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INTRODUCTION
Recent global societal shifts have significantly altered household compositions, resulting in a rapid increase in single-person households. This is particularly evident in South Korea, where single-person households have become the predominant household type. Single-person households accounted for 31.7% (6.643 million) of South Korea's households in 2020, rising to 33.4% (7.2 million) in 2021, surpassing traditional multi-person households of 4 or more persons by up to 1.8 times. This number of single-person households is estimated to continue to increase, reaching 8.3 million by 2030 and 9.05 million by 2050 [1].
The prevalence of single-person households among middle-aged adults has also increased notably, mirroring the increase in social isolation in this demographic group. The number of single-person households among middle-aged adults increased significantly, from 539,000 in 2000 to 1.618 million in 2015 [2]. Over the same period, the proportion of adults aged 35–64 yrs in all single-person households increased from 39.9% to 48.1%. The factors contributing to this surge in single-person households among middle-aged adults include single marital status, divorce, bereavement, and family breakdown.
Household structure significantly influences dietary patterns and health outcomes. In single-person households, where food responsibilities are borne solely by the adults, dietary habits exhibit unique characteristics that are influenced by attitudes toward eating and health consciousness. Undesirable lifestyle habits, such as irregular meal patterns, skipping meals, smoking, and excessive alcohol consumption, are commonly observed in this demographic group [345]. Processed foods, convenience foods, and eating out are often preferred over preparing meals with fresh ingredients [67], leading to an inadequate intake of healthy foods such as vegetables, fruits, and fish [8].
Previous studies have highlighted the prevalence of dietary issues among middle-aged adults living alone, who skip breakfast at a higher rate [91011], are more likely to eat alone or eat out [10111213], and have a generally lower food security level [9] compared with those in the same age range living in multi-person households. As a result, reduced intakes of proteins, major minerals, and vitamins are also frequently noted in this demographic population [11], contributing to poorer overall health outcomes and a higher prevalence of metabolic syndrome compared with people living in multi-person households [91114].
Single-person households comprising middle-aged adults may face challenges such as economic hardships and social isolation, which can exacerbate dietary problems. The eating habits of middle-aged adults are directly linked to the risk of chronic diseases, with the quality of food choices playing a critical role in overall health [915]. Studies have shown that balanced nutrition and regular meal patterns significantly reduce the risk of metabolic syndrome and cardiovascular diseases [161718]. Therefore, considering the onset of several metabolic abnormalities in this age range, effective dietary interventions are crucial. Strengthening food and cooking skills may be a viable solution for improving the dietary quality of middle-aged adults living alone. Cooking competency positively influences eating behavior [19202122]. For instance, individuals with better cooking skills are less likely to choose convenience or processed foods, and are more likely to consume vegetables [23242526].
Self-efficacy related to cooking skills is associated with healthier food consumption [2728]. Individuals with high confidence in their cooking and nutrition knowledge are more likely to recognize the importance of vegetable consumption and select products based on ingredients and nutritional information labels [29]. Those with higher diet quality scores also showed greater confidence in their cooking and food skills and lower consumption of takeout foods [30].
Cooking and food skills vary according to sex and age, with older adults and female typically exhibiting higher skills [30]. Adults who live alone often have lower vegetable intakes due to a lack of the necessary skills to prepare vegetable-based meals [3132]. Lower cooking skills have also been linked to higher mortality risk, particularly among those living alone [33]. Therefore, there is a need to deepen the current understanding of eating habits and behaviors, dining and cooking environments, and cooking and purchasing capabilities. Such understanding may be essential for developing targeted intervention and education programs aimed at promoting healthier eating behaviors among middle-aged adults living alone.
While previous research has primarily focused on dietary issues among older adults who live alone, this study examined the dietary habits, cooking behaviors, and purchasing environments of middle-aged adults (aged 35–64 yrs) living alone. By analyzing the effect of dietary competencies and cooking skills on healthy eating habits, this study provides foundational insights for developing efficient dietary management intervention programs for this demographic group.
