2) Health-related behavioral variables
The frequency of breakfast consumption was assessed with the question, “During the past 7 days, how many days did you eat breakfast?” with allowed responses of “never, 1, 2, 3, 4, 5, 6, or 7 days.” Those who indicated eating breakfast less than 2 days per week were called “breakfast skippers” according to the standards set in the survey. The frequency of vigorous exercise in the preceding 7 days, which was accompanied by very fast breathing or sweating, and by >20 minutes of activity was also assessed. Vigorous exercise was classified into none, occasional (1–3 days), and frequent (more than 4 days per week). Participants were considered to be current smokers if they answered “more than 1 day over the past month” to the question “Do you smoke?” For alcohol consumption status, the current drinker was indicated by a reply of “more than 1 day over the past month” to the question ‘Do you drink alcohol?” in the standpoint of survey.