Neck Circumference as an Indicator of Overweight and Obesity in Young Adults

Neck circumference (NC) measurement is one of the simple screening measurements, that can be used as a marker of upper body fat distribution to notice overweight. The objective of this study is to evaluate the relationship between NC and overweight/obesity. In this cross-sectional study a total 198 college students (120 Female, 78 Male) aged 18-23 years were participated using convenience method. Anthropometric measurements of students were measured according to the guidelines of world health organization. Students with NC ≥37 cm for male and ≥34 cm for female and BMI ≥ 25 kg/m2 are identified as overweight. The percentages of the male and female students with BMI ≥ 25 kg/m2 were 9% and 15.8% respectively and with high NC were 47.4% and 23.3 % respectively. In both male and female students, there were significant and positive correlation of neck circumference with body weight (male, r=0.572; female, r=0.629; p=0.001), waist circumference (male, r= 0.407; female, r= 0.623; p=0.001), hip circumference (male, r=0.546; female, r=0.579; p=0.001), BMI (male, r= 0.532; female, r= 0.588; p=0.001), waist to hip ratio (female, r = .376; p= .001), and waist to height ratio (male, r= 0.33; female, r= 0.574; p=0.001). A significant and independent association was found between NC and overweight levels using multiple regression analysis in young adults. This study indicates neck circumference is a simple screening measure that can be used to identify overweight/obesity.


Introduction
Overweight and obesity are defined as abnormal or excessive fat accumulation that may impair health [1]. Overweight or obesity, significantly, once it happens in students, may be a major health problem. There are mainly four types of assessment to determine obesity: anthropometry, density, conductivity, and radiography. For health purposes, the percentage of body fat and its distribution are significant factors, but determining this factor is not easy. Different assessment methods yield different results, some more accurate than others [2,3].
The most widely used technique of calculating and identifying obesity is Body Mass Index (BMI). In adults Overweight, or pre-obesity, is defined as a BMI of 25-29.9 kg/m², while a BMI ≥ 30 kg/m² defines obesity [4]. BMI is a simple measure that is very useful for population not individual basis. It is considered as a rough guide for predicting risk in individuals because it provides ranges based on height and weight which often don't take into account differences in ethnicity, age, body build, and muscle development.
Other methods include neck circumference, waist circumference, hip circumferences, waist to height ratio, and waist to hip ratio. Waist circumference is an inexpensive and cool method of measurement that is considered a rational marker of intra-abdominal or visceral fat. This fat is diligently related with increased risk of comorbidity [5]. Obviously, waist circumference is based on averages, so if people are outside the average in height or body build; waist circumference alone may not be an accurate measure [6,7].
The waist to hip ratio (WHR) is a simple measure of central obesity. The score from the WHR predicts the risk of developing several conditions associated with excess abdominal fat [5]. Researches show that the amount of abdominal fat correlates with the degree of stress, so it is hard to determine which is the causative factor in health problems-the fat or the stress or some combination of both. Nevertheless, the WHR is an important determinant of risk [8,9]. Waist to height ratio (WHtR) is a measure of the distribution of body fat that indicates the risk of obesity related diseases depending on the value of WHtR. It is calculated dividing waist circumference by height of a person [10]. The people with WHtR value ≥ 0.53 in male and ≥ 0.49 in female are categorized as overweight. It is considered as a better marker of abdominal obesity that corrects the waist circumference according to the individual's height [11,12,13].
Neck circumference (NC) measurement has freshly been used to recognize overweight and obesity and is perceived to have significant correlation with age, body weight, waist circumference, hip circumferences, waist/hip ratio, and BMI for both genders [14]. Researchers have shown the use of neck circumference as a simple screening method to identify obesity and overweight [15]. NC is reflected as a marker of upper body obesity and correlates significantly with changes in systolic and diastolic blood pressure [16]. Hence, the available literature review has not recognized the single paramount anthropometric measure or marker to verify the association with overweight and obesity.
Many researches conducted in different part of the world suggest that neck circumference can be used as a simple screening measure of overweight and obesity [14,17]. In this regard, the purpose of this study was to examine the relationship between neck circumference and overweight and obesity and also it examines the association of other anthropometric measures with BMI for the prediction of overweight and obesity in students.

Materials and Method
The cross sectional study using convenience sampling method was conducted in DAV College, Kathmandu, Nepal during July to August 2017. Out of 355 students of Bachelor's level, 198 students age between 18 to 23 years participated in this study comprising 120 (60.6%) female and 78 (39.4%) male who were free from major health problems. The written consent was received from the students before conducting the study, and the ethical approval was obtained from the Research and Ethics Committee of the college.

