Why use protein shakes

What he said ^^.. Although protein shake is a bit more easily recordable than whole foods. It's processed and comes with a measuring scoop. It's easy and accurate to log, whereas meats have sodium + different ways to prepare (added fats)+ different weights + different fat content of the meat itself.

I am pretty knowledgeable about nutrition, calories, exercise and all the basics- but I am really curious about what the advantage is to using a protein shake? When I hit a stand still in my weight loss a month or so ago, my trainer told me to try substituting a protein shake in place of a meal and that might shake things loose. Does it help with weight loss? Is it better for muscle building? Is there an ideal time to have one? Do you use them in place of a meal or in addtiion to?

Just trying to learn.

In addition to the above replies, I would ask your trainer WHY he or she made that suggestion. The only way this would work would be if the shake reduces your calorie intake because it is lower in calories than the meal you were eating in it's place, and even if that IS the case, it could still be a poor suggestion.

Without him or her knowing what meal you are replacing and moreover without knowledge of what the rest of your meals are (context matters), it's a very arbitrary suggestion that should cause you concern over your trainer's ability.

I've tried different kinds and they all make me feel sick so no shakes for me

Protein shakes are often used to assist with weight loss. One of the major benefits of protein is it makes you feel full, and therefore helps to curb appetite. There are hundreds of different types of protein shakes though, all of which have a different function.
There are meal replacement powders (MRP's) that have more calories and are fortified with different vitamins and minerals and are essentially designed to take the place of a meal, while also providing protein to help you feel full and to help your muscles repair themselves.

There are diet "protein" shakes (i.e. slimfast etc). These are low calorie, but really don't provide much actual protein. They are mostly just nutrients to help you skip actual meals.

Then there are your Whey's, which are typically used by people working out to help quickly repair your muscles after a workout. Taking Whey in place of a meal is not really what it was designed for. It is typically fairly low calorie and packed with protein. Of course I am a complete hypocrite because I do occasionally grab a whey shake on my way out the door in the morning when I don't have time for breakfast, but I certainly wouldn't suggest doing that on a regular basis.

I use Vega shakes to increase my nutrients and protein. I am a vegetarian so I find that it is a good way to make sure that I am getting all of the things that I need in me. Although they taste pretty nasty!