Protein...Probably the easiest macronutrient to understand but possibly the hardest for some people to eat the required daily amount for their goals.
There are 4 calories per 1 gram of protein. Leaner cuts of meat are advisable to keep saturated fat to a minimum. However both plant based and animal protein both have different qualities and you should use a mix of both.
Protein is meat, fish, eggs, and many more animal based products. But lets not forget that there are plant based versions of protein too (more on those sources later).
In a nutshell our bodies use protein to build & repair tissue, muscles, cartilage & skin. They have many other functions which includes making enzymes and hormones.
A really good way to 'diet' (especially if you have a lot to lose) is to go on a high protein diet for a while. But you would need to work out exactly how much protein you need for your goals so it's advisable to get yourself weighted by a professional and find out what your body fat, muscle & visceral fat is which you would then calculate using your height, overall weight, age and goals.
Finding out these variables will give you the edge when it comes to changing your body and you don't have to starve! Protein keeps you fuller for longer and it can actually help with cravings like sugar. Up your protein lessen your cravings.