Anthropometric Measurements and Indices
Each student's demographic information along with body weight, height, neck circumference (NC), waist circumference, and hip circumference were measured by the researcher following WHO standard. All measurements were taken in the morning time. The student's body weight was measured to the nearest (0.1 kg) wearing light clothes and taking off shoes using analog weighing scale. Height was measured without shoes to the nearest (10 mm) using stadiometer. Body Mass Index was computed as dividing weight in kg by height in m 2 . According to WHO classification [18], the students were classified into four categories in accordance with the BMI values of <18.5 kg/m 2 as underweight, 18.5 to 24.99 kg/m 2 as normal weight, 25.0 to 29.99 kg/m 2 as overweight and ≥30kg/ m 2 as obese.
Circumferences were measured (in cm) using regular inelastic plastic tape with 0.5 cm precision. The measurements were taken while students were standing erect with the arms hanging loosely at sides. The hip circumference (HC) was obtained at the level of the femoral trochanters and the neck circumference was measured below the cricoid cartilage, and afterwards, at the level of the mid cervical spine using plastic tape. While taking this reading, the subject was asked to look straight ahead, with shoulders down, but not hunched. Care was taken not to involve the shoulder/neck muscles in the measurement.
Waist circumference (WC) was taken horizontally to the nearest 10 mm, using plastic tape measure at midpoint between the costal margin and iliac crest with the subject in standing position. WC was then divided by HC to get the waist-to-hip ratio (WHR). Students with waist circumferences >94 cm for male and >80cm for female are categorized as central obesity and with waist/hip ratio >0.90 for male and >0.85 for female considered as abdominal obesity. Waist to height ratio was obtained by dividing waist circumference by height of students. With waist to height ratio ≥ 0.53 for male and ≥ 0.49 for female students are grouped as overweight. Students with NC ≥37 cm for male and NC ≥34 cm for female were categorized as overweight [7].

Statistical Analysis
The statistical analysis was performed with SPSS version 23.0 for Windows. The outcomes were expressed as the mean ± standard deviation, range, and percentages. Pearson's correlation coefficient was used to determine the relation between various anthropometric indices for continuous variables. A p-value <0.05 was considered to be significant. Multiple regression model was performed to determine the possible relationship of each predictor variables with the outcome variable. Goodness of fit was measured by coefficient of determination R 2 .

Results
Of the 198 students that participated in the study, 78 (39.39%) were male and 120 (60.6%) females. The range of age of the participants was 18 to 23 years. The mean BMI was 21.24± 2.67 kg/m 2 for male, 21.68 ±2.9 kg/m 2 for female. The 8.97% of the male and 15.8 % of the female were overweight (BMI ≥25kg/m 2 ). The mean waist circumference and hip circumference of the male and female were 79.4±6.95 cm, 94.7±5.39 cm and 72.5±7.82 cm, 92.78±6.05 cm, respectively. This study has observed 1.3% of male and 15.8% of female students with high waist circumference. The mean waist/hip ratio was 0.837±0.046 in male, 0.781±0.059 in female. The male and female students with high waist//hip ratio were 9% and 12.5% respectively. The average waist to height ratio of male and female students were 0.46±0.041and 0.46±0.049 respectively. The percentage of male and female students with high waist to height ratio and categorized as overweight were 9% and 33.3% respectively. The mean neck circumference of male and female were 36.51±2.026 cm and 32.58±1.81cm respectively. The 47.4% of male and 23.3% of female students neck circumference measurements were higher and grouped as overweight students. The summary output described in Table 1 is produced using the options in the Linear Regression Statistics dialog box. This table tells the mean and standard deviation of each variable used in the study.
The Pearson's correlation coefficient is particularly useful for getting a jagged idea of the associations between predictor and the outcome variables. Table 2 presents the BMI is significantly and positively correlated with waist circumference, hip circumference, waist to hip ratio, waist to height ratio and neck circumference for male and female. The one-tailed significance of each correlation is demonstrated as p < 0.001.    The model summary output (Table 4) of multiple regression analysis using enter method describes the overall model and tells the model is successful in predicting outcome BMI with predictors waist to height ratio, neck circumference, hip circumference, waist/hip ratio, and waist circumference. In the regression model for female, the multiple correlation coefficient between the predictors and the outcome variable BMI is R=0.896. The value of R 2 = 0.80 indicates 80% variability in dependent variable BMI is explained by the predictors but remaining 20% is unexplained. The difference between R 2 and adjusted R 2 is 0.802 -0.793 = 0.009 about 0.9%. It shows if the model was derived from the population rather than a sample it would account for nearly 0.9% less variance the outcome.
The p-value is less than the significance level in F test (ANOVA) it means sample data provide sufficient evidence to conclude that the regression model fits the data better than the model with no independent variable. In multiple regression analysis, multi-collinearity tested and only neck circumference (Beta: 0.153, 95% CI: 0.046-0.36, p<0.001) for male and (Beta: 0.129, 95% CI: 0.031-0.381, p<0.001) for female was found to be independently associated with BMI. The positive beta coefficient indicates that for every one-unit increase in the neck circumference, the BMI will increase by the beta coefficient value [19,20].

