# Body mass index, physical activity, and severe periodontitis– a cross-sectional HUNT4 Oral Health Study

## TL;DR

This study found that obesity and low physical activity are linked to more severe periodontitis in Norwegian adults.

## Contribution

The study explores how BMI and physical activity levels together influence periodontitis severity.

## Key findings

- Obesity was associated with severe periodontitis.
- Moderate physical activity showed an inverse association with periodontitis severity.
- Physically inactive individuals with overweight or obesity had higher prevalence of severe periodontitis.

## Abstract

The association between body mass index (BMI), physical activity (PA), and periodontitis remains unclear, particularly how BMI combined with activity levels affects periodontitis. This study aimed to assess the associations between BMI, its combination with PA, and periodontitis severity in Norwegian adults.

This cross-sectional study included data from participants aged ≥ 20 from the Norwegian HUNT4 Oral Health Survey (2017─2019) (N = 4,384). BMI (kg/m2) was categorized as normal weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2), and obesity (≥ 30 kg/m2). The PA score was constructed based on frequency, duration, and intensity (inactive/low, moderate, high). The combination of BMI and PA was classified into four groups: (1) normal weight, active; (2) normal weight, inactive; (3) with overweight-obesity, active; and (4) with overweight-obesity, inactive. The outcome was periodontitis severity (stages), categorized based on the 2017 Classification of Periodontal and Peri-Implant Diseases and Conditions. Prevalence ratios with 95% confidence intervals were calculated using modified Poisson regression accounting for potential confounders.

Obesity was associated with severe periodontitis, whereas moderate PA showed an inverse association. Individuals with overweight or obesity who were physically inactive had a higher prevalence of severe periodontitis compared to individuals who were normal weight and physi­cally active.

These findings suggest that individuals with obesity and low PA are associated with increased periodontitis severity. Further studies are needed to confirm these associations. This cross-sectional study suggests that physical activity may help mitigate the adverse impact of obesity on periodontitis severity, highlighting the need for longitudinal research and supporting the integration of PA recommendations into oral health management strategies.

The online version contains supplementary material available at 10.1186/s12903-026-07882-x.