# Reduction of insulin resistance in 14–15-year-old students after the COVID-19 pandemic: a prospective study from Tsunan, Japan

## TL;DR

This study found that insulin resistance in Japanese teenagers increased during the pandemic but returned to pre-pandemic levels by 2023, while BMI and obesity remained stable.

## Contribution

The study provides evidence that lifestyle changes during the pandemic temporarily increased insulin resistance in adolescents, independent of obesity.

## Key findings

- Insulin resistance (HOMA-IR) increased significantly during 2020–2022 but returned to pre-pandemic levels by 2023.
- BMI and obesity levels remained stable over the 10-year study period.
- The pandemic-related lifestyle changes affected insulin resistance independently of obesity status.

## Abstract

A significant increase in HOMA-IR values has been reported in children after the COVID-19 pandemic. This study aimed to investigate how the changes of HOMA-IR after COVID-19 was post-pandemic (2023–2024).

The study included 462 students aged 14–15 from Tsunan Town, Japan, who underwent health examinations between 2015 and 2024 (258 boys, 204 girls). The students’ HOMA-IR, BMI, and obesity levels were studied, and temporal changes were assessed using the Kruskal-Wallis test. IR was defined as HOMA-IR ≥2.5 and temporal changes were assessed using the chi-square test.

A significant change in the median HOMA-IR was observed over the 10-year period (p < 0.001). The proportion of IR was significantly higher in 2020, 2021, and 2022 (p < 0.001). Conversely, no significant differences were observed in the median BMI and obesity levels over the 10-year period (p = 0.18, p = 0.13). Significant correlations were observed between HOMA-IR and BMI as well as obesity levels throughout the entire observation period and from 2015 to 2019. However, no significant correlations were observed in the years 2020–2024.

The significant increase in HOMA-IR observed after 2020 significantly decreased to values similar to pre-COVID-19 levels by 2023. However, BMI and obesity levels showed no temporal changes. Our findings suggest that changes in lifestyle due to the COVID-19 pandemic during 2020–2022 may have influenced IR in 14–15-year-old students, irrespective of obesity status.