AbstractIrregular breakfast consumption and food timing patterns in relation to weight status and inflammation were investigated in a cross-sectional manner among 644 participants in the Cancer Prevention Study-3 Diet Assessment Sub-study. Breakfast consumption, and the individual means and the intra-individual standard deviation (isd) of time at first intake of the day, duration of daily intake window and midpoint of daily intake window were collected via six 24-h recalls and examined in relation to BMI, waist circumference (WC) and inflammation (glycoprotein acetyl (GlycA)). Compared with consuming breakfast on all six recalls, linear regression models showed those who consumed breakfast on 4 or 5 of the days had a 1·29 (95 % CI 0·19, 2·38) and 1·64 (95 % CI 0·12, 3·16) kg/m² higher BMI; no association was found for consuming breakfast ≤3 d. At 1 h later, the average time of first intake was associated with a 0·44 (95 % CI 0·04, 0·84) kg/m² higher BMI. A 1-h increase in the isd of first intake was associated with a 1·12 (95 % CI 0·49, 1·75) kg/m² higher BMI; isd in duration and midpoint of intake window were significant prior to additional adjustment for isd in the first intake. One-hour increases in isd for the first intake time (β: 0·15; 95 % CI 0·04, 0·26) and the midpoint of intake window (β: 0·16; 95 % CI 0·02, 0·31) were associated with higher GlycA. No associations were observed for WC independent of BMI. The results provide evidence that irregularity in breakfast consumption and daily intake timing patterns, particularly early in the day, may be related to weight status and inflammation.