Ultra-processed food consumption and obesity in the Australian adult population

Background: Global increases in ultra-processed food sales and obesity have been observed, including in Australia. Prior Australian data showed ultra-processed food intake is associated with nutrient intakes outside recommendations for obesity prevention. This study examined the association between ultra-processed food consumption and obesity among Australian adults, overall and by age group, sex and physical activity level. Methods: Cross-sectional analysis of 7411 adults ≥20 years from the 2011–2012 National Nutrition and Physical Activity Survey. Dietary intake was assessed via 24-h recall and foods classified with NOVA. Anthropometry (BMI, waist circumference (WC)) was measured. Regression models evaluated associations between quintiles of dietary share of ultra-processed foods and obesity indicators, adjusting for socio-demographics, physical activity and smoking. Results: After adjustment, higher dietary share of ultra-processed foods showed significant dose-response associations with greater BMI and WC and higher odds of obesity and abdominal obesity (P-trend ≤ 0.001). Compared with the lowest quintile, the highest quintile had higher BMI (0.97 kg/m²; 95% CI 0.42, 1.51), higher WC (1.92 cm; 95% CI 0.57, 3.27), and greater odds of obesity (OR 1.61; 95% CI 1.27, 2.04) and abdominal obesity (OR 1.38; 95% CI 1.10, 1.72). Trends were similar across age groups, sex, and physical activity level. Conclusion: Ultra-processed food consumption is associated with obesity among Australian adults, supporting its potential role in Australia’s obesity burden.