SUBJECTS AND METHODS
Study population and survey
To investigate dietary characteristics, dietary competencies, cooking skills, and their relationship with nutritional quotient (NQ) in middle-aged adults (aged 35–64 yrs) living alone, an online survey was conducted between April 20–26 of 2023 that targeted this demographic group. A professional online survey agency recruited 500 registered panelists from various regions. The survey considered sex, age group, and residential area (metropolitan and non-metropolitan). Only those who had lived alone for at least 6 mon were included, and all participants provided written informed consent prior to the study. This study was approved by the Institutional Review Board (IRB) of Korea National University of Transportation (approval No. KNUT IRB 2023-06).
Study instrument
The questionnaire for this study was developed by modifying and supplementing the items used in previous studies [343536] to fit the study's objectives. The survey questions included general information (educational level, economic activity, marital status, period of living alone, smoking status, frequency of alcohol consumption, and regular exercise), eating habits (frequency of meals, reasons for skipping meals when eating alone, frequency of consumption of vegetables, fruits, milk, and dairy products, and reasons for not consuming these), awareness of eating habits (dietary satisfaction, awareness of one's own healthy diet), cooking environment (space, equipment, utensils, storage space, seasonings), food purchasing environment (availability of grocery stores with various and healthy food, appropriateness of prices, etc.), dietary competencies (5 questions), and cooking skills (5 questions) of the participants.
Awareness of healthy diet, cooking environment, food purchase environment, dietary competencies, and cooking skills were measured on a 5-point Likert scale. The scale ranged from "1 (strongly disagree)" to "5 (strongly agree)". Satisfaction with diet was scored from "1 (very dissatisfied)" to "5 (very satisfied)". To evaluate the quality of meals and nutritional statuses of the respondents, the questionnaire also included items from the NQ for Korean adults [36]. The NQ developed by the Ministry of Food and Drug Safety is a tool created to comprehensively evaluate the eating behavior, meal quality, and nutritional status of an individual or group. The NQ for adults comprises a total of 18 questions and is divided into 3 areas: balance, moderation, and practice. The initial questionnaire was finalized after a preliminary survey of 15 middle-aged adults living alone, the items were revised and supplemented based on the results of the preliminary survey.
Data analysis
All the data were analyzed using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). For continuous variables, means and standard deviations were calculated. Unweighted numbers and weighted percentages were calculated for the categorical variables. Differences by sex and age group (35–49 and 50–64 yrs) were analyzed using Student's t-test for continuous variables and χ2 test for categorical variables.
The relationships between dietary competencies, cooking skills, and NQ scores (for balance, moderation, practice, as well as total scores) were determined using logistic regression analysis. This analysis was adjusted for relevant variables that showed significant differences among the participants, by calculating the adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs). All significance testing was performed with an α-level of 0.05. NQ scores for balance, moderation, practice, and total scores were divided into quartiles to facilitate the analysis.
RESULTS
General characteristics of the respondents
The general characteristics of the middle-aged adults living alone according to sex and age group are presented in Table 1. The average age of the respondents was 48.83 yrs, and 74.40% had college degrees or higher educational levels. Among the respondents, 61.40% were single and 25.60% were widowed or divorced. Based on the age group, adults aged 35–49 yrs had significantly higher proportions of respondents who had a college degree or higher educational levels (P = 0.001), who were engaged in economic activities (P < 0.001), and who were single (P < 0.001), compared with those aged 50–64 yrs.
Table 1
General characteristics of the middle-aged adults living alone according to sex and age
The average duration of living alone was 124.55 mon. While no significant difference was observed by sex, this duration was significantly longer in the 50–64 yrs age group (138.34 mon) compared with in the 35–49 yrs age group (112.22 mon; P = 0.002). Regarding alcohol consumption, the proportion of respondents who reported no alcohol consumption at all over the preceding year was higher among female (40.40%) than that among male (21.20%), and higher among the 50–64 yrs age group (38.98%) than that among the 35–49 yrs age group (23.48%).
Dietary status
The eating habits of the respondents according to sex and age group are presented in Table 2. Our analysis of meal frequency showed mean frequencies of 3.01 times/wk, 5.92 times/wk, and 5.85 times/week for breakfast, lunch, and dinner, respectively. For dinner, male exhibited a significantly higher meal frequency (6.10 times/wk) than female (5.59 times/wk; P < 0.001).
