Stress, the hormones it releases and the effects of high fat and high sugary foods on the body and mind push people to overeat.
In short term instances stress can actually suppress appetite but when stress ceases to leave, the release of the hormone cortisol can encourage the body’s to overeat, when stress is relieved cortisol levels return to normal but if stress persists then cortisol may stay elevated along with the desire to overeat.
Stress also has a direct result on food choices due to the fact that foods high in sugar and fat reduce activity in some parts of the brain blocking the feeling of stress giving substance to the phrase "comfort foods".
Exercise releases mood boosting toxins and invokes a feeling of accomplishment leading to smarter food choices to combat against undoing the hard work you've put in the studio.
Social Support from friends and family is also a huge tool against stress, feeling like someone is going through the same experience as you provides a sense of security and reduces isolation, try get a training partner or a lunch partner who you share similar goals with to make your journey less daunting.