A large-scale prospective study found that moderate-to-vigorous physical activity may be associated with a lower risk of nonalcoholic fatty liver disease and other liver outcomes, regardless of whether the activity was concentrated on weekends or spread throughout the week.
In the study, published in BMC Medicine, investigators used UK Biobank data to analyze the outcomes of 88,656 participants aged 37 to 73 years without prior liver diseases who wore wrist Axivity AX3 accelerometers on their dominant wrist for 7 days between 2013 and 2015. During a median follow-up of 6.8 years, the investigators observed a nonlinear inverse association between total moderate-to-vigorous physical activity (MVPA) and incident nonalcoholic fatty liver disease (NAFLD), with a threshold of 208 minutes per week. MVPA was defined as awake behavior at ≥ 3 metabolic equivalents of task (METs).
The participants were classified into three groups based on their MVPA patterns:
- Inactive (< 150 min/week)
- Active weekend warrior (≥ 150 min/week with ≥ 50% of total MVPA achieved within 1 to 2 days)
- Active regular (≥ 150 min/week but not meeting weekend warrior criteria).
The primary outcome was incident NAFLD, identified through hospital inpatient data and death register records. Secondary outcomes included incident severe liver diseases, liver cirrhosis, and liver magnetic resonance imaging (MRI)-based steatosis and fibrosis.
Cox proportional hazards models were used to estimate associations between MVPA patterns and outcomes, adjusting for demographics, socioeconomic factors, lifestyle behaviors, and body mass index.
The study population had a mean age of 56.1 years (standard deviation [SD] = 7.8) and 56.7% were female. The mean time spent in MVPA was 290 minutes/week (SD = 242). Among the participants, 33.1% of them were classified as inactive, 41.5% as active weekend warriors, and 25.4% as regularly active.
Among the key findings were:
- Participants achieving ≥ 150 minutes/week of MVPA had a significantly lower risk of incident NAFLD compared with inactive participants, whether activity was concentrated on weekends (hazard ratio [HR] = 0.55, 95% confidence interval [CI] = 0.44–0.67) or spread throughout the week (HR = 0.49, 95% CI = 0.38–0.63).
- Similar protective associations were observed for severe liver diseases, liver cirrhosis, liver steatosis, and fibrosis.
- The risk of NAFLD decreased rapidly with increasing MVPA up to 208 minutes/week (HR per 100 min/week increment = 0.68, 95% CI = 0.57–0.81) and more gradually beyond this threshold (HR = 0.91, 95% CI = 0.84–0.99).
During follow-up, 562 participants developed NAFLD (incidence rate = 10.1 per 10,000 person-years). Both active weekend warriors (HR = 0.55, 95% CI = 0.44–0.67) and regularly active participants (HR = 0.49, 95% CI = 0.38–0.63) had significantly lower risks of incident NAFLD compared with inactive individuals.
Secondary outcomes showed similar protective associations:
- Severe liver diseases (504 cases): weekend warrior HR = 0.75 (95% CI, 0.61-0.93), regular active HR = 0.76 (95% CI = 0.59–0.97)
- Liver cirrhosis (436 cases): weekend warrior HR = 0.80 (95% CI = 0.64–0.99), regular active HR = 0.76 (95% CI = 0.58–0.99)
- Liver steatosis (3,416 cases): weekend warrior odds ratio [OR] = 0.74 (95% CI = 0.67–0.81), regular active OR = 0.60 (95% CI = 0.53–0.67)
- Liver fibrosis (559 cases): weekend warrior OR = 0.62 (95% CI = 0.51–0.76), regular active OR = 0.48 (95% CI = 0.37–0.62).
The compositional data analysis approach showed that time spent in MVPA relative to other movement behaviors (sleep, sedentary behavior, and light physical activity) was associated with a reduction in the risk of incident NAFLD (HR = 0.84, 95% CI = 0.78–0.91, P < .001).
Sensitivity analyses, including alternative definitions of weekend warrior patterns (≥ 50% of total MVPA over 1 to 2 consecutive days or 1 to 2 weekend days) and exclusion of participants within 2 years of follow-up, yielded consistent results. The findings also remained stable after adjusting for preexisting hypertension, diabetes, and healthy diet scores.
Stratified analyses showed no significant interactions between MVPA patterns and age, sex, body mass index, smoking status, or alcohol consumption on the risk of incident NAFLD (all P for interaction > .05).
Limitations of the study included potential selection bias because of the low response rate in the UK Biobank, predominance of participants of European descent, and possible underestimation of mild NAFLD cases. Additionally, the 7-day monitoring period may not have fully captured long-term physical activity habits.
The authors declared that they have no competing interests.