Sex Differences in the Effects of Mental Work and Moderate-Intensity Physical Activity on Energy Intake in Young Adults

The aim of this study was to examine the acute effects of mental work and moderate-intensity physical activity on various components of energy balance in young and healthy adults. With the use of a randomized crossover design, 35 participants aged 24 ± 3 years completed three 45-min conditions, namely, (i) resting in a sitting position (control), (ii) reading and writing (mental work (MW)), and (iii) exercising on a treadmill at 40% of peak oxygen uptake (exercise), followed by an ad libitum lunch. The endpoints were spontaneous energy intake (EI), energy expenditure (EE), appetite sensations, and EI for the remainder of the day. We observed that the energy cost of the control and MW conditions was about the same whereas the exercise condition increased EE to a greater extent in men than women. Exercise induced a decrease in EI relative to EE compared to the control condition that was more pronounced in men than women. However, women tended to increase their energy intake after the MW condition compared to the control one whereas an opposite trend was observed in men. None of the appetite sensation markers differed significantly between both sexes. In conclusion, men and women have specific food intake patterns when submitted to cognitive and physical stimuli. 1. Introduction The obesity epidemic that has been described by the World Health Organization (WHO) [1] is more prevalent in women than in men [2]. Despite this greater proneness of women to accumulate body fat when exposed to an obesogenic environment, women are less affected by obesity comorbidities because of difference in fat distribution. Specifically, their predisposition to accumulate an excess body fat in the gluteo-femoral area as opposed to the abdominal area for men has frequently been proposed as less detrimental for health or even, in some cases, as a protective storage strategy [3]. The study of potential sex differences has also been performed regarding the response of energy balance to different lifestyle modalities. For instance, it has been established several decades ago that body weight changes induced by exercise training are more pronounced in male than in female rats [4, 5]. In humans, our research team obtained concordant results by demonstrating a significant weight loss induced by exercise training in men whereas no significant changes were found in women [6]. In addition, preprandial caffeine consumption resulted in a significant decrease in ad libitum energy intake in men but not in women [7]. More recently, the response of energy compensation to vigorous physical