Associations between energy intake and physical activity in a sample of adolescent females in New Zealand

Background: Physical activity and energy intake are the two most variable components of energy balance and their association with obesity has been studied separately throughout literature. Despite their important role in energy balance, there is limited evidence describing the direct association between physical activity and energy intake. Objective: The purpose of this study was to investigate associations between energy intake and physical activity levels across categories of BMI in adolescent females from the SuNDiAL project. Design: Adolescent females aged 15-18 y were recruited from eight locations around New Zealand to participate in the SuNDiAL project. Physical activity was measured using ActiGraph GT3X+ accelerometers worn on the right hip 24 hours a day for seven days. Energy intake was measured via two 24-hour dietary recalls and adjusted to represent usual intake using MSM. Height and weight were used to calculate BMI, and WHO growth standards were used to calculate z-scores to categorise participants as normal weight, overweight or obese. Results: 34.5% of the sample were classed as overweight or obese with zero participants in the underweight category. Less than 25% of the sample met the physical activity guideline. 26.9% of participants in the healthy weight category met the physical activity guidelines, while only 11.1% of participants in the obese category met the guideline. Energy intake for healthy weight and obese individuals was similar across BMI categories, however the lowest energy intake was observed in those classified as overweight, but who were meeting the physical activity guidelines. There was no evidence of meaningful association between energy intake and physical activity (R2=0.015). Conclusion: No overall association was found between energy intake and physical activity. Small but insignificant associations were found within BMI categories. Some participants in the overweight category were found to be conducting more physical activity and eating less, likely with intentions to lose weight. Given the sample size is not representative of the New Zealand population further research is required to draw stronger conclusions. Regardless, the findings of this study highlight the need for extensive improvements to be made to help increase physical activity in adolescent girls