Results

Based on the systematic search (Fig. 1), we retrieved 238 articles from Web of Science and 542 from PubMed search engines. In Google Scholar, the first 200 results were considered. Supplementary Table S1 outlines the search strategy and strings used for each database. Based on the bibliographic searches, 980 records were retrieved in total. Following deduplication and merging 837 studies were left. 302 studies were excluded after title and abstract screening, leaving 535 records for full-text screening. Of those, 446 studies were excluded for various reasons. Eventually, 89 studies were included for qualitative synthesis. In addition, 34 studies were found after screening the reference lists of the 89 studies included in the qualitative synthesis. Of these 34 records, only 13 studies were eligible to be added to the previous 89 studies, bringing the number of studies contributing to the systematic review to 102 records.

Fig. 2. Summary of the individual studies reporting anthropometric indicators over time.

Table 1 shows the characteristics of included studies. A total of 102 cross-sectional studies have been examined and reported. Sample sizes ranged from as small as 22 to as large as 7,625. Approximately half of the study sites, representing (n = 51), were located in the south-western region of the country. Conversely, the north western region was the least represented with merely 3.9% of the studies conducted there (4 out of 102 studies). A visual map with study locations and population density of all included studies is available in supplementary Fig. S1. The majority of studies (86%) included both male and female participants. Educational institutions were predominantly utilised as the research setting in over 70% (77 out of 102) of the studies. Substantial heterogeneity was observed with regards to the methodological approach to dietary assessment and anthropometric classification tools adopted in these studies. Questionnaires were the most widely employed data collection instrument, featured in nearly 81 out of 102 studies. Based on the JBI tool evaluation, 13 studies were classified as ‘low risk of bias’, representing 12.7% of the total 102 studies. Conversely, 46 studies, accounting for 45.1%, were assessed as having ‘some concerns’ for bias, while 43 studies, or 42.2%, were rated as at ‘high risk of bias’. The most commonly used dietary assessment tool was a questionnaire. Other tools included the 24-hour dietary recall, food frequency questionnaire, and diet diversity score. The administration method was predominantly self-administered or researcher-administered. Validation: There was a mixed validation status for the instruments used. While many of the questionnaires were not validated, a minority of studies used validated tools. Most of studies (84.3% or 86/102) were published in journals that were not indexed and consequently had no impact factor at the time of publication.

Table 1. Study characteristics of the studies included in the systematic review

Note: ♀, Male; ♂, Female; NR, Not Reported.

Table 2 provides a summary of anthropometric findings of nutritional epidemiology studies conducted in Nigeria among adolescents. Out of the total, sixty-six studies documented either primary or composite anthropometric measures or a combination thereof. Composite anthropometric measures encompassed various indicators such as underweight, overweight, stunting, obesity, thinness and wasting. Of note, 77.2% of the studies reported different manifestations of undernutrition, such as stunting, wasting and/or underweight. Furthermore, 68.2% of the studies indicated the prevalence of overweight and obesity, which constitute forms of over nutrition. Additionally, the height-for-age z-score (HAZ) and weight-for-age z-score (WAZ) were reported in about 39% of the studies (25 out of 66). The overall range for body mass Index (BMI, in kg/m²) across all studies that reported it, ranged from 15.7 to 24.6. Height (in metres) varied within a range of 1.2–1.7 and weight (in kilograms) ranged from 19 to 70. With regard to the prevalence of simple nutritional status phenotypes (expressed as percentages), the overall range was as follows: underweight from 2.5% to 78.3%; overweight from 1.4% to 25.2%; stunting from 2.5% to 77.1%; wasting from 1.7% to 56%; and obesity from 0.2% to 21%.

Table 2. Anthropometric findings from Nigerian nutritional epidemiology studies

Note: Values are given in percentage unless otherwise indicated.

