What Are Macros? Protein, Carbs and Fat Explained

Last updated: November 2026

Macros, short for macronutrients, are the three nutrients your body needs in large amounts: protein, carbohydrates and fat. Each one supplies calories. Protein and carbs have 4 calories per gram, and fat has 9. Together they make up your total calorie intake, which drives weight change. The three macros Carbon sets and adjusts are protein, carbs and fat.

Protein is essential because it provides us with the building blocks for the construction of all body proteins. For those exercising and breaking down muscle regularly, it's vital to have enough protein in your diet to help rebuild muscle tissue. For those dieting, it helps keep you more full and shifts the weight loss more towards body fat instead of muscle. It also helps you burn more calories when compared to carbs and fat because it takes more energy to digest, process, and utilize. Protein has 4 calories per gram.

Carbs are important because they provide glucose, one of the primary energy sources in the body. Red blood cells, your central nervous system, and the brain all run exclusively on glucose (though the brain can switch to ketones in periods of glucose deprivation). Carbs can be stored as glycogen in the liver and muscles to be used as an energy reserve during intense activity or fasting/calorie deficit periods. Carbs have 4 calories per gram.

Fat is essential because it makes up the membranes of all cells in your body. It's also a rich source of energy with unlimited storage capacity. Excess calories from fat can be stored as body fat and used as a fuel reserve during times of starvation/caloric deficit to provide energy for working tissues. Fat has over double the energy content of protein or carbs and provides 9 calories per gram.

Another macro worth mentioning is alcohol or ethanol. Though not typically thought of as a macro, it does contain 7 calories per gram and can contribute a significant amount of calories to someone's diet. If you are going to consume alcohol, you need to understand how to track it accurately in Carbon. Here's an article to help explain how to do this.

It depends on your body, your goal and how active you are. Protein is the best place to start. Carbon uses 2.2 g of protein per kg of lean body mass as a general starting point, then fills in carbs and fat around your calorie target and diet preference. See the high protein foods list for easy ways to hit it.

Your targets shouldn't stay frozen, either. In Carbon, you complete a weekly check-in, and the app reviews your weight trend and what you logged, then updates your macros based on your progress.

Are macros and calories the same thing? No. Calories measure energy. Macros are where those calories come from. Two days with the same calories can have very different amounts of protein.

Do I need to track macros or just calories? Calories drive weight change. Protein affects how full you feel and how much muscle you keep while dieting. Tracking macros, protein first, covers both.

What's the best macro ratio? There isn't one best ratio. Hit your protein target, then split the rest of your calories between carbs and fat in a way you can stick with. Carbon lets you pick a diet preference: balanced, low carb, low fat, keto or high protein. Learn more about Diet Preferences.

Want your macros set for you? Carbon sets your targets from your stats and goal, then updates them at each weekly check-in based on your progress. Start a 7-day free trial.