STRESS AND WEIGHT GAIN
Weight gain is a result of your calorie intake being higher than your calorie expenditure creating a surplus of energy as a result (1), and often stress would not be the first issue to consider when weight gain has become problematic. However, stress can interfere with normal regulation of how our bodies break down food and its transformation into energy otherwise known as metabolism.
Potential Short Term Response
Stress can be defined as a state of threatened homeostasis (2) (balance within the body) causing a chain effect of events and weight is one area that is affected. Nevertheless, acute intense stress is commonly associated with a reduction of food and reduced body weight gain.
Instead of weight gain, weight loss is also a possibility and is generally seen as a short term response to stress. The central stress response system may be part of the reason for short term weight loss, as it stimulates the release of cortisol and also the potential stimulation of the sympathetic nervous system (fight or flight response). The impact of such a response can be the digestive system being suppressed and the reduction of food intake causing a short term response of weight loss (3,4).
However, the association of reduction in food is generally outweighed by actions such as food being used as a coping mechanism thus leading to weight gain (5,6,7).
Weight Gain Response
Chronic stress has higher associations with weight gain especially within western societies (2) and more research would benefit a further understanding of why stress and weight gain effects outweigh its weight loss effects.
Metabolism syndrome otherwise known as insulin resistance syndrome is associated with chronic stress and higher amounts of intra abdominal fat mass (visceral fat), which has been associated with prolonged sympathetic nervous system stimulation (fight or flight response) (2,3,8,9,10). In addition, obesogenic effects may be down to excess glucocorticoids (anti-inflammatory) and stress eating is related to high calorie-dense food or palatable food as a reward response, which may be influenced by cortisol (a steroid hormone that regulates a wide range of processes throughout the body) (7).
Furthermore, signals may act together on the dopaminergic circuits to drive food intake, and the palatability of food seems to overweigh the nutritional value of food leading to choosing more calorie dense options (8). The feel good hormone that is dopamine can be stimulated and released creating a sense of reward.
The importance of sleep is paramount and lack of sleep can be caused by high amounts of stress (11), and a short duration of sleep has been associated with weight gain (12,13). Additionally, a study published in 2012 suggested that the associated sleep and weight weren't clear in adults (14), but the effect of lack of sleep could also contribute to lack of effort and increased lack of activity during the day resulting in a lower amount of calories being expended. In addition, a decrease in leptin levels (a hormone that controls and inhibits hunger) and an increase in ghrelin (a hormone that stimulates appetite) has been shown with individuals with short sleep duration, which could be another contributing factor to weight gain (16).
It can be concluded that stress has an impact on weight gain, however, it must be taken into account the potential different individual effects. There are a high amount of variables that can contribute to stress responses, therefore, blanket statements should not be made to one's weight gain but an assessment of lifestyle factors should be considered.