Table 3 presents findings on food and food group consumption for Nigerian adolescents, from 29 nutritional epidemiology studies that reported consumption data for at least one food and/or food group.^{(Reference Afolabi, Towobola and Oguntona25–Reference Agoreyo and Obuekwe27,Reference Akinola, Odugbemi and Bakare31,Reference Ayogu38–Reference Bamidele, Oyenike and Olusegun40,Reference Funke and Ajayi56,Reference Ikujenlola and Adekoya60,Reference Ogunkunle and Oludele70,Reference Ogunsile71,Reference Okoro, Ogunbiyi and George74,Reference Olatona, Onabanjo and Ugbaja76,Reference Olatona, Ogide and Abikoye77,Reference Olumakaiye, Atinmo and Olubayo-Fatiregun80,Reference Onyiriuka, Ibeawuchi and Onyiriuka94–Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Otemuyiwa and Adewusi101,Reference Otuneye, Ahmed and Abdulkarim102,Reference Samuel, Adenekan and Adeoye104,Reference Sanusi, Wang and Ariyo105,Reference Sholeye, Animasahun and Salako110,Reference Uba, Islam and Haque113,Reference Orisa and Wordu117–Reference Ansa, Anah and Ndifon120)} Starchy staples, encompassing cereals and starchy roots/tubers, emerged as a commonly consumed dietary component, were reported by eleven studies and consumption levels ranged from 28.2% to 96.7%.^{(Reference Afolabi, Towobola and Oguntona25,Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Ayogu38,Reference Ogunkunle and Oludele70,Reference Okoro, Ogunbiyi and George74,Reference Olatona, Onabanjo and Ugbaja76,Reference Olatona, Ogide and Abikoye77,Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Otemuyiwa and Adewusi101,Reference Uba, Islam and Haque113,Reference Orisa and Wordu117)} However, only two studies reported consumption levels below 50%.^{(Reference Afolabi, Towobola and Oguntona25,Reference Olatona, Onabanjo and Ugbaja76)} Legumes, nuts, and seeds were reported in six studies.^{(Reference Afolabi, Towobola and Oguntona25,Reference Ayogu38,Reference Ikujenlola and Adekoya60,Reference Ogunkunle and Oludele70,Reference Sanusi, Wang and Ariyo105,Reference Orisa and Wordu117)} Similarly, consumption of meat, poultry, fish, and seafood ranged from 19.1% to 62.1%, reported in nine studies.^{(Reference Afolabi, Towobola and Oguntona25,Reference Ayogu38,Reference Ikujenlola and Adekoya60,Reference Ogunkunle and Oludele70,Reference Okoro, Ogunbiyi and George74,Reference Olatona, Onabanjo and Ugbaja76,Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Otemuyiwa and Adewusi101,Reference Orisa and Wordu117)} Vegetable consumption was documented across eleven studies with a range from 10.1% to 83.0%, with seven studies indicating proportions below 50%.^{(Reference Afolabi, Towobola and Oguntona25,Reference Ayogu38–Reference Bamidele, Oyenike and Olusegun40,Reference Ogunkunle and Oludele70,Reference Ogunsile71,Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Uba, Islam and Haque113,Reference Orisa and Wordu117–Reference Oroniran, Olawuyi and Fadupin119)} Fruit intake ranged from 9.7% to 77.4% and was reported across seventeen studies.^{(Reference Afolabi, Towobola and Oguntona25,Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Akinola, Odugbemi and Bakare31,Reference Ayogu38,Reference Bamidele, Oyenike and Olusegun40,Reference Ikujenlola and Adekoya60,Reference Ogunkunle and Oludele70,Reference Ogunsile71,Reference Okoro, Ogunbiyi and George74,Reference Olatona, Ogide and Abikoye77,Reference Onyiriuka, Ibeawuchi and Onyiriuka94,Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Otemuyiwa and Adewusi101,Reference Sanusi, Wang and Ariyo105,Reference Orisa and Wordu117–Reference Oroniran, Olawuyi and Fadupin119)} Conversely, sweets’ consumption was described in six studies^{(Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Ogunsile71,Reference Okoro, Ogunbiyi and George74,Reference Onyiriuka, Ibeawuchi and Onyiriuka94–Reference Onyiriuka, Umoru and Ibeawuchi96)} showing variation across the studies (range: 35.3–62.4%). Snacking habits were recorded and reported in ten studies (range: 33–96.8%).^{(Reference Funke and Ajayi56,Reference Ikujenlola and Adekoya60,Reference Ogunkunle and Oludele70,Reference Olatona, Onabanjo and Ugbaja76,Reference Olatona, Ogide and Abikoye77,Reference Olumakaiye, Atinmo and Olubayo-Fatiregun80,Reference Onyechi and Okolo93,Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Samuel, Adenekan and Adeoye104,Reference Orisa and Wordu117)} Additionally, consumption of sugar-sweetened beverages was indicated in 13 studies.^{(Reference Agoreyo and Obuekwe27,Reference Akinola, Odugbemi and Bakare31,Reference Bamidele, Oyenike and Olusegun40,Reference Ogunsile71,Reference Olatona, Onabanjo and Ugbaja76,Reference Onyiriuka, Ibeawuchi and Onyiriuka94–Reference Onyiriuka, Umoru and Ibeawuchi96,Reference Otuneye, Ahmed and Abdulkarim102,Reference Sholeye, Animasahun and Salako110,Reference Orisa and Wordu117,Reference Oroniran, Olawuyi and Fadupin119,Reference Ansa, Anah and Ndifon120)} Consumption of such beverages exhibited a wide spectrum, ranging from 8.5% to 99.4%. Only two studies reported egg consumption (range: 3.3–14.3%).^{(Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Ayogu38)}

