Eating at night is not really a problem as long as you choose foods that are good for you, and you stay within your daily calorie need. In fact, eating a small, but carbohydrate-rich snack may help you sleep better at night (or even better - have some cherries that contain melatonin). Eating at night becomes a more of a problem if you overeat or choose foods that are high in calories, fat, sodium or sugar.
Sometimes eating at night is a scheduled thing. People who work in the afternoons or evenings may eat breakfast late at night and have dinner in the morning.
Perhaps the idea that eating after a certain time of day comes from fad diets, or perhaps it stems from concerns about night-eating syndrome (sleep eating disorder). People with night-eating syndrome consume at least 25 to 50 percent of their daily calories after their regular dinnertime, almost every night.
Night-eating syndrome patients also tend to also suffer from depression, low self-esteem and obesity. If you find that you eat most of your calories at night and you have diabetes or weight related problems, or feel depressed, you need to speak to your health care provider.
Morse SA, Ciechanowski PS, Katon WJ, Hirsch IB. "Isn't this just bedtime snacking? The potential adverse effects of night-eating symptoms on treatment adherence and outcomes in patients with diabetes." Diabetes Care. 2006 Aug;29(8):1800-4.
Gluck ME, Geliebter A, Satov T. "Night eating syndrome is associated with depression, low self-esteem, reduced daytime hunger, and less weight loss in obese outpatients." Obes Res. 2001 Apr;9(4):264-7.