Most people change their eating habits based on the mood they are in. Many eat more when stressed, when they are bored, or when they have company. Some react the other way around, losing weight when stressing out or eating less when in a party. In general, feelings of euphoria make us less hungry, while less enthusiastic times see cravings and compulsive eating increase.
You can see this play out in a great many different places. Are you one of those that gain weight in the winter and shed it in the summer? Then your mood probably reacts to changes in the amount of sunlight you are getting. People whose mood is affected by the seasons have Seasonal Affective Disorder, something you should think about when considering a diet.
Many people have starter syndrome: they experience a sudden drop in weight in the first week of a diet, and then things go slowly. While that’s mostly because the body can shed a few pounds easily, but then puts up a fight against any further reduction, a part of this behavior is readily explained by the sense of euphoria that comes with the start of a diet. As you plateau, the euphoria gives way to the diet blues, which in turn get the cravings started for good.
Another example is the sleepless circle. When you can’t sleep at night, your mood tends to go down. You can manage fine during most of the day, but when it comes to the evening and night, you overeat to mask your tiredness. Eating food late, especially sugars and salts, worsens your sleep. You end up causing your own tiredness, and making it worse.
A reverse example of mood favoring weight loss is the exercise boost. When you exercise, you do three things at the same time: (1) you burn calories, (2) you increase your muscle mass and heart rate, both of which burn calories long after the workout, and (3) you cause your mood to improve, reducing cravings.