Caloric and Macronutrient Intake Differ with Circadian Phase and between Lean and Overweight Young Adults

The timing of caloric intake is a risk factor for excess weight and disease. Growing evidence suggests, however, that the impact of caloric consumption on metabolic health depends on its circadian phase, not clock hour. The objective of the current study was to identify how individuals consume calories and macronutrients relative to circadian phase in real-world settings. Young adults (n = 106; aged 19 +/- 1 years; 45 females) photographically recorded the timing and content of all calories for seven consecutive days using a smartphone application during a 30-day study. Circadian phase was determined from in-laboratory assessment of dim-light melatonin onset (DLMO). Meals were assigned a circadian phase relative to each participant's DLMO (0 degrees, similar to 23:17 h) and binned into 60 degrees bins. Lean (n = 68; 15 females) and non-lean (n = 38, 30 females) body composition was determined via bioelectrical impedance. The DLMO time range was similar to 10 h, allowing separation of clock time and circadian phase. Eating occurred at all circadian phases, with significant circadian rhythmicity (p < 0.0001) and highest caloric intake at similar to 300 degrees (similar to 1900 h). The non-lean group ate 8% more of their daily calories at an evening circadian phase (300 degrees) than the lean group (p = 0.007). Consumption of carbohydrates and proteins followed circadian patterns (p < 0.0001) and non-lean participants ate 13% more carbohydrates at 240 degrees (similar to 1500 h) than the lean group (p = 0.004). There were no significant differences when caloric intake was referenced to local clock time or sleep onset time (p > 0.05). Interventions targeting the circadian timing of calories and macronutrients for weight management should be tested.