To explore gender-specific variations related to activity intensity in the relationship between physical activity (PA) and mental health (MH). Evaluating whether psychological well-being enhances with increases in PA at recommended levels and above, in the general population.

Cross-sectional.

Population-based, representative for Belgium.

A total of 6803 adults aged 25–64 years from the Belgian National Health Interview Survey.

Multiple logistic regression analyses showed that clearly different intensity levels characterised the PA that associated with MH in women and men. In men, inverse associations existed between participation in vigorous-intensity PA and feelings of depression (OR = 0·580; 95 % CI 0·405, 0·830), anxiety (OR = 0·547; 95 % CI 0·364, 0·821) and symptoms of somatisation (OR = 0·590; 95 % CI 0·398, 0·874). In women, positive associations existed between walking and emotional well-being (OR = 1·202; 95 % CI 1·038, 1·394) and inverse associations between participation in moderate-intensity PA and symptoms of somatisation (OR = 0·737; 95 % CI 0·556, 0·977). Secondary analyses confirmed that differences in psychological complaints were significant for vigorous PA in men, and for moderate PA in women, whereas differences in emotional well-being were significant for walking exclusively in women.

In the general population, the PA–MH relationship is always positive, regardless of activity intensity. In men, it addresses complaints (symptoms, palpable discomfort) and the optimal PA intensity is high. In women, it addresses complaints, but also distress (lowered mood, disturbing anxiety, altered well-being) and the PA intensity is mild.