To our knowledge, this study is one of the first to provide evidence on a nationwide prevalence and factors associated with underweight among 15–49-year-old women of reproductive age in Sierra Leone (Tables 1, 2, Figs. 1, 2 and Table 3). To ensure optimum generalizability of our findings, we used a nationally representative data from the Sierra Leone Demographic Health Survey of 2019 (2019-SLDHS)  (Fig. 1). Specifically, this study determined the prevalence of underweight among women of reproductive age (15–49 years) in Sierra Leone at 6.7% (502/7,514) (Table 1).
The prevalence of underweight at 6.7% is within a range comparable to many countries in sub-Saharan Africa [39,40,41,42]. This prevalence is lower compared to studies conducted in Kenya (9%)  and Tanzania (10%)  but like that of Nigeria (6.7%) . The underweight prevalence is also within the range of 5 to 20% reported among women (15–49 years) in the African continent .
In a study by Senbanjo et al., from one state of Lagos in Nigeria for example , only women aged 15–39 years were included in the survey while the other two studies from Tanzania  and Kenya  included women aged 15–49 years like our current study. In addition, a World Food Program (WFP) study on East African Regional Food Security & Nutrition update found that Uganda has the lowest prevalence of undernutrition in the East African region partly because of better food security among most of its population compared to Djibouti, Somalia, South Sudan, Burundi, and Kenya .
Also, equated with Asian countries and globally, this Sierra Leonean’s underweight prevalence is lower compared to Indonesia at 11.2% , Bangladesh at 16.5%  and globally at 10% . The observed differences in underweight prevalence among women of reproductive age in the five countries (Uganda, Kenya, Tanzania, Nigeria, and Sierra Leone) which are all in sub-Saharan Africa is likely due to differences in characteristics of study participants, country of origin, age-groups, and their food security status.
The odds of being underweight was significant among participants aged 15–24 years and this was two and a half times more likely than those aged 25–34 years (Table 5). This finding is consistent with other studies in India and other sub-Saharan African countries [44,45,46]. The current finding in Sierra Leone is likely because this age-group (15–24 years) which consists mainly of adolescents experience rapid physical growth, psychosocial, and cognitive development which requires sufficient nutrient intake to cope with the demand of growth and development. This age-group requires an increased need for nutrients which were likely insufficient in the Sierra Leone’s situation . In addition, a similar high underweight prevalence was observed among adolescent girls in south Asia where over 50% of adolescent girls were affected by undernutrition and anemia due to unmet nutrient requirement, inadequate food supply, and intake . Likewise, the prevalence of underweight was reported high among adolescents living in many countries in sub-Saharan Africa, particularly in Ethiopia [49, 50]. This current Sierra Leone’s report on underweight is likely due to household poverty (Table 1) and food insecurity resulting from lack of food available for consumption because diet and dietary habits are the main factors for underweight in adolescents [51,52,53]. This is supported by a finding in our study that most underweight 345/502(68.7%) women (15–49 years) in this study population, were in households classified in the poorest, poorer, and middle wealth indices (Tables 1 and 2). In addition, most underweight women 289/502(57.6%) were in the 15–24-year age-group (Fig. 2).
Our study also found that most participants 3,571(47.5%) had no formal education (Tables 1, 3 and 4). As most participants hailed from rural areas 4,422(58.9%), we ascertained that the proportion of participants with no formal education was lower among the urban compared to rural participants (Table 4). We found the actual proportion of participants without formal education was at 39.2% in urban compared to 61.1% in rural areas (Tables 3 and 4). We found that most participants in this survey were aged 15–24-years, 2916/7514(38.8%) and this age-group had a higher proportion of formally educated underweight participants at 231/291(79.4%) compared to their older counterparts at 20/291(6.9%) (Tables 1, 3 and 4). The overall number of underweight women without formal education were more in the older age-group (35–49 years) 109/211(51.7%) compared to 20/291(6.9%) among educated participants in the same age-group (Tables 3 and 4).
Even though most underweight women had formal education 291/502(58.0%), its prevalence among women without formal education was lower at 211/502(42.0%). The majority of those who had no formal education were in the age-group of 35–49 years 109/211(51.7%) (Table 4). Lastly, it is important to note that underweight among women (15–49 years) was not significantly associated with the level of education or residence (rural versus urban) of participants in this study population (Tables 3, 4 and 5).
Our study also found that not married women were unlikely of being underweight than married women (Table 5). In contrast to a previous study in Bangladesh in a pooled analysis, it found that not being married was positively associated with underweight . As well, two previous studies in Ethiopia and Iran are inconsistent with our study where not married were more likely of being underweight compared to married women [55, 56].
