al. in a nationwide study, demonstrated that the prevalence of overweight, obesity, and abdominal obesity among Iranian children and adults was higher in urban areas than in rural areas (Figure 3) (Esmaili et al., 2015). The cause of obesity is screen addiction including watching TV, cell phones, and tablets, and personal computers. Screen addiction such as TV watching is associated with lower metabolic rate in comparison with reading and writing which also sedentary activities (Hu et al., 2001, Sisson et al., 2012), and the risk of CVD increases by prolonged TV watching (Grøntved and Hu, 2011). Currently, the epidemiological transition in Iran led to nutritional problems among primary-school children and watching TV aggravated their food habits, which resulted in developing obesity independent of physical activity (Ghobadi et al., 2018). Also, according to a nationwide cross‐sectional survey, the leisure-time physical activity in men and women was 35.4% and 20.3%, respectively (Janghorbani et al., 2007). Iran is a developing country that has experienced urbanization, cultural, social, and economic transitions (Kelishadi et al., 2008). Over the past years, the prevalence of obesity among Iranian people significantly increased (Esteghamati et al., 2010). Interestingly, as described before, obesity in Iran for males and females was 3.34% and 3.50% in 2004 and 13.58% and 10.15% in 2012. However, the prevalence of abdominal obesity was 47.9% in 1999 and 71.1% in 2011 (Barzin et al., 2015, Djalalinia et al., 2016). Moreover, the prevalence of obesity has increased in children and adolescents (Djalalinia et al., 2016). The highest rates of obesity belonged to women of 40 and men of 20 ; higher waist circumference (WC) and lower education were also related to higher risk of obesity (Barzin et al., 2015). Sedentary behaviors and changes in diet could be the most important contributing factors to the increased prevalence.
Blood cholesterol and dyslipidemia
Dyslipidemia and high cholesterol levels in plasma are the most common problems leading to CVD. Dyslipidemia is defined with lower levels of high-density lipoprotein cholesterol (HDL-C), and higher values of triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and total cholesterol (TC) in the blood (Hedayatnia et al., 2020). Among the Iranian population, the prevalence of low HDL-C, hypertriglyceridemia, high levels of LDL-C, and hypercholesterolemia in both genders are 43.9, 46.0, 35.5, and 41.6 %, respectively (Hedayatnia et al., 2020). Recently, Hedayatnia et al. assessed the prevalence of dyslipidemia and related components among 8698 participants aged 35–65 with experience of heart attack in Mashahd (Table 2) (Hedayatnia et al., 2020). Moreover, it has been indicated that among Iranian adult patients with CVD, the prevalence of dyslipidemia was 87% (Darroudi et al., 2018, Hedayatnia et al., 2020). CVD is the major cause of mortality in Iran; among the cause-specific death rates, 79% of deaths are from chronic diseases, and 50% are related to CVD (Sadeghi et al., 2017). It has also been estimated that until 2025, CVD mortality will be increased (Figure 4); obesity, unhealthy diet, high-fat diet, and dyslipidemia are the most common causes of CVD (Després and Lemieux, 2006, Mathers and Loncar, 2006, Ordovas, 2006, Tveden-Nyborg et al., 2016). In a study on Iranian adults over 20 in 2019, it was demonstrated that from 1990 to 2011 the borderline increase in the blood cholesterol level in males was 39.8% and in females was 46.3% (Hosseini et al., 2019). Hosseini et al. reported that the prevalence of borderline increase in blood cholesterol nationwide had had an increasing
trend with the prevalence of 46.3%, while hypercholesterolemia’s prevalence rate was 18.0% in 1990-2011 (Hosseini et al., 2019). In the study conducted by Alimohammadi et al., the total cholesterol levels in females and males was reduced in the period of 1980 to 1990 and increased in 1990-2010; whereas, the figure for females had increased constantly from 1980 to 2010 (Alimohammadi et al., 2018).
Hypertension, T2DM and metabolic syndrome
Hypertension is one of the five global causes of mortality among children and adults, when obesity, hypertension, and other CVD risk factors are combined, the likelihood of adverse CVD significantly increases, and there is a need for aggressive treatment (Natsis et al., 2019). Based on the meta-analysis of 42 studies in Iran between 1980 and 2012, the total prevalence of hypertension was 22%, 23.6% in men and 23.5% in women. In addition, the prevalence of hypertension was higher in women ≥ 40 (Figure 5) (Mirzaei et al., 2016). In a study with 402,282 subjects, the prevalence of hypertension in urban and rural areas was 22.1% and 18.6% respectively (Mirzaei et al., 2016). Moreover, Mirzaei et al. showed that from 1980 to 2010, there was an increased prevalence of hypertension which increased with age; at the age range of over 40, the prevalence of hypertension in women was more than men (Mirzaei et al., 2016). It has also been indicated that Iranian people had higher daily consumption of salt compared with the National Training Program of United States guidelines, and people with lower socio-economic status had higher salt intake compared with people with higher socio-economic status (Mazloomy Mahmoodabad et al., 2016). There was a strong relationship between T2DM, and obesity, both of which are the most dangerous diseases among metabolic disorders (Verma and Hussain, 2017). In a study among 728 Iranian patients with T2DM, the relationship between obesity and dietary patterns was evaluated, and the results showed that there was a negative and positive association between healthy and unhealthy dietary habits, and the prevalence of general obesity (Basiri et al., 2015). Every year, T2DM imposes a huge financial burden on society and healthcare systems (Bakker et al., 2016). Previous studies demonstrated that there was a 35% increase in the prevalence of T2DM among the Iranian adult population between 2005 to 2011, contributing to the total prevalence of 11.4% (Esteghamati et al., 2014). Furthermore, Esteghamati et al. indicated that all kinds of diabetes showed a 85.5% prevalence of T2DM (Esteghamati et al., 2017). In a study in Tehran city, the prevalence of T2DM among people with low socio-economic status was higher than the other regions; they had a higher rate of T2DM (Asadi-Lari et al., 2016). Metabolic syndrome (MetS), is also a prominent disorder contributing to T2DM, hypertension, obesity, and dyslipidemia. A nationwide survey showed that the prevalence of MetS among the urban population, older adults, low educated people, postmenopausal women, and people with unhealthy diets and low physical activity was higher than the other groups (Hajian-Tilaki, 2015). Since one of the significant factors of MetS is obesity, and obesity directly relates to lifestyle, some studies revealed that the rate of obesity among Iranian adults has increased in the last decades (Azimi-Nezhad et al., 2012, Hajian-Tilaki and Heidari, 2007, Jouyandeh et al., 2013, Shahini et al., 2013); this rate was almost higher in women (Azimi-Nezhad et al., 2012, Delavari
et al., 2009).