Table 3. Food and food group-based findings

^a Values are provided in percentage (%), unless otherwise indicated.

Table 4 summarises dietary intake among adolescents in Nigeria. Results show that the amount of protein (range: 27–93.5 g), energy (range: 903–5754.7 kcal) and carbohydrate (range: 82–937.60 g) consumed by majority of adolescents were inadequate^{(Reference Ayogu38,Reference Ene-Obong, Doh and Ikwuagwu46,Reference Ogechi, Akhakhia and Ugwunna68–Reference Ogunkunle and Oludele70)} also one study reported an inadequate consumption of fat (range: 6.0–157.1 g) by this age group.^{(Reference Ogunkunle and Oludele70)} In contrast, some studies reported an excessive intake of carbohydrate, energy and protein beyond recommended nutrient intake.^{(Reference Ogunkunle and Oludele70,Reference Olumuyiwa, Israel and Oluwemimo82,Reference Shokunbi and Ukangwa109,Reference Tassy, Eldridge and Sanusi112)} Only two studies^{(Reference Akinlade, Afolabi and Oguntona30,Reference Yunusa, Ahmad and Gidado116)} reported on fibre intake (range: 13.1–33.1 g) among Nigerian adolescents. One of the studies showed an intake of fibre less than 20 g (when defined as no starch polysaccharide) from foods—or less than 25 g from foods (when defined as total dietary fibre)—which are also the accepted values recommended for the prevention of NCDs.⁽¹²²⁾ With regards to vitamin intake, the most commonly reported vitamins in the studies included in this systematic review are vitamin A (range: 132.4–9135.2 mg), vitamin C (range: 7.2–80.8 mg), vitamin B₁₂ (range: 0–1.4 mg) and folate (range: 0–136.6 mg). Virtually all studies reporting them found insufficient consumption of these vitamins among adolescents.^{(Reference Akinlade, Afolabi and Oguntona30,Reference Akinyemi and Ibraheem32,Reference Ene-Obong, Doh and Ikwuagwu46)} Information gathered also shows an inadequate intake of minerals and trace elements, particularly calcium, iron, zinc and potassium. There was a report of excessive sodium intake (2225–2404 mg compared to the recommended value of 1200–1500 mg).^{(Reference Shokunbi and Ukangwa109)}

Table 4. Dietary intake by adolescents in Nigeria

Note: RNI, Recommended Nutrient Intake; NR, Not reported; RDA, Recommended Dietary Allowance; PUFA, Polyunsaturated fatty acids; FFQ, Food Frequency Questionnaire; DDS, Dietary Diversity Score.

