Would that be bad if you're trying to lose weight? The short answer: it depends.
Not all calories, of course, are created equal.
Eating late at night any carbohydrates or foods with processed/added sugars, or drinking alcohol or fruit juices, or even fruit itself, is not recommended if you're trying to lose weight. All carbohydrates, even the more slow-burning ones, say like wild rice, will eventually metabolize into sugars. Unless you're going for a 5-mile walk in the middle of the night, those carbohydrates/sugars, will be stored as bodyfat for future energy use.
Ideally, if you are trying to lose weight, you should go at least 12-14 hours fasting every day. That means, say you finish eating dinner at 8 p.m., you shouldn't eat breakfast until at least 8 a.m. the next morning. Everybody's biochemistry is different, so if you only go 11 hours, that's close enough, but as a general guideline, your weight loss efforts will be more rewarded by not eating late at night and going at least 12 hours from dinner to breaking the fast.
But say you've been particularly active one day; you've burned way more calories that you usually do. Or maybe you're undergoing more stress than normal. In times of stress or increased physical activity, you need to supply your body with more calories. Again, not all calories are created equal, so you need to feed your body healthy calories.
So, on this hypothetical day, in which you've run (or walked) a 10k for charity, and now, at night, "Downton Abbey" has just concluded, and before you call it a night, you want to reward yourself with a snack, will you not lose weight if you eat late at night?
First ask yourself if you're really feeling hungry, or, are you just bored, or being triggered by habit or an emotional reaction....
Drink 2 glasses of water with a squeeze of fresh lemon (but make sure you go to the bathroom one more time than normal before lying down to sleep, so you don't have to go in the middle of the night). You may be surprised that your hunger goes away. If you adopt this strategy, and use it often, you'll manage to overcome hunger; your weight loss goals will be achieved sooner.
But if you must, must, absolutely cave in and eat something late at night, eat something slightly filling that's low in calories and carbs.
A perfect late night snack would be leftover Miracle Noodles. Most Miracle Noodles and Rice have zero net calories. If you eat these late at night with a low-calorie, non-sugar sauce, or just a tablespoon of olive oil and some green veggies like broccoli or spinach, you won't overload your liver with stored glycogen (blood sugar).
Other ideas for late night snacks would be anything higher in protein, such as a slice of lean turkey breast.
But remember, try not to give in to late night cravings. Perhaps if you're starving late at night, you either didn't eat enough at lunch or dinner, or had too many quick-burning carbs like mashed potatoes. If you eat foods that burn fuel too quick, your stomach will want to be refilled.
Remember: refill first with water, wait a few minutes and see if you can't trick that late night hunger craving.