# Concurrent Changes in Diet Quality and Physical Activity and Association With Adiposity in Adults

## TL;DR

Improving diet and physical activity together leads to the most significant reduction in body fat and belly fat in adults.

## Contribution

The study shows that combined improvements in diet and physical activity have greater benefits for reducing adiposity than either alone.

## Key findings

- Improvements in diet and physical activity were independently linked to less body fat and visceral fat gain.
- Combined improvements in both behaviors led to the greatest reduction in visceral fat.
- The benefits were stronger in people who were overweight or inactive at the start.

## Abstract

This cohort study investigates independent and joint associations of changes in diet quality and physical activity with body composition indices among adults in the UK.

Are there independent and joint associations of changes in diet quality and physical activity with changes in adiposity?

In this cohort study of 7256 UK adults, improvements in diet quality and physical activity were independently associated with a lesser increase in total body fat and visceral fat, with the greatest benefit observed when both health behaviors improved together. The finding for visceral fat persisted after adjusting for total body fat, and no compensatory or synergistic interaction was found.

These findings suggest that improving diet quality and physical activity over time may be most effective for managing overall and central adiposity and achieving a healthier adiposity profile.

Diet and physical activity (PA) are both associated with body weight, but less is understood about how long-term changes in these behaviors may be associated with changes in adiposity in the general population.

To evaluate associations of concurrent changes in diet quality and PA with different body composition indices.

This cohort study was conducted among participants in the UK population-based Fenland study, with repeated measurements of health behaviors and adiposity. Data collection occurred in 2005 to 2015 and 2014 to 2020, with a mean (SD) follow-up of 7.2 (2.0) years. Data were analyzed from January 2024 through April 2025.

Mediterranean diet score (MDS), a measure of adherence to the Mediterranean diet (range, 0-15 points), was assessed with a food frequency questionnaire. PA energy expenditure (PAEE), measured in kilojoules per kilogram per day, was assessed and calibrated with heart rate and movement sensing. Change variables were derived.

Indices of total adiposity (weight, body mass index and body fat) and regional adiposity (waist circumference, visceral adipose tissue [VAT], and subcutaneous adipose tissue) were assessed with anthropometry and dual-energy x-ray absorptiometry. Hepatic steatosis was ascertained by abdominal ultrasonography.

The analysis included 7256 participants (mean [SD; range] age at recruitment, 48.8 [7.4; 29-65] years; 3748 female [51.7%]). In multivariable linear regression models after adjustment for potential confounders and baseline values, changes in both exposures were negatively associated with changes in all adiposity indices. For example, each 1-SD (1.27 points) increase in the change in MDS was negatively associated with changes in adiposity measures (change in body fat: β = −0.47 kg; 95% CI, −0.58 to −0.36 kg; change in VAT: β = −45 g; 95% CI, −55 to −35 g), and each 1-SD (19.0 kJ/kg/d) in the change in PAEE was similarly negatively associated with changes in adiposity measures (change in body fat: β = −1.40 kg; 95% CI, −1.51 to −1.26 kg; change in VAT: β = −108 g; 95% CI, −118 to −98 g) . Despite no evidence for a diet-PA interaction, simultaneous increases in MDS and PAEE were associated with a greater magnitude of decrease in adiposity, with a β of −149 g (95% CI, −187 to −111 g) for change in VAT among participants in higher joint change in MDS and change in PAEE tertiles. Associations had higher β values among individuals with overweight or obesity or who were physically inactive at baseline; for example, for each 1-SD increase in the change in PAEE, the β for change in body fat was −0.96 kg (95% CI, −1.10 to −0.81 kg) when baseline BMI was less than 25 and −1.74 kg (95% CI, −1.91 to −1.57 kg) when baseline BMI was 25 or greater (P for interaction < .001).

In this study, improved diet quality and increased PA were independently associated with weight loss or less weight gain and a healthier adiposity profile. Combining these health behaviors was associated with the greatest adiposity-related benefits.