Table 2
Eating habits of the middle-aged adults living alone according to sex and age
Values are presented as mean ± SD or number (%).
1)P-value by Student's t-test or the χ2 test.
2)Multiple response.
3)Very dissatisfied (1)–very satisfied (5).
4)Strongly disagree (1)–strongly agree (5).
5)Adjusted for smoking status and frequency of alcohol consumption.
6)Adjusted for educational level, economic activity, marital status, duration of living alone and frequency of alcohol consumption.
The most common reason for skipping meals when eating alone was “because it is a hassle to prepare meals” (80.20%). Male had a higher response rate of “because I don't know how to cook” (10.80%) than female (1.60%), whereas female were more likely to respond that they skipped meals when eating alone “for diet reasons” (38.40%) compared with male (18.80%; P < 0.001). The respondents’ levels of satisfaction with their diet and awareness of their own healthy diet were 3.07 and 2.77 out of 5.0 points, respectively, with no significant differences according to sex and age.
Table 3 presents the participants’ frequencies of consuming vegetable, fruit, and milk and dairy products consumption, and the reasons for not consuming them. The proportion of participants who consumed vegetables once per day was the highest, at 28.60%, with significant differences observed according to age (P = 0.011). The most common reason for not consuming vegetables was “because the quantity for sale is too large to eat alone” (64.79%). In the case of male, the proportion of the respondents who responded that they do not eat vegetables “because it is difficult to prepare or cook” was significantly higher than that of female (P = 0.003). The proportion of respondents in the 35–49 yrs age group who responded, “because it is difficult to dispose of the resultant food waste” was significantly higher than that in the 50–64 yrs age group (P = 0.035).
Table 3
Frequencies of vegetable, fruit, and milk and dairy products consumption, and the reasons for not consuming of the middle-aged adults living alone according to sex and age
For fruit consumption, the proportion of the participants who responded that they consumed fruit less than once every 2 weeks was the highest, at 34.20%, with significant differences according to sex and age. Female consumed fruits significantly more frequently than male did (P < 0.001). The most common reason for not consuming fruits was “because it is expensive” (54.17%). The proportion of the participants who responded that they consumed milk 1–3 times per week was the highest, at 36.00%. The major reason for not consuming milk or dairy products was “because I do not like them” (53.56%). The number of male not consuming milk or dairy products “because it is expensive” was significantly higher than that of female (P < 0.001). The proportion of respondents in the 35–49 yrs age range who reported not consuming milk or dairy products “because the quantity for sale is too large to eat alone” (P = 0.023), “due to a lack of storage space” (P = 0.0290),” and “because I do not like them” (P < 0.001) was significantly higher than that in the 50–64 yrs age group.
Dietary competencies and cooking skills
The results for the cooking and food purchase environments of the respondents are presented in Table 4. Sufficiency of cooking equipment had the highest score, at 3.91 points out of 5.0, followed by sufficiency of cooking utensils (3.83 points), sufficiency of food storage space (3.69 points), sufficiency of cooking space (3.46 points), and sufficiency of seasonings needed for cooking (3.30 points). All items in the cooking environment section differed significantly according to sex. Female scored higher than male in all these items.
Table 4
Cooking environment and food purchase environment of the middle-aged adults living alone according to sex and age
Values are presented as mean ± SD.
1)Strongly disagree (1)–strongly agree (5).
2)P-value by Student's t-test.
3)Adjusted for smoking status and frequency of alcohol consumption.
4)Adjusted for educational level, economic activity, marital status, duration of living alone and frequency of alcohol consumption.
Regarding the food purchase environment of the residential area, “There are grocery stores near my house where I can purchase variety of healthy foods” had the highest score, at 3.71 points, followed by “There is a grocery store close to my house where I can purchase variety of healthy foods” (3.58 points), “The foods sold at the grocery stores near my house are fresh and of good quality” (3.47 points), “The services of a grocery store near my house are convenient to use” (3.33 points), and “The foods sold at the grocery stores near my house are reasonably priced for me to purchase” (3.30 points). Female had higher scores than male for most of the items related to cooking and purchasing environments in residential areas.
