General characteristics and instant noodle consumption survey

All of the students completed an online survey that ascertained demographic and socioeconomic factors, and health-related behaviors including age, height, weight, family income, alcohol consumption, smoking behavior, and physical activity. Family monthly income was classified into < $2000 USD, $2000-4000 USD, and > $4000 USD. Alcohol consumption was categorized as non-drinker, moderate drinker [weekly alcohol consumption < 14 drinks (males) or < 7 drinks (females), where 1 drink constitutes 14 g pure alcohol], and heavy drinker [weekly alcohol consumption > 14 drinks (males) or > 7 drinks (females)]. Smoking behavior was classified as non-smokers, ex-smokers, or current smokers, depending on current smoking status. Physical activity was classified as highly active (1500 MET-min/week, for any strenuous physical activity practiced > 3 d/week or 3000 MET-min/week, for any activity conducted daily), moderately active (intense physical activity for > 20 min/week or moderate activity or walking 5 d/week for > 30 min/d), or no physical activity/inactive (below a moderate level of physical activity).

Information on instant noodle consumption was obtained from the participants' answers to a question about their average frequency of instant noodle intake over the 1 year period prior to the survey. The questionnaire listed several potential candidate foods important for cardiometabolic risk in addition to instant noodles (fruits [1,10], vegetables [1,10], milk and dairy products [11], high-fat fish [1,12], high-fat and processed meats [1,13], sweets and confectionery [1,14], and carbonated beverages [1,15]), which was divided into nine frequency categories: barely eat, once/month, 2–3 times/month, 1–2 times/week, 3–4 times/week, 5–6 times/week, once/day, twice/day, and 3 times/day. Those food groups were fruits, vegetables (except Kimchi), milk and dairy products (yogurt/cheese, etc.), high-fat fish (mackerel/sardines/tuna/herring/salmon, etc.), high-fat and processed meats (fresh bacon/beef ribs/charcoal grilled meat/tripe/ham/sausage/bacon), instant noodle/cup noodle, sweets and confectionery (cakes/cookie/pies/candies/chocolates), and carbonated beverages (coke/sprite/soft drinks/fruit-flavored drinks except 100% fruit juice). In this study, the consumption of these foods as well as instant noodle was divided into 4 categories (≤ 1 time/month, 2–3 times/month, 1–2 times/week, and ≥ 3 times/week) according to frequency distribution.