You gain weight by eating too much food, and you lose weight by eating less food than your body requires to maintain its current body weight.
“Macronutrients,” or “macros,” refers to three types of nutrients that your body needs large amounts of to stay alive:
You can look at your food intake in terms of calories, but you can also look at in terms of macros, because one gram of protein and carbohydrate both contain about 4 calories, and one gram of fat contains about 9.
So, for example, you could simply aim to eat 2,000 calories per day any which way, or you could be more precise and aim for 200 grams of protein (~800 calories), 200 grams of carbohydrate (~800 calories), and 45 grams of fat (
If you’re very overweight (over 25% body fat for a man and over 30% body fat for a woman), then drop this to 1 gram of protein per pound of lean body mass per day.