Table 5 presents the results for dietary competencies and cooking skills. Among all of the respondents, the score for the “I know about the impact of food choices on health” was the highest, at 3.36 points. In the case of cooking skills, “I can handle simple cooking appliances and cooking utensils” had the highest score, at 3.95 points. Female scored significantly higher than male in dietary competency (P = 0.003) and cooking capability (P = 0.001).
Table 5
Dietary competencies and cooking skills of the middle-aged adults living alone according to sex and age
Values are presented as mean ± SD.
1)Strongly disagree (1)–strongly agree (5).
2)P-value by Student's t-test.
3)Adjusted for smoking status and frequency of alcohol consumption.
4)Adjusted for educational level, economic activity, marital status, duration of living alone and frequency of alcohol consumption.
Relationship with nutrient quotient
The NQ score of all the participants was 53.97 points (Table 6). The mean scores for balance, moderation, and practice were 32.75, 67.33, and 59.85 points, respectively. No significant differences were found according to sex; however, significant differences were observed according to age. Balance (P = 0.003), moderation (P < 0.001), and total NQ scores (P = 0.001) were significantly higher in those aged 50–64 yrs than in those aged 35–49 yrs. The distribution of the NQ scores showed significant differences according to sex and age. In particular, the low scoring group had a significantly higher proportion of male (60.00%) than of female (38.80%).
Table 6
NQ of the middle-aged adults living alone according to sex and age
Values are presented as mean ± SD.
NQ, nutrition quotient.
1)P-value by Student's t-test or the χ2 test.
2)Adjusted for smoking status and frequency of alcohol consumption.
3)Adjusted for educational level, economic activity, marital status, duration of living alone and frequency of alcohol consumption.
4)Low: 0–52.737 points, middle: 52.738–68.482 points, high: 68.483–100 points.
Analyzing the impact of dietary competency on NQ score (Table 7), we found that higher dietary competency scores in balance, practice, and total NQ scores, excluding moderation, correlated with significantly higher scores on each item (P for trend < 0.001). In the case of the total NQ scores, it was 1.67 in Q2, 2.71 in Q3, and 3.75 in Q4, indicating that this score increased significantly as the dietary competency score increased. In particular, in the case of adults aged 35–49 yrs living alone, higher dietary competency scores correlated significantly with higher NQ scores (P for trend < 0.001).
Table 7
Adjusted ORs and 95% CIs of high nutrition quotient score by dietary competency in middle-aged adults living alone
OR, odds ratio; CI, confidence interval.
1)Adjusted for educational level and regular exercise.
2)Adjusted for smoking status.
3)Adjusted for age, sex, educational level and smoking status.
4)Adjusted for sex and smoking status.
5)Adjusted for sex, educational level, marital status, smoking status and regular exercise.
6)P for trend by logistic regression analysis.
Our analysis of the NQ scores according to the level of cooking capability (Table 8) showed that the adjusted OR increased significantly as the cooking capability score increased for all of the items, as well as the total NQ score. In the case of the NQ, compared with the Q1 group with the lowest cooking capability score, the OR for the Q2, Q3, and Q4 groups were 1.95, 2.34, and 3.99, respectively. Therefore, the group with the highest cooking capability score also had a higher NQ score (P for trend < 0.001).
Table 8
Adjusted ORs and 95% CIs of high nutrition quotient score by cooking skill in middle-aged adults living alone
DISCUSSION
In this study, an online survey was conducted targeting 500 middle-aged adults (aged 35–64 yrs) living alone, to determine their eating habits, food-related environments (i.e., cooking and purchasing environment), dietary competencies, and cooking skills, as well as their relationships with the NQ score. The survey results revealed that middle-aged adults living alone cited difficulties related to meal preparation and cleaning up after meals as the main reasons for skipping meals when eating alone. In addition, the consumption of vegetables, fruits, and milk among middle-aged adults living alone was lower than the recommended level. An analysis of the NQ score—a comprehensive indicator that can be used to evaluate the quality of an individual’s diet—revealed that the mean score was 53.97 points. The dietary competencies of middle-aged adults living alone were lower than their cooking skills, and higher dietary competencies and cooking skills were significantly associated with increased NQ scores in this population. These results are expected to be useful for developing targeted nutrition education interventions for single-person households.
