Well, adequate protein intake will help build muscle and/or prevent muscle loss if you are in a calorie deficit. It controls appetite and staves off hunger better than fats or carbs as it causes you to feel full longer.It also requires more energy than other macros for your body to digest, thus effectively burning more calories gram for gram through the digestion process.
All of these reasons make high-protein diets great for fat loss.
Where do I get it?
Meat, fish, eggs, cheese, beans are all good sources.
How much do I need?
It really depends on your weight, bodyfat % and goals – as low as 0.5 grams per pound of lean body mass (per day) and as high as 1.5-2 grams per pound of lean body mass.
Lean body mass is your total bodyweight minus your fat. For example, if you weigh 200 pounds and are 20% bodyfat, your lean body mass is 160 pounds, or 200 – (200*20%).

So, if you weigh 200 pounds and have 160 pounds of lean body mass, 0.5 grams per day would be 160*0.5 = 80 grams of protein.

What’s it do?

Fat is an essential nutrient that our bodies require to live; it assists in vitamin absorption, hormone regulation, brain function, and more.

Where do I get it?

Meat, fatty fish, avacados and countless other sources.

How much do I need?

Again, it depends on your weight, bodyfat percentage and goal – probably somewhere between 15% and 45% of your total calories. However, it can vary based on your total calories consumed and whether you are in a caloric surplus or deficit. Somewhere between 0.35-0.7g per pound of lean body mass is a good range.

What’s it do?

Carbs are stored in the liver, brain, blood and muscles as glycogen. Our bodies use carbohydrates for energy.

Where do I get it?

Fruit, vegetables, grains, many processed foods/drinks, and seemingly everything you obsessively craved if you’ve ever tried a low-carb diet.

How much do I need?

It depends. Technically, you can live on zero carbs. But, bodybuilders or endurance athletes have consumed 700+ grams per day. So, the range is pretty wide.

0.5-2 grams per pound of lean body mass is probably a decent range, again, depending on activity level, weight, bodyfat percentage and goals.

Remember, all calories come from macronutrients.

Vitamins, minerals, sodium, etc are micro-nutrients and do not contain calories.

ONLY proteins, fats, carbs and  yield calories.

One gram of protein yields 4 calories.

One gram of carbohydrate yields 4 calories.

One gram of fat yields 9 calories.

One gram of alcohol yields 7 calories

Calories provide us with energy, you probably know that. As we discussed earlier, all calories come from proteins, fats, carbs or alcohol.  Micronutrients (vitamins and minerals) do not contain calories.Counting Macros versus Counting Calories

Alright, I get this macro stuff, but can’t I just count calories?

The truth is, yes, you will definitely lose weight if you focus solely on calories and consume fewer cals than you burn. That’s just plain old science. The laws of thermodynamics (calories in – calories out) are for real.

But the quality of your weight loss will suffer if you ignore the macronutrients.

For example, inadequate protein during a calorie deficit will cause you to lose muscle. Inadequate fat intake will negatively impact many of the hormones that help your continued weight loss. And inadequate carbohydrate intake can negatively impact training performance in many instances.