Introduction

Adolescence, which refers to the transition from puberty to adulthood spanning from ages 10 to 19, is a critical and unique period for both physical and psychological development. During this second phase of rapid growth in lives, adolescents establish their behavioral patterns, including those related to diet and physical activity. And the dietary patterns adopted during this stage lay the foundation for future health [1]. With the socio-economic development, the prevalence of malnutrition has gradually declined. However, the problem of adolescent obesity and nutritional imbalance has intensified due to societal civilization, diversification of diets and changes in lifestyles [2]. The dietary patterns of adolescents are also influenced by multiple factors, including social environment, family background, interpersonal relationships and individual factors such as mental, physiological, and lifestyle factors. At this phase, peers have a greater influence than parents. Common issues include irregular eating habits, frequent consumption of high-calorie and high-sugar foods, inappropriate dieting and insufficient physical activity. These unhealthy eating behaviors and lifestyles can contribute to a range of health issues, such as underweight or overweight due to imbalanced calorie consumption, inadequate vitamins and minerals intakes, as well as eating disorders like anorexia nervosa and binge eating disorder [3-5]. Among these issues, the consumption of energy-dense foods which are high in fat and sugar, coupled with sedentary behavior and lack of physical activity are the major causes of obesity and overweight [6]. Obesity during childhood and adolescence is likely to persist into adulthood, posing multiple risks to the cardiovascular, endocrine, respiratory, liver, musculoskeletal, psychological and cognitive systems, and placing long-term burdens on society in terms of economics and healthcare [7,8].

According to data from the World Health Organization (WHO), the prevalence of overweight and obesity among children and adolescents aged 5 to 19 increased from 4% in 1975 to 18% in 2016, representing a more than four-fold increase [6,9]. A study analyzing data from seven national surveys on the physical fitness and health of Chinese students revealed that the prevalence of overweight and obesity among Chinese children and adolescents aged 7 to 18 increased from 1.2% in 1985 to 23.4% in 2019, with an increase of more than 18 times. The prevalence was higher in boys than girls (28.4% and 18.4%) and higher in urban areas than rural areas (25.4% and 21.5%). Among provinces, Shandong had the highest prevalence (38.9%), while Guangdong had the lowest (12.2%) [10]. In Hong Kong, the Survey on Physical Fitness of Secondary School Students in 2019/20 and 2020/21 reported a higher prevalence of overweight and obesity compared to the 2014/15 academic year. The survey found that 32.1% of boys and 20.8% of girls were classified as overweight or obese, with an increase of 9.1% and 0.8% respectively compared to the figures recorded in 2014/15 [11]. In Macao, a survey conducted in 2018 regarding food consumption among secondary school students indicated that the overall proportion of overweight and obese students was 23.3%, in which boys and girls are 30.1% and 16.8% respectively [12]. The fourth Macao Citizens’ Physical Fitness Monitoring conducted in 2020 showed an increase in the overweight and obesity rates among all students compared to 2015. For boys, the overall overweight and obesity rates were 31.0%, representing an increase of 4.8%. As for girls, although the overweight and obesity rates decreased by 2.0% to an overall rate of 17.0%, there was a notable increase of 1.9% in the rate of underweight, indicating that boys are more prone to overweight issues while girls tend to be overly concerned with maintaining a slim figure [13].

On the public health level, overweight, obesity and their related non-communicable diseases are largely preventable. Supportive environments and communities, including measures taken by the government, are fundamental and essential elements in shaping people’s choices for a healthy lifestyle. These measures encourage individuals in making accessible and affordable choices, including healthy and nutritious foods, as well as resources and environments that facilitate physical activity, thereby fostering healthy lifestyles and preventing overweight and obesity [6]. Addressing the causes of childhood and adolescent overweight and obesity requires a comprehensive approach that targets various stakeholders and environments, including individuals, families, schools, communities and government. Therefore, it is crucial to develop comprehensive intervention measures with the involvement of professionals [14]. Although the current weight status of Macao adolescents is known from the government’s monitoring of the physical fitness of Macao residents, the research report did not investigate the nutritional intake aspect. Therefore, this study aimed to explore the nutritional intake status of Macao secondary school students and provide appropriate recommendations.

Materials and Methods

Study design and recruitment

A cross-sectional descriptive method was applied in this study to investigate the secondary school students in Macao during the 2020/21 academic year, with a total of 27,627 students enrolled [15]. Stratified random cluster sampling was conducted by selecting 3 schools from a pool of 47 schools. From each selected school, one class was randomly chosen from every grade level, resulting in a sample of 18 classes.

Procedure

Data was gathered from a total of 18 classes within 3 schools. Following the acquisition of consent and coordination with the school directors, questionnaires were distributed to each class. The researcher presented a slideshow featuring images of various food items alongside their corresponding names, portion sizes and actual tableware at the site. The students independently completed the forms, providing estimations of the servings they consumed daily.

Ethical aspects

Participation in the study was completely voluntary and the anonymity of questionnaire was ensured for all respondents. Before administering the survey, the research objectives were clearly communicated to the participants, who were informed of their right to decline participation or withdraw from the study at any point. The questionnaires and research materials were handled with strict confidentiality. This study was approved by the Faculty of Medicine of the Macau University of Science and Technology.

Food frequency questionnaire (FFQ)

A questionnaire with 13 food groups, total 61 food items was developed according to the research objectives and relevant literature, followed by reliability and validity verification by seven experts specializing in public health, nutrition and epidemiology. To assist the subjects in differentiating between different types of food and their quantities, a supplementary tool in the form of a food map was applied, indicating the weight or volume of each food item. By analyzing the data collected in the survey, we were able to understand subjects’ intake status of energy and nutrients.