Table 5 presents a summary of dietary habits among Nigerian adolescents. The studies included in the table report findings related to key dietary characteristics such as the number of meals, observing breakfast, eating lunch, eating dinner, and skipping meals. Specifically, the table includes findings from twenty-one studies.^{(Reference Adebimpe17,Reference Afolabi, Towobola and Oguntona25,Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Akinola, Odugbemi and Bakare31,Reference Essien, Emebu and Iseh51,Reference Ikujenlola and Adekoya60,Reference Iyalomhe, Iyalomhe and Nwadike61,Reference Ogunkunle and Oludele70,Reference Ogunsile71,Reference Olatona, Onabanjo and Ugbaja76,Reference Olumakaiye, Atinmo and Olubayo-Fatiregun80,Reference Omuemu and Oko-Oboh86,Reference Onyiriuka, Ibeawuchi and Onyiriuka94,Reference Onyiriuka, Egbagbe and Onyiriuka95,Reference Otuneye, Ahmed and Abdulkarim102,Reference Samuel, Adenekan and Adeoye104,Reference Sanusi, Wang and Ariyo105,Reference Uba, Islam and Haque113,Reference Orisa and Wordu117,Reference Onyechi and Okolo118,Reference Olatona, Oloruntola and Adeniyi123)} Among these studies, nine^{(Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Ikujenlola and Adekoya60,Reference Iyalomhe, Iyalomhe and Nwadike61,Reference Ogunsile71,Reference Olatona, Onabanjo and Ugbaja76,Reference Olumakaiye, Atinmo and Olubayo-Fatiregun80,Reference Omuemu and Oko-Oboh86,Reference Sanusi, Wang and Ariyo105,Reference Orisa and Wordu117)} reported the number of meals based on a three-square meal basis. Thirteen^{(Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Akinola, Odugbemi and Bakare31,Reference Ikujenlola and Adekoya60,Reference Ogunkunle and Oludele70,Reference Ogunsile71,Reference Otuneye, Ahmed and Abdulkarim102,Reference Sanusi, Wang and Ariyo105,Reference Onyechi and Okolo118)} studies provided information on the proportion of participants who observe breakfast, while seven^{(Reference Ogunkunle and Oludele70,Reference Omuemu and Oko-Oboh86,Reference Onyiriuka, Ibeawuchi and Onyiriuka94,Reference Otuneye, Ahmed and Abdulkarim102,Reference Sanusi, Wang and Ariyo105,Reference Uba, Islam and Haque113,Reference Onyechi and Okolo118)} studies reported the proportion of participants who observed lunch meal. Only one^{(Reference Otuneye, Ahmed and Abdulkarim102)} study reported the responses of participants regarding the order of importance of meals, fasting to lose weight, using diet pills to lose weight, infrequent intake of fruits/vegetables, consuming alcohol and smoking cigarettes. Furthermore, eight^{(Reference Adebimpe17,Reference Afolabi, Towobola and Oguntona25,Reference Essien, Emebu and Iseh51,Reference Ikujenlola and Adekoya60,Reference Olatona, Onabanjo and Ugbaja76,Reference Onyiriuka, Ibeawuchi and Onyiriuka94,Reference Samuel, Adenekan and Adeoye104,Reference Orisa and Wordu117)} studies examined fast-food consumption, and four^{(Reference Agofure, Odjimogho and Okandeji-Barry26,Reference Iyalomhe, Iyalomhe and Nwadike61,Reference Onyiriuka, Egbagbe and Onyiriuka95,Reference Otuneye, Ahmed and Abdulkarim102)} studies investigated factors that motivate dietary intake.

Table 5. Findings on dietary habits of the available studies

Table 5 provides information on studies reporting dietary habits of Nigerian adolescents. With regards to meal patterns the proportion of participants reporting consuming three-square meals varied across studies, ranging from 33% to 85%. A majority of participants generally observed breakfast, with proportions ranging from 16.4% to 95%. Lunch and dinner were also commonly consumed meals, with proportions ranging from 6.9% to 95.5%. Skipping meals was prevalent among adolescents, with proportions ranging from 10% to 86%. Breakfast skipping was particularly common, reported by 48% to 86% of participants in different studies. Fast food consumption was widespread among adolescents, with proportions ranging from 16.5% to 87.8%. Some studies highlighted a higher prevalence of fast-food consumption among females. Fruit consumption varied across studies, with proportions ranging from 48.3% to not been reported. The frequency of fruit consumption was generally moderate, with a significant proportion reporting eating fruit sometimes.

Fig. 2 shows a summary of results from studies reporting anthropometric indicators and these studies have been ordered by year, to provide a trend over time. For all 5 indicators (obesity, stunting, thinness, underweight and wasting) the trends appear to decrease over time.