There are multiple contributing factors that all play a significant role in someone gaining weight. Managing your weight will involve a careful balance of all these factors to ensure that you do not experience a gain in weight.
Diet
Eating an unbalanced diet primarily consisting of high-calorie foods will result in a surplus of calories. The body stores this caloric surplus in fat, as a reserve source of energy it case the body needs it. As most food today is calorie-rich for its serving size, this can lead to a massive surplus of calories, especially if said food is fatty or processed. This can be managed by a diet focusing on healthy food, consumed in manageable portions.
Exercise
Not exercising or moving enough on a daily basis will also contribute to weight gain. Lack of exercise is a significant contributor to weight gain, especially in tandem with a calorie-rich diet. As modern life does not tend to involve prolonged periods of heavy exercise or movement, this will mean that fat that builds up will tend to stay unless significant and constant exercise is undertaken as part of your weight management routine.
Sleep
If you don’t get enough sleep, you may find yourself gaining weight. A lack of sleep results in the overproduction of ghrelin, a hormone that encourages eating. Leptins, another hormone responsible for managing appetite, is produced in smaller quantities if there is a lack of sleep. This combined change to hormone production can result in a stronger desire to eat more food, thus leading to weight gain if not managed correctly.
Environment
Stress levels and access to healthy foods can influence weight. The stress hormone cortisol stimulates fat and carbohydrate metabolism, increasing appetite. An environment lacking in healthy food options will also contribute negatively to weight management goals.