Many reports from developing countries show that being married provides women with more excellent financial stability, which in turn works as a protective factor from being underweight [57, 58]. Other factors, such as the use of contraceptive pills, and weight gain in the postpartum period, are more likely to be prevalent among married women in many countries’ contexts [57, 58]. One study in Ethiopia showed that women’s nutritional status is affected by lactation, family planning method utilization, lack of education, illnesses, and poor dietary habits . Of note, our current study excluded pregnant, post-natal, and postpartum women, perhaps explaining the inconsistent findings of our study compared to other studies from the African continent.
So, the hypothesis that married women get protected from being underweight because of social shields should be explained in the context of countries, regions, and continents. There is a need for proper and factual explanation on the plausible hypothesis on social protection of married women from being underweight. This warrants a deeper exploration of the socio-cultural dynamics of Sierra Leone communities because our current findings are in contrast with trending information and what has been seen in Ethiopia and Iran [55, 56]. As expected, further studies will be required to establish or disprove any plausible causal connections between not married and not being underweight.
Of special interest from our study was that parity of one to four was one and half times more likely of being underweight compared to women who never gave birth (Table 5). This additional information provides important direction for further enquiry, the negative effect of parity of one to four children on underweight among women (15–49 years) in Sierra Leone (Table 5). This finding in Sierra Leone on parity is consistent with studies in Maldives , Burundi, and Ethiopia , where higher parity of more than two children were negatively associated with underweight among women of reproductive age. Experts suggest that parity as a risk factor of underweight in women of child-bearing age could reflect multiple reproductive cycles within short intervals which does not allow for sufficient replenishment of women body’s nutrient stock . They argue that women are physiologically vulnerable to malnutrition especially with reproductive functions such as pregnancies and breastfeeding often increasing nutritional requirements [62, 63]. Again, it is said that women in poverty-stricken settings where food insecurity is endemic are often engaged in energy demanding agricultural occupations that often leaves them nutritionally depleted . Endemic household food insecurity provides a reasonable explanation for parity of one to four as a risk factor for underweight among Sierra Leone’s women in reproductive age.
Also, our study found that it was unlikely of being underweight among residents of northern Sierra Leone compared to the east although, there was no significant associations between underweight and northwestern, western, and southern regions of Sierra Leone compared to the east (Table 5). Previous studies showed that regions of residence were associated with underweight in similar low-income African settings [39, 64, 65] and Afghanistan . Similar DHS studies in Uganda found a high prevalence of underweight among women (15–49 years) residents of northeastern region of Uganda who are the poorest and most food insecure [67, 68]. Finding in northeastern Uganda was likely because the region suffers frequent prolonged annual droughts and long civil unrests which significantly affect agricultural production and economy compared to other parts of the country without civil conflicts . In this, experts suggest that decreased agricultural production and poor economy in northeastern Uganda was mainly due to prolonged annual droughts and civil war-induced food insecurity [68,69,70]. Further, it was proposed that reduction in food production coupled with decreased availability and access of food to the population was common in that region [68,69,70] and leads to inadequate food in quality and quantity, risking the population from being underweight .
Too, most population in northeastern region unlike other regions of Uganda are pastoralists/nomads, and this affect their consumption of food crops as they focus mainly on rearing livestock and move from one location to another frequently . Of note, pastoralists/nomads in Ethiopian pastoral communities, like some communities in East African countries have increased risks of being underweight .
In this, a previous report from Sierra Leone showed that nearly half a million children under five years suffer from stunting, while 30,000 suffer from malnutrition and were at immediate risk of death due to inadequate dietary intake, poverty, and high burden of diseases . Some experts argue that there are four primary factors contributing to Sierra Leone’s overwhelming poverty: corruption, not a well-established educational system, absence of civil right activities, and poor infrastructures . They argue that these four factors make poverty challenging to beat in Sierra Leone as they have become systemic problems .
However, we the authors argue that researchers should not under look the uniqueness of the characteristics of the population in northern Sierra Leone . The culture, tribes, social networks, religious practices, marital arrangements, socioeconomic activities, environment, household wealth indices, social dynamics, and family support systems of the population in northern Sierra Leone which are exclusive may in part explain their unlikeliness of being underweight compared to eastern region .
We, the authors propose that additional studies are warranted to determine why underweight is unlikely in northern Sierra Leone compared to eastern region as this current finding presents a unique scenario in a country afflicted by similar challenges but have different effects on northern region compared to other regions (Tables 2 and 5).
Listening to radios
Our study found that not listening to radios was protective against being underweight among women of reproductive age (15–49 years) in Sierra Leone (Table 5). This is in contrast with a study in Botswana which found that approximately 12.9% of women who did not listen to radios the previous week compared to 11.1% who did, had a low BMI or were underweight . Overall, a higher proportion of women who never listened to radios at least once a week had a higher prevalence of underweight compared to those who did . This finding is inconsistent with our current study in Sierra Leone where not listening to radios was protective of being underweight (Table 5). In addition, findings from Botswana show that young adult women who lacked access to mass media were at greater risks of underweight .
