Limited literature exists on healthy lifestyle promotion for older adolescents (16–18-year-olds), yet this is a life stage when habitual healthy lifestyles could be developed ^{(Reference Viner and Macfarlane1)}. A total of 93 participants (39 males; 54 females) (mean age = 16.9 (SD 0.4) years), from three low socio-economic secondary schools in England, completed an online version of the Short Form Food Frequency Questionnaire (SFFFQ) ^{(Reference Cleghorn and Cade2)} in order to measure diet quality. Additional questions focused on their perceived healthiness and how they felt healthy lifestyles were promoted to them. The SFFFQ questionnaire responses for the frequencies of each 20 food items were grouped within the Diet and Nutrition Tool for Evaluation (DANTE) excel spreadsheet according to the 5 food groups (fruit, vegetable, oily fish, fat, non-milk extrinsic sugars (NMES)). The recommended food group score for fruit, vegetables and oily fish was 3 and the recommended score for fat and NMES was 1. The food group scores were then added together to generate an overall diet quality score (DQS). A low DQS (ranging from 5–10) represented a poor dietary intake; a range between 12–15 represented an adequate dietary intake and a DQS of 11 reflected an optimum dietary intake ^{(Reference Cleghorn and Cade2)}. Perceived healthiness was predicted by participants’ rating their overall health on a 5-point scale (excellent, very good, good, fair or poor) over the past 12 months. A multi- variance of statistical analysis was undertaken within SPSS 24.0 statistical analysis (IBM Corp, Armok, NY, USA) to assess the participants’ food group scores and DQS according to sex and perceived healthiness.

Statistical significance was set at <0.05 ± one standard deviation. Qualitative open-ended questions were analysed via thematic analysis ^{(Reference Cooper, Camic and Long3)}. Participants overall DQS was low (9 (±1.96): males = 9.36 (±1.97), females = 9.12 (±2.01)). There were significant interactions between sex, perceived healthiness levels and fat scores (F = 2.532, p = 0.048). The data indicates that among males, those who rated themselves as having poor health had eaten the recommended intakes of fat (1.00 ± 0.00). This is in comparison to females who rated themselves as having poor health but ate more than the recommended intakes of fat (2.60 ± 0.89). Most (90%; n = 80) participants did not report school as a place that promoted healthy lifestyles. It is recommended as a public health measure and as an educational policy matter that schools implement more targeted healthy eating initiatives for older adolescents. Further, gaining a deeper insight into male older adolescents’ health literacy is needed to ensure they fully understand, appraise and use information to make decisions about their health now that will benefit them as they transition into adulthood ⁽⁴⁾.