Individuals living alone prepare their own meals and are responsible for their own dietary intake. These characteristics affect their eating habits, such as increased consumption of processed foods or convenience foods, decreased intake of fruits and vegetables, and skipping meals. Adults living alone also seek convenience, rely heavily on eating out, skip meals frequently, have irregular meal times, and often eat alone [3738]. Hong and Kim [10] used raw data from the Food Consumption Behavior Survey to report that adults in their 40s and 50s who lived alone had a significantly higher rate of skipping breakfast than those who were a part of multi-person households and those who responded that they eat regularly. In the present study, the consumption frequencies of breakfast, lunch, and dinner per week for middle-aged adults (aged 35–64 yrs) living alone were 3.01, 5.92, and 5.85, respectively, indicating that they skipped breakfast ≤ 4 times per week, and skipped lunch and dinner more than once per week. Compared with female, more middle-aged male in single-person households skipped meals when eating alone because they did not know how to cook food or had to clean up themselves. The rate at which male aged 50–64 yrs living alone skipped meals was significantly higher than that among female in that demographic group.
In the case of middle-aged female living alone, the frequency of eating dinner was significantly lower than that in male, which may be related to the high desire to control weight as a reason for skipping meals when eating alone. Skipping meals can result in an insufficient supply of nutrients needed for the day, or cause overeating during the next meal. In addition, considering previous studies which reported that meal skipping is closely related to an inappropriate cardiometabolic profile or metabolic syndrome [3940], it is necessary to suggest various methods to stop meal skipping in middle-aged single-person households and especially single-male households. In addition, customized intervention measures based on the reasons for skipping meals when eating alone, such as cooking education or increasing opportunities to eat together, are necessary.
This study found that the proportion of middle-aged adults living alone who consumed vegetables and fruits more than once per day were 50.20% and 21.80%, respectively, which was not high. The importance of vegetable and fruit intake in the diet is increasing. Particularly in South Korea, dietary habits are shifting toward a Western style. Among adults living alone, vegetable and fruit intake is becoming increasingly low [841]. In a study that analyzed raw data from the 2017–2021 National Health and Nutrition Examination Survey, adults aged ≥ 19 yrs living alone showed significantly lower ORs for consuming > 500 g/day of fruits and vegetables compared with adults living in multi-person households. A stratification analysis showed the same results, regardless of household type, only for those aged ≥ 65 yrs [42].
As this study was conducted only on middle-aged adults living alone, it is difficult to clearly present the differences between single-person and multi-person households. However, in this study, a high proportion of middle-aged male (aged 35–49 yrs) among the adults living alone responded that they did not consume vegetables and fruits because they found it difficult to clean or dispose of the resultant food waste. This result is similar to that of previous studies showing that adults living alone lack the time to cook vegetables or do not have the skills to prepare vegetable-based dishes, thereby resulting in low vegetable intake [3132]. Reduced vegetable and fruit intake is a common phenomenon among adults living alone [84142]; the rich micronutrients and bioactive substances contained in vegetables and fruits help to prevent various chronic diseases. Considering that it is very helpful for health [4344], it is necessary to consider various ways of increasing vegetable and fruit intake in middle-aged adults living alone. In particular, changes in the food environment that can increase the intake of vegetables and fruits, such as selling vegetables in smaller quantities or providing spaces to store food, would likely be beneficial. When conducting educational programs for middle-aged adults living alone, it is necessary to prioritize topics, such as how to care for vegetables and fruits and the importance of eating them to prevent chronic diseases.
The mean balance, moderation, and practice scores among our participants were 32.75, 67.33, and 59.85 points, respectively, and the mean total NQ score was 53.97 points. When compared with the average total NQ score of adults nationwide (60.8 points) [36], the NQ score in our participant group was very low. In particular, those aged 35–49 yrs showed significantly lower scores. Previous studies have also shown that the nutritional statuses of individuals living alone are generally lower than those of individuals living in multi-person households. According to a previous study targeting middle-aged male of 40–60 yrs, the dietary evaluation index of single-person households was significantly lower than that of multiple-person ones, particularly for breakfast. Single-person households have also reported lower dietary, grain, and fruit intake scores than multi-person ones [45].