Data analysis

To determine the weight status of the students, the calculated body mass index (BMI) from height and weight would be matched with the “Growth Reference BMI-for-Age Percentiles for Children and Adolescents Aged 5-19” from the WHO, then classified into different categories, including severe thinness, thinness, normal weight, overweight, and obesity [16]. The energy and nutrients intake were derived from food composition database of China, Japan and Hong Kong according to the weight or volume of each food item [17-19]. All data was analyzed via IBM SPSS 24.0 (IBM, Armonk, New York, USA). Independent- samples T Test was used to assess the difference of energy and nutrients intake between genders in each age group. Statistical significance was set at p<0.05. The average daily energy and nutrients intake were reported as the mean and Standard Deviation (SD) for normally distributed variables, and as percentiles for variables with skewed distributions.

Results

General demographic characteristics of the subjects

A total of 432 questionnaires were distributed and 424 (98.1%) were obtained as valid questionnaires after screening and eliminating those were missed or filled-in inappropriately. Table 1 shows the distribution of the subjects according to the demographic characteristics.

Table 1: General demographic characteristics of the subjects (n = 424).

Body Mass Index (BMI)

The average BMI of all subjects was 20.6 ± 0.2 (kg/m2). Average BMI for male and female were 21.8 ± 0.4 (kg/m2) and 19.9 ± 0.2 (kg/m2), respectively. According to the BMI category [20,21], the subjects were classified into severe thinness, thinness, normal weight, overweight and obesity, and the distribution is shown in Table 2.

Table 2: Distribution of subjects’ BMI classification (n = 424).

Difference of energy and nutrients intake between genders in each age group

The difference of energy and nutrients intake between male and female subjects in each age group is shown in Tables 3-5. Compared with the DRIs [22-26], the energy intake of male in the <14-year-old and 14-17-year-old groups were significantly higher than in female (p<0.05 and p<0.001), in which the <14-year-old group having energy intake higher than the DRIs. Protein intake in the <14-year-old and 14-17-year-old groups were also significantly higher than in female (p<0.01 and p<0.001), being 2 times and 1.5 times more than the DRIs, respectively. These two groups also consumed more fat (p<0.001 and p<0.001) and phosphorus (p<0.05 and p<0.001), especially phosphorus exceeding the DRIs by more than double. However, the intakes of dietary fiber, vitamin A, vitamin D and calcium in male were inadequate. In female, the intake of carbohydrates was significantly lower than that of male in the 14-17-year-old group (p<0.001), and it was lower than the DRIs as well. This group also had inadequate intake in energy and various nutrients, including fat, dietary fiber, vitamin A, vitamin D, calcium and iodine, with daily intake below the DRIs.

Table 3: Daily intakes of energy and nutrients from food.

Table 4: Daily intakes of vitamins from food.

Table 5: Daily intakes of minerals from food.

Average daily energy intake from various food groups

Table 6 shows the mean and SD, and the percentile of average energy daily intake from all 13 food groups. Overall, cereals and grains are the primary sources of energy with 674.4 kcal, followed by other common foods and drinks with 304.4 kcal (including snacks like potato chips, biscuits, and sugary beverages) and livestock with 203.9 kcal. Food groups provided energy within 100-200 kcal included milk and dairy products and fruits. Other food groups with less than 100 kcal intake included poultry, seafood, soybean products, eggs, vegetables and legumes, nuts and seeds, starchy products and seaweed and mushrooms.

Table 6: Average daily energy intake from 13 food groups (kcal).

Discussion

Countries worldwide place significant emphasis on the well-being and proper development of children and adolescents, implementing a range of policies and measures to foster their overall health. Currently, 96 countries have developed dietary guidelines, and among them, 12 countries have formulated dietary guidelines specifically for school-aged children, aiming to guide their balanced diets and foster healthy behaviors [27]. The “Healthy China Action (2019-2030)” issued by the State Council of China includes “Action for Balanced Diet” and “Action for Health Promotion in Primary and Secondary Schools” as major initiatives. In recent years, the nutritional status of Chinese children had shown significant improvement, reflected in the increase in average height and weight. According to the “Report on Nutrition and Chronic Diseases among Chinese Residents (2020)”, the rate of growth retardation among children and adolescents aged 6-17 had decreased from 4.7% to 2.2% [28]. However, with the changes in social and lifestyle patterns, they also faced challenges of malnutrition, overweight and obesity and micronutrient deficiencies. In the sixth national nutrition survey conducted between 2015 and 2017, compared to 1982, the prevalence of overweight and obesity had risen from 1.3% to 22.7% among boys and from 1.4% to 14.9% among girls. Micronutrient deficiencies, such as inadequate intakes of calcium, iron, vitamin A and vitamin D are also common [29]. Currently, the average daily energy intake for Chinese adolescents aged 12-17 is 1995.0 kcal, with carbohydrate intake of 253.8 g, protein intake of 61.4 g and fat intake of 84.5 g. The energy contribution ratios of these three macronutrients are 50.6%, 12.3%, and 37.1% respectively. Overall, in comparison to the recommended percentages of energy intake from carbohydrates 50-65%, protein 10-15%, and fat 20-30% for a balanced diet of 2000-2400 kcal according to the DRIs, their protein intake is aligned with the recommended level. Nevertheless, their energy and carbohydrates intakes barely met the minimum requirements, while fat intake exceeded the recommended range, leading to an imbalanced energy contribution ratio of the three major macronutrients. In general, the average daily energy intake, carbohydrates intake, fat intake, and protein intake of adolescents aged 12-17 are higher in boys than in girls [30].