Discussion
World Health Organization [18] defines overweight and obesity as abnormal or excessive fat accumulation that presents a risk to health. Overweight and obesity are chief possibility factors for a number of prolonged diseases such as diabetes, cardiovascular diseases, and cancer. Once considered a problem only in high-income countries, overweight and obesity are now dramatically on the rise in low-and middle-income countries, particularly in urban settings. According to WHO report, in 2016, more than 1.9 billion adults, 18 years and older, were overweight. Of these over 650 million were obese. 39% of adults aged 18 years and over were overweight in 2016, and 13% were obese. Most of the world's population lives in countries where overweight and obesity kills more people than underweight [4]. Some Asian countries have mean BMIs that are among the lowest in the world. But even Bangladesh and other countries where under-nutrition remains a significant threat-Cambodia, China, India, Nepal, and Vietnam-have seen the prevalence of overweight and obesity in women increase from the 1990s through the mid-2000, by anywhere from 3.5 to 38.5 percent a year [21]. There are several methods of measuring overweight and obesity. Several sophisticated methods, such as magnetic resonance imaging, and bioelectrical impedance, can't be used in children or students due to safety concerns [22,32].
A study of 14,425 subjects in Nepal found that 32% were obese, 28% were overweight, 6.3% were diabetic, and 34% had hypertension. Prevalence was higher in the less educated, those working at home, and female [23]. On the basis of BMI, among Nepalese population, the proportion of male respondents who were overweight and obese was 11.8% and 1.5% and the proportion of overweight and obese in female respondent was found to be 12.3% and 2% in the age group 15 -29 years [24].
In this study, the mean BMI was 21.24 kg/m 2 for male, 21.68 kg/m 2 for female. This shows the female students were more overweight than the male students. This result is consistent with the previous studies. This study result shows among the male students, 14.1% underweight, 76.9% normal weight, and 8.97% overweight. Among female students 15% underweight, 69.2% normal weight, and 15.8% overweight were obtained based on the BMI categories.
The most basic and common method to determine overweight is the body mass index (BMI). But BMI is considered as an indirect and insufficient measurement which does not distinguish between body fat and lean body mass [22,25]. For the evaluation of central obesity, other anthropometric measures are used. Among other anthropometric measures, waist circumference, hip circumferences, waist-to-hip ratio, waist to height ration and neck circumference are useful in clinics and community settings, as well as in large research studies [26,27].
Waist circumference is the easiest way to measure "abdominal obesity"-the additional fat found around the middle but the measurement procedure has not been standardized. On the basis of WHO report, the waist circumference cutoff for Asians was suggested as 90 cm for adult men and 80 cm for adult women, but it differs from one ethnic group to the other. Waist-to-hip ratio (WHR) is also used to measure abdominal obesity but it is more complex to interpret than waist circumference, since increased waist/hip ratio can be caused by increased abdominal fat or decrease in slender muscle mass around the hips. Turning the waist and hip circumference measurements into a ratio leads to a loss of information: Two people with very different BMIs could have the same waist to hip ratio [22,28,31].
This research shows the mean waist circumference and hip circumference of the male and female students were 79.4 cm, 94.7cm and 72.5 cm, 92.78 cm, respectively.
According to WHO standards (WC >94 cm for male, WC >80cm for female), this study found 1.3% of male and 15.8% of female had high waist circumference which indicates there could be increased risk of metabolic complications among the study subjects. In present study, the mean waist to hip ratio of male and female students was 0.837and 0.781respectively. The value of waist to hip ratio shows there is possibility of substantially increased risk of metabolic complications for 9% male and 12.5% female students. The mean waist to height ratio of male and female students was 0.459 and 0.46 respectively. The percentage of male and female students who are grouped as overweight on the basis of waist to height ratio were 9% and 33.3% respectively.
In one of the research paper it was mentioned that the waist to height ratio sustains significant and variable enduring correlation with height over adolescence [6]. The waist-to-height ratio has been suggested as a useful measure, with a suggested cut-off of 0.5 signifying excess risk [29]. In this study, the percentage of male and female students with excessive waist to height ratio and categorized as overweight were 9% and 33.3% respectively.
In present study, the mean neck circumference (NC) of male and female students was found to be 36.5 cm and 32.5 cm respectively. The 47.4% of male and 23.3% of female student's NC measurements were higher than the standards for male and female respectively. In both male and female, neck circumference was correlated significantly and positively with body weight, waist circumference, hip circumferences, BMI, and waist to height ratio but for female students only NC is correlated significantly with waist to hip ratio (p< 0.05). This is consistent with some researches that have observed the relationship of conventional anthropometric measures of overweight/obesity with neck circumference [15,30]. The multiple regression model shows that neck circumference is independent predictor for overweight based on BMI for both male and female. Hence, it can be concluded that neck circumference is an effective indicator for identifying overweight individuals and correlated significantly with other anthropometric measurements.
This study has limitations such as data related to student's dietary habits, physical activity, biochemical measurements etc. were not collected.

Conclusion
To sum up, this study presents, in both male and female, there was a significant correlation between neck circumference and specific anthropometric measurements such as body weight, waist circumference, hip circumferences, waist to height ratio, and BMI. The 8.97% of the male and 15.8 % of the female were observed as overweight. Neck circumference is a significant predictor of overweight based on BMI among the college students. So, it can be used as a simple screening measure to identify overweight and obese among students, remarkably for clinical practices and epidemiological investigation. Additionally, more extended researches including body fat and other biochemistry measurements can be conducted for identifying overweight and obesity.

Financial Support and Sponsorship
Nil.