In a survey of Spanish adults aged 18–45 yrs, single-person households had significantly lower healthy eating indexes than multi-person ones, and the frequency of consumption of fast, fried, and ultra-processed foods was high, whereas that of fish was low [46]. The present study, as well as several previous studies, have reported that the nutritional statuses of middle-aged adults living alone tend to be worse than those of adults living in multi-person households. Therefore, it is important to uncover the underlying factors related to the nutritional statuses of middle-aged adults living alone, and improve their nutritional statuses through interventional programs.
Cooking skills play a crucial role in meal preparation, particularly when using raw ingredients. Food skills include meal planning, conceptualizing food, meal preparation, cooking techniques, food awareness, and knowledge of nutritious and hygienic foods [47]. Cooking and food skills are closely related to food selection and health outcomes. Adults with higher cooking skills are less likely to choose convenience or processed foods, and are more likely to consume more vegetables [23242526]. Additionally, cooking and food skills differed depending on sex and age, with older adults and female tending to have better cooking and food skills [30].
Self-efficacy related to these cooking skills is associated with healthier food consumption [2728]. In a study conducted in Australia, when groups were classified according to their levels of confidence in food technology and nutritional knowledge, the importance of consuming fresh food and vegetables and the rate of reading and choosing based on product information (e.g., ingredients and nutritional labels) increased when confidence was high [29]. The present study investigated the dietary competencies and cooking skills of middle-aged adults living alone, and found that female had higher dietary competencies and cooking skills than male. Although the dietary competencies and cooking skills in this study differed from those investigated in previous studies [262930], female generally appeared to have higher competencies than male. Therefore, various methods should be implemented to improve dietary competencies and cooking skills in middle-aged and older male living alone, including conducting cooking classes and providing recipes.
Analyzing the relationships between dietary competencies, cooking skills, and the NQ score showed that higher dietary competencies and cooking skills correlated significantly with higher NQ score. These results are similar to those of a previous study [30], which showed that adults with high diet quality scores had higher levels of confidence in their cooking and food skills, and lower levels of consumption of takeaway foods. Adults with lower cooking skills have higher risk of death; however, this was only observed among those who were living alone [33]. Therefore, customized education is warranted to improve the dietary competencies and cooking skills of middle-aged adults and single-person households.
This study had several limitations. First, the participants were limited to middle-aged adults living alone; therefore, characteristics could not be compared between single- and multi-person households. However, the dietary characteristics of single- and multi-person households have been thoroughly examined in other previous studies [8104145]. The purpose of this study was to analyze the dietary habits, cooking behaviors, and purchasing environments of single-person households and to systematically analyze the relationship between these factors and nutritional status. Second, despite the fact that socioeconomic factors such as income and education level have an impact on nutrition and health, no comparative analysis was conducted with regard to the nutritional status of adults living alone according to their socioeconomic level. Third, although eating habits, dietary competencies, cooking skills, and NQ scores of middle-aged adults living alone were analyzed, the relationship between these factors and health outcomes was not. A previous study analyzing adults aged ≥ 19 yrs found that adults living alone had more inappropriate eating habits, such as skipping breakfast and eating meals irregularly, and significantly higher prevalence of metabolic syndrome than those living in multi-person households [48].
In addition, a 3-yr cohort study targeting older adults showed that lower cooking skills correlated with higher risk of death; however, this was only found in adults who lived alone [33]. Considering these results, detailed research regarding the relationship between dietary habits and nutritional statuses of middle-aged adults living alone and health indicators is warranted. Finally, because this was a cross-sectional study, the results were derived only for correlations, and causal relationships could not be revealed. Therefore, longitudinal studies are warranted to determine specifically how the dietary characteristics of adults living alone affect their nutritional statuses and future health indicators.
This study also had several notable strengths. First, when recruiting participants for this study, samples were extracted using proportional allocation by age group, sex, and residential area. This ensured a representative sampling of adults living alone from across the country, thereby making the results of this study more generalizable. Second, this study derived the dietary characteristics and intervention factors of middle-aged adults living alone, and subdivided them by age group and sex. Therefore, the results of this study may be useful as fundamental data for developing customized education programs for adults living alone based on age group and sex in dedicated centers for people living alone or health centers in the community.
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