the key is not to rob yourself of calories. you'll want to consume 300 calories less than your resting metabolic rate (the amount of calories your body uses daily). Divide that by 5 and that's about the number of calories you need at each meal. (you'll need 5 meals a day, about every 2-3 hours to keep your metabolism going strong). Also, try to eat your breakfast no later than 30 mins after you wake up. This will kick start your metabolism for the day.
The key is having enough protein and fiber to keep you fuller longer.
Average woman needs 100-120 grams of protein each day. you need to feed your muscles so you can burn more fat. otherwise your body will burn your muscle when you lose weight.
Also, once you reach your goal, you can add those 300 calories back to maintain it. same thing for gaining weight (which i know you don't want to do here, just saying..) add 300 calories to your resting metabolic rate.
And a biggy, try not to have refined carbs (pasta, rice, bread, etc.) with dinner. complex carbs are fine though, which are mostly vegetables.
I try to have a big carby lunch, then just a small dinner, usually 3-6 oz of meat with however much steamed veggies I want, and if i'm hungry enough, a salad too.
Some good snacks are:
-cottage cheese
-greek yogurt
-nuts
-any vegetable
-any fruit
crackers and chips aren't so good snackwise.
Also, be sure to get plenty of water. Divide your weight in half, and that's how much water in oz.'s your body needs.
Watch out for sodium levels, and sugar.
Go for lean meat when you can, (chicken, turkey, fish..)
Since you're vegetarian, tofu, beans, and dairy should work for you. vegetables also have some protein in them too. if you don't consume dairy either, then look online or at books about good sources of protein for vegans.
Just doing that without killing yourself at the gym should give you some good results.
I hope this helps! I've taken nutrition classes and am a wellness coach now, so I really love helping people on this subject!
you can do it!