Daily calorie intake requirements vary according to gender and weight, but an average-weight male who engages in moderate physical activity regularly needs approximately 2,500 calories per day. An average-weight woman needs around 2,000 calories per day. As you can see, 500 calories per meal--or 1,500 calories a day--falls well below the average, so while 500-calorie meals are effective for losing weight in the short term, you may not want to cut calories any more than this, as you can wind up depriving yourself of basic nutrients.
The Better Bodz website has posted a clear, handy chart, detailing a variety of meal ideas that fall between 450 and 500 calories. Meat eaters can find satisfaction in the steak and broccoli meal: 8.3 oz. of sirloin steak (not cooked in butter), paired with a 2 cup serving of fresh steamed broccoli. For fish lovers, a grilled or poached 10 oz. salmon fillet, served with a 6 oz. baked sweet potato, is loaded with vitamins and healthy omega-3 oils, while remaining at the 500 calorie mark.
Asian and Indian meals are a reliable way of eating well and keeping calorie counts down, as many Asian and Indian meals avoid heavy cream and butters, with a few exceptions in the realm of Indian cuisine (i.e., paneer cheese and korma sauces). Wegmans provides a recipe for Shanghai stir-fry tofu with sesame seeds that's spicy and full of flavor (though you'll want to replace the oyster sauce with vegetarian oyster sauce).
Chana masala, an Indian spiced chickpea dish, is also spicy yet warm and comforting. Serve it over a single serving of basmati rice, and sprinkle a generous amount of fresh chopped cilantro over the entree before serving. This meal, besides being low-calorie and healthy, is also extremely cheap to put together.
Fast food places are generally awful and unhealthy places to get your food, but for those who insist on getting their convenience-food fix while counting calories, there are a few somewhat decent meals to be had. The website Eat This, Not That is a treasure trove of healthy eating info; one of the site's recommendations is a grilled chicken sandwich with a medium iced tea, and a side salad drizzled with balsamic dressing. Hard as it may be to believe, there are even low-calorie, low-cholesterol options at franchised at donut eateries: look for egg whites on English muffins (rather than bagels), accompanied by an English breakfast tea.