Glycemic instability and spontaneous energy intake : association with knowledge-based work

Abstract

Objective: To further document the impact of knowledge-based work (KBW) on spontaneous energy intake and glucose homeostasis. Methods: We used a within-subjects experimental design, in which each participant was engaged in each of the three 45-minute conditions followed by an ad libitum buffet, 1) resting in a sitting position; 2) reading a document and writing a summary; or 3) performing a battery of computerized tests. Fourteen female students (mean age: 22.8 2.3 years, mean body mass index: 22.4 2.5 kg/m2 ) were recruited to participate. Plasma glucose, insulin, and cortisol levels at seven time-points, and appetite sensation markers were measured at each experimental condition. Results: The mean ad libitum energy intake after the reading-writing and the automated test-battery conditions exceeded that measured after rest by 848 kJ and 1057 kJ, respectively (p .05). No specific dietary preference was detected, as reflected by the comparable percent of energy from each macronutrient in the three conditions. No significant difference in appetite sensation markers was observed among the three conditions. Mean cortisol level over 45 minutes in the two KBW conditions was significantly higher (p .05) compared with the control condition. Finally, a significant increase in variations in plasma glucose and insulin levels was observed as compared with the control condition (p .01). Conclusions: This study showed that KBW acutely induces an increase in spontaneous energy intake, and promotes an increased fluctuation in plasma glucose and insulin levels. This study contributes to the documentation of a new risk factor for a positive energy balance, with the potential to lead to overweight in the long-term. Key words: mental work, cognitive tasks, energy balance, appetite, stress, sedentarity.