New research from Stanford Medicine provides the first molecular understanding of why people gain weight due to chronic stress. A healthy persons level of glucocorticoids rises and falls in a circadian 24-hour cycle. Peaking around 8 a.m, dropping to its lowest around 3 a.m, and rising back 5 hours later. These rises tell our bodies it is time to get moving and turn on our appetites. The glucose levels in our bloodstream are increased by stress. Short spikes are induced by short term stresses, such as exercise, where as sustained levels are caused by chronic stress. It has long been known that glucocorticoids trigger precursor cells to convert to fat cells. Under normal conditions less than 1 percent of persons precursor cells are converted into fat cells. This normal conversion is essential for only replacing the damaged mature cells and renewing and maintaining healthy at tissue. Therefore, the question at hand for researchers was "what stops normal, healthy, daily increases due to circadian rhythms and healthy short- term stresses from causing all of our precursor levels to convert into fat cells?" Through experiments and computer modeling from mice, it was found that the loss of the normal circadian rhythm for glucocorticoids led to the doubling of the animals fat mass. In regards to the implications of controlling weight gain in humans, as long as stresses occur only during the day, you won't gain weight. However, if you experience chromic or continuous stresses at night, this will result in the loss or normal circadian levels and therefore significant weight gain.
Link to article: https://www.sciencedaily.com/releases/2018/04/180404093920.htm
Link of original published study; http://www.cell.com/cell-metabolism/fulltext/S1550-4131(18)30190-6