Objective Food Intake in Night and Day Shift Workers: A Laboratory Study

Night shift work is associated with risk of overweight and obesity. In night shift workers, short sleep duration combined with circadian misalignment may contribute to altered food intake regulation, favoring positive energy balance and weight gain. Prior work investigating food intake in shift workers has suffered methodologically due to reliance on subjective self-report for dietary assessment. No study has yet been done to examine the impact of night shift work on food intake in real-life shift workers using objective measures. Female day (n = 12) and night (n = 12) shift workers from a hospital setting participated in a laboratory-based objective food intake assessment. Participants entered the laboratory in the fasted state after awakening from the sleep episode following a final work shift, and underwent an ad libitum 14-item test meal buffet to objectively quantify food choice/intake. Sleep duration (measured via wrist-accelerometry) during the sleep episode before laboratory assessment was significantly longer in day vs. night workers (373.9 +/- 127.5 vs. 260.6 +/- 102.9 min, p = 0.03). No significant group difference was observed in calories consumed during the test meal (943.08 +/- 469.55 vs. 878.58 +/- 442.68 kcal, p = 0.74). When expressed as percent of energy consumed, day workers had higher protein consumption vs. night workers (16.03 +/- 5.69 vs. 11.82 +/- 4.05%; p = 0.05). To our knowledge, this is the first laboratory-based behavioral assessment of food choice/intake in actual night and day shift workers. Although not studied here, work by others has linked protein intake to satiety. This may be a potential pathway placing shift workers at risk for overweight and obesity.