As previously observed, radios are vital sources of information on various issues such as health communications and promotion . Through radios, people receive and learn messages about healthy eating behaviors and lifestyles . Thus, it was assumed that those who owned radios were expected to be better informed about food, diet, healthy lifestyles and were able to learn and adopt healthier lifestyle .
The assumption in the Botswana study was that participants without a radio did not know about healthy eating behaviors and lifestyles or they could not have access to information on healthy eating behaviors from other sources other than radios and were more likely of being underweight .
Interestingly, there are other sources of information to women in the reproductive age in African communities other than radios for example, from health workers, midwives, elders, friends, family members, social networks, traditional leaders, older women, mosques, churches, internet, mobile phones, social media, and others that allow women to get information. Whether these additional sources of reproductive health information to women were considered important issues, or ignored, or not included in the options in the study questionnaire will be one of our future areas of enquiry in Sierra Leone.
In addition, many African communities live in villages, gather in village clubs in the evening for socialization, for example, while drinking alcohol whereby news and updates from radios or mobile phones are shared with neighbors but the ownership remains for a person. These extra scenarios that may not have been captured in this study; a self-administered questionnaire using computer-assisted personal interviewing (CAPI) for quantitative data collection attract interests of qualitative researchers to explore more about health information and communications among the study population.
We, the authors posit that the culture, feeding habits, social networks and dynamics, food availability, and economic activities of women in northern Sierra Leone are likely different from Botswana, Uganda, and Ethiopia, and not listening to radios was protective of being underweight.
As observed in our findings, young women (15–24-year age-group) were the most significantly affected by underweight compared to the older age-groups (Table 2, Fig. 2, Tables 3, 4 and 5). For this significant association between underweight and women of 15–24-year age-group, we, the authors propose that introducing school feeding programs in Sierra Leone’s schools is important for mitigating underweight challenges observed among young women in the reproductive age (15–49 years) in schools.
Findings from our study are very important as a special report on Sierra Leone about the status of teenage pregnancy in 2020 shows it is on the rise [67, 73]. MEDICI CON L’AFRICA, CUAMM, Doctors with Africa says that teenage pregnancy is a big problem affecting girls’ and young women’s health, their social, economic, and political empowerment in Sierra Leone . Overall, the report shows that 28% of adolescent girls aged 15–19 years had begun childbearing; 22% have had a live birth, and 6% were pregnant with their first child as of the date of the survey . In addition, a larger proportion of teenagers in rural areas than in urban areas had begun childbearing (34% versus 19%)  while at regional level, the proportion of teenagers who had started childbearing was highest in the Southern region (33%) and lowest in the western region (18%) . This report therefore highlights the urgent need for practical interventions to curb underweight among women of reproductive age in Sierra Leone especially among the teenagers and young adolescents.
Overall, our study found that age-group of 15–24-years and parity of one to four were significantly associated with being underweight. Not listening to radios, residents from the northern region and not married were protective factors against underweight among women (15–49 years) in Sierra Leone (Table 5). However, residency (rural versus urban), sex of the head of household, household size, work status, level of education, wealth indices, reading magazines, watching television, smoking cigarettes, and alcohol use were not significant factors of underweight among women of reproductive age (15–49 years) in Sierra Leone (Table 5). Findings from our study in Sierra Leone show a lower prevalence of underweight compared to Indonesia  and Ghana , even though they are all in low-to-middle-income countries.
Strengths of this study
This study has many strengths. First, this study utilized a nationally representative sample population of women in the reproductive age (15–49 years) in Sierra Leone. Second, the data quality was assured as the 2019 SLDHS used well-trained field personnels, standardized protocols, and validated tools in data collection processes. In addition, a group of well trained and experienced scientists collected, cleaned, and entered the data with minimal errors in the final dataset. As a result, findings of this study can be generalized to the target population in Sierra Leone and other developing countries. Third, because we used validated tools and calibrated instruments by SLDHS, the generated estimates are more robust than other studies in the context of Sierra Leone. Finally, we used concentration index whose findings are more robust in predicting socio-economic inequalities in a study population.
There are some limitations in this study which warrants further discussions. First, the 2019 SLDHS was a cross-sectional survey conducted among women of reproductive age (15–49 years). As a result, we cannot establish causal associations between explanatory variables and the outcome variable.
Second, due to the absence of some data, several important variables such as food security and dietary diversity were not part of the model in the final analysis. Third, SLDHS did not collect individual household income and expenditures data. The survey used household wealth index as a proxy indicator for household wealth measures which offers limitations to our findings. Fourth, SLDHS collected data only on 15–49-year-old women of reproductive age. However, with the current changes in adolescents’ actions and behaviors, there are children less than 15 years who have gone through a full cycle of reproductive health. As a result, we could not ascertain the distribution of underweight among females below 15 years. Finally, most data on predictors of underweight were based on self-reported information and were not verified through record analysis which risks socially acceptable answers, hence social desirability bias.
Generalizability of results
Results from this study can be generalized to low resource settings in low-and middle-income countries.