Dietary diversity score (DDS) is defined as a number of individual food groups consumed over a given period of time [1]. It reflects quality diet at the household or individual level. In addition, DDS is measure of food security, nutrition information, early warning system and target of intervention at Global or national level [2, 3]. Mostly, monotonous staple diets lack essential micronutrients which lead to macro and micronutrient deficiencies, particularly in the most vulnerable group [4, 5].

Optimal nutrition is critical during adolescence as 50, 20 and 50% of adult weight, height, and skeletal mass are gained in this period [6–8]. However, 45–60% of adolescent girls are found with sub-optimal dietary intake [9] resulting in development of varied micronutrient deficiencies (Vitamin A, iron and iodine deficiencies) [5, 8, 10–12]. Similar finding showed in Ethiopian 29 and 30% of adolescent girls had thinness and anemia, respectively [13]. Furthermore, delayed puberty, contracted pelvis and unfavorable birth outcomes are noted in undernourished adolescent girls [14, 15].

Globally, Only 17% of adolescents had diversified diet [16]. Similarly, 23.5–50% [17, 18] of the Iranian, 11.2% of Zimbabwe [19] and 26.8% [4] Ethiopian Adolescents were reported as having adequate dietary diversity. Number of the researches documented that maternal education [4, 20], school type [20], occupation [20], nutritional knowledge [21], household food security [22], residence [4, 22] and wealth status [4, 20, 22] were associated with dietary diversity of adolescents. Considering the burden of sub-optimal dietary intake, promotion of adequate dietary diversity becomes one of the global concerns [23]. However, the level of adolescent’s dietary diversity is not well investigated in Ethiopia [4]. Therefore, this study assessed dietary diversity and associated factors among school adolescent girls in Gondar City Administration.

A school-based quantitative cross-sectional study was conducted from March to April 2017 in Gondar City Administration; northwest Ethiopia. The City has 42 primary and 14 secondary and preparatory schools. All adolescent girls attending both private and governmental schools during the study period were considered as a source population.

A single population proportion formula was used to estimate sample size. Assumptions considered in sample size calculation were 26.8% as prevalence of adequate dietary diversity among adolescent high school girls in Gurage Zone [4], 95% confidence level, 1.5 design effect, 10% non-response rate and 4% degree of precision. Finally, a sample size of 778 was obtained. Schools were stratified into private and governmental schools and then ten schools were selected by lottery method. Simple random sampling technique was employed to choose samples using complete list of students as a sampling frame. Participants included in the study were proportional to the total students enrolled in private and governmental schools.

Concerning the data collection activity, interviewed based questionnaire was used to collect data. The tool was developed by reviewing different literatures, food and Agriculture Organization (FAO); FHI 360. Minimum Dietary Diversity for Women and health survey reports. Primarily the tool was prepared in English and translated to Amharic, the local language, and re-translated to English to check consistency of the questionnaire. Four data collectors (clinical nurses) and two BSc nurses as a supervisor were trained prior to data collection. The questionnaire was pretested among 39 school adolescent girls out of the study area. The training majorly encompasses dietary intake measurement and questionnaire administration techniques and ethical issues of the study.

The outcome, dietary diversity, was assessed using a standard tool suggested by Food and Agricultural Organization to measure women’s dietary diversity. Food consumed by adolescents was assessed through 24-h recall method and then food items were categorized into ten food groups. Dietary Diversity Score (DDS) was created as a summary measure of dietary intake, accordingly participants who had DDS of five and above were deemed as having adequate dietary diversity, whereas inadequate DDS was ascertained when they had less than five DDS [24].

EPI INFO version 3.5.3 and SPSS version 20 were used for data entry and analysis, respectively. A binary logistic regression model was fitted to show the effect of exposure variables on dietary diversity. A variable screening criteria of P-value less than 0.2 was used in the bivariate analysis to select candidate variables for the final model, multi-variable logistic regression analysis. In the adjusted analysis, independent variables with a P-value of < 0.05 were considered as independent factors associated with Dietary Diversity. Model fitness was checked using Hosmer-Lemeshow goodness of the fit test.

This study illustrated that three-fourth (75.4%) of adolescent girls had diversified diet. The finding was higher than the reports of developing countries, including Iran (26.55%) [25], Zimbabwe (11.2%) [26], Adama City (41.2%) [27], Gurage Zone (26.8%) [4], Amhara region (21.8%) [28]. The high prevalence of adequate dietary diversity in this study area could be due to the nature of the study. Almost all (93.4%) of adolescent girls were included from the urban kebeles and enrolled in schools. Such source of discrepancies could explain increased proportion of diversified diet. In addition, do not have information about better dietary intake habits [20]. However, the result was slightly lower than the study conducted in Agarfa, Ethiopia (80.4%) [29]. This study used five food groups as cut-off point to determine adequate diversity, whereas the previous study considered four food groups. Use of low cut-off might inflate the prevalence of diversified diet in the former study. Obviously, dietary habit of developing nations is entirely depends on starchy staples [30]. This study also confirmed that almost all (97.7%) of participants consumed grains, root and tubers. This result was supported with the previous local report [4].

The result of multivariate logistic regression analysis showed that adolescent girls from private schools had higher odds of diversified diet compared to those who attended governmental schools. In Ethiopia context, students enrolled in private schools are majorly from better-off families hence, poor families usually do not afford monthly school fee. High household socio-economic status is key to enhance household and individual dietary diversity [25, 31, 32]. Adolescents living in better-off households could have improved nutrition information access because of better availability of media source [33].

Lastly, the odds of diversified diet were high in adolescent who lived in urban areas compared to those who lived in rural areas. This finding was supported by researches elsewhere [4, 23, 34, 35] conduct in, China children [36], Mali [34], Gurage [4] and Jimma Zone [22]. In fact, food security, socio-economic status and access to variety of food and information are higher in the urban settlements than the rural areas [22, 35, 37, 38]. This might explain the observed difference in dietary diversity with place of residence. The study attempted to show dietary diversity in the most vulnerable group of the population representing the rural northwest Ethiopia, but, some of the limitations of this study should be taken into consideration. First, the study did not consider the quantity of food consumed by the adolescent and single 24 h recall did not indicate the usual dietary habit of the adolescent. There might be social desirability bias in responding type food given to children and recall bias.

In summary, the prevalence of adequate dietary diversity is high in Gondar City Administration. Type of school and place of residence were significantly associated with adolescent’s dietary diversity. Hence, efforts focusing to improve dietary diversity should give special attention to government schools and the rural adolescents.