First of all, you should never skip meals! It's bad for your stomach, bad for your blood sugar and makes you feel really bad.
When you skip meals, you feel lousy because food gives us energy (particularly when we eat the right kinds of foods). Because you have missed meals, you may faint, feel nauseous or dizzy or overeat at the next meal.
What you need to do is find out what your RMR (Resting Metabolic Rate) is. Your RMR is the amount of calories your body burns at rest, for example, when you are sleeping. It is also the number of calories that your body needs to maintain your present weight.
If, for example, your RMR is 1400, then you would need to eat approximately that number of calories a day to maintain your weight; if you wanted to gain weight then you would consume more and if you wanted to lose weight, then you would consume less (never less than 1200 calories for a woman and never less than 1500 for a man).
Figure out how many hours you are awake in the day, say for example if you wake up at 6 a.m. and go to bed by 10 p.m. then you are awake for approximately 16 hours. Try to split your meals up so you are having 4-6 smaller meals every 2.5 - 4 hours, i.e. your meals are evenly spaced. Divide the amount of calories you need (in the example I gave, 1400) between those 4-6 meals.
So if you are having four meals a day, then each meal should be around 350 calories; if you're having 6 meals, each should be about 230 calories.
350 calories is a couple slices of whole wheat bread with about 4 ozs. tuna and a small salad (use vinaigrette dressing) or a grilled, baked or roasted chicken breast with a 1/2 cup brown rice and steamed broccoli and a half cup of grapes (or a cup of strawberries or a large orange...you get the picture).
Or it can be 4 ozs. ground turkey (try getting the leaner ground turkey to cut down on fat and calories), a 1/2 cup of spaghetti with a little sauce (use ketchup, vinegar, brown sugar and a little hot pepper sauce instead of the prepackaged sauces on the market) and a fruit.
As you can see just by these three examples, there are options for meals that are tasty, nutritious and yet meet your caloric needs.
Another option is having a meal replacement PROTEIN shake that has good carbs, a good amount of protein and not too much fat or sugars. Try to find one that has at least 10 grams of protein and not more than about 15 grams of carbs. Otherwise you may find that the shake makes you hungrier and that you “crash” because of too much sugar.