BACKGROUND There is currently no information on the lifetime diet of ultra-endurance exercisers. This study describes changes in diet across the lifetime of current ultra-endurance exercisers and the relationship between diet and physical activity (specifically ultra-endurance exercise [UEE]). METHODS Lifetime physical activity and diet were assessed in current ultra-endurance exercisers (N.=120; ages 21-74 years) over six life periods (5-12, 13-18, 19-30, 31-45, 46-60, 61-75 years). Using the life period having the largest absolute increase in UEE (IUEE), diet was assessed according to food category scores and dietary patterns. Changes in lifetime diet were described by comparing food category scores between adjacent life periods. Differences in food category scores were investigated between the life period for each IUEE group and the preceding life period and associations between dietary patterns and UEE were investigated within each IUEE group. Relationships between lifetime diet and UEE were investigated by examining associations between lifetime food category scores and lifetime UEE. RESULTS The participant group had significant increases in all food category scores from 13-18 to 19-30 years and significant decreases in all food category scores from 19-30 to 31-45 years. UEE correlated negatively with the Western style dietary pattern in the IUEE19-30 group and positively with the fruit and vegetable dietary pattern in the IUEE31-45 group. There was a positive correlation between lifetime UEE and lifetime vegetables and fruit category scores. CONCLUSIONS The ultra-endurance exercisers in this study exhibited changes in diet similar to general populations, which appear to reflect typical nutritional requirements across the lifespan.