Biofrequency-Guided Nutrition in Spanish Adults

Anthropometric data, including current body weight (in kilograms) and height (in centimeters), will be self-reported by participants. These measurements will be used to compute body mass index (BMI), which is calculated by dividing weight in kilograms by the square of height in meters (kg/m²). BMI categories will be defined in accordance with World Health Organization (WHO) standards: BMI < 18.5 ("underweight"), 18.5 ≤ BMI < 24.9 ("normal weight"), 25 ≤ BMI < 29.9 ("overweight"), 30 ≤ BMI < 34.9 ("obesity class I"), 35 ≤ BMI < 39.9 ("obesity class II"), and BMI ≥ 40 ("obesity class III") (Weir \& Jan, 2023). Although self-reported measurements may be susceptible to bias, previous research indicates that self-reported BMI estimates are generally valid in adult populations (Stommel \& Schoenborn, 2009).

Physical activity across work/school, transport, and leisure will be assessed with the validated PAS-2.1S (Valles-Medina et al., 2021). The scale has nine items: six on daily activities (weekday/weekend sleep, sedentary behavior, active physical activity, leisure, commuting) and three on weekly activities. Sleep duration is self-reported; sedentary behavior covers commuting by car/public transport and screen/reading time. The weekly subscale records light (e.g., walking), moderate (e.g., gardening), and vigorous (e.g., running) activities. Activity intensity, based on METs (Ainsworth et al., 2000), includes values such as sleep (0.9), sitting work (1.5), light activity (3.0), and vigorous activity (6.0). Daily work/transport METs are multiplied by five; sleep/leisure by seven. Missing daily hours (<24) are doubled. Total METs from daily and weekly activities yield total energy expenditure.

Adherence to the Mediterranean diet (MedDiet) will be measured using the PREvención con DIeta MEDiterránea (PREDIMED) questionnaire (Martínez-González et al., 2012). Participants will report the frequency or quantity of consumption of 12 core dietary components (e.g., fruits, vegetables, olive oil, nuts) and two related dietary habits. The 14-item tool assigns binary scores (0 or 1) to each component, with total scores ≥9 indicative of high adherence to the MedDiet.

Tobacco use will be assessed with two questions. First, participants will be asked: "Have you ever smoked tobacco in your lifetime?", with response options ranging from (a) never to (g) 30 times or more. Second, adolescents will be asked about current smoking frequency: (a) I do not smoke, (b) less than once a week, (c) more than once a week but not daily, and (d) every day.

Alcohol consumption will be assessed with: "Have you ever consumed alcohol in your lifetime?", offering options: never, once or twice, 3-5, 6-9, 10-19, 20-29, and 30+ times. Additionally, participants will report the frequency of different alcoholic beverages, coded into days per week: never (0), almost never (0.10), monthly (0.25), weekly (1), daily (7). The mean weekly frequency will then be calculated. Based on these data, participants will be classified as non-drinkers (never consumed alcohol), regular drinkers (weekly or more), or irregular drinkers (monthly or less). Binge drinking will be measured by asking: "Have you ever consumed enough alcohol to become intoxicated?", with options: never, once, 2-3, 4-10, and more than 10 times. Excessive consumption will be defined as having become intoxicated on at least one occasion.

Cannabis consumption will be assessed with the question: "Have you ever used cannabis in your lifetime?", using response options: (a) never, (b) once or twice, (c) 3 to 5 times, (d) 6 to 9 times, (e) 10 to 19 times, (f) 20 to 29 times, and (g) 30 times or more.

Depressive symptoms will be measured using the Spanish version of the Beck Depression Inventory-II (BDI-II) (Sanz \& Navarro, 2003). This self-administered instrument consists of 21 items, each with four response options representing increasing severity over the preceding two weeks. Item scores range from 0 to 3, yielding a total score between 0 and 63.

Anxiety symptoms will be evaluated using the Generalized Anxiety Disorder-7 (GAD-7) questionnaire, validated for primary care (Löwe et al., 2008). This instrument contains seven items (Spitzer et al., 2006), assessing symptoms such as nervousness, worry, restlessness, and irritability over the previous 14 days. Items are rated on a four-point Likert scale: never (0 points), several days (1 point), half of the days (2 points), and almost every day (3 points). Total scores range from 0 to 21, with thresholds as follows: no anxiety (0-4 points), mild anxiety symptoms (5-9 points), moderate anxiety symptoms (10-14 points), and severe anxiety symptoms (15-21 points).

Perceived stress will be assessed using the Spanish version of the Perceived Stress Scale-14 (PSS-14) (Remor, 2006; Remor \& Carrobles, 2001). This 14-item instrument utilizes a five-point response scale: never (0 points), almost never (1 point), once in a while (2 points), often (3 points), and very often (4 points). The total score is calculated by reversing the responses for items 4, 5, 6, 7, 9, 10, and 13 using the conversion scale (0=4, 1=3, 2=2, 3=1, 4=0) and then summing the scores of all 14 items. Higher scores reflect greater perceived stress.

Disordered eating behaviors will be evaluated using the Sick, Control, One, Fat, Food (SCOFF) questionnaire, a concise and validated screening instrument designed to identify individuals at risk for eating disorders (Garcia-Campayo et al., 2005). The SCOFF consists of five items that capture core dimensions of disordered eating, including restrictive intake, preoccupation with weight and shape, and compensatory behaviors. Each item requires a binary (yes/no) response, and a score of ≥2 affirmative answers indicate an increased risk for an eating disorder.