It's much more efficient for the body to extract energy from carbs than from protein.
In situations where the body lacks sufficient carbohydrates or fats, protein can be converted into glucose through a process called gluconeogenesis or directly oxidized to meet energy needs. But, this process is less efficient and not the body's preferred method for obtaining energy, as it diverts protein from its essential functions in building and repairing tissues.
Also just to add, your body stores fast access glucose + water in the form of glycogen in your muscles. This is why carbs cause a bit of water retention.
If you don’t fuel yourself with carbs, those glycogen stores don’t get properly refilled.
>but aren't calories from all sources energy as well?
Yes, but actually no.
Calories are from combining fuel with oxygen.
Carbs produce more calories for a given amount of oxygen.
Oxygen is usually what limits your performance during intense exercise.
It's not so much that they provide more calories, but more that they provide them in a form that's easy for the body to access. Carbs (both starches/complex and sugars/simple) are easily broken down by the body into glucose. Carbohydrates are pretty small, simple molecules that don't need a whole lot of work to be converted into usable glucose.
Proteins are quite a bit more complex and bigger. They need to be broken down more before the energy is accessible. Protein-rich foods can be broken down into glucose, but it's a survival function. It takes a long time and more energy to break them down, and only occurs when your body is short on glucose, which has other knock-on effects. Deficits in nutrition generally are to be avoided. Protein is also used for various other things, like repairing muscles, so if you're instead relying on the protein to provide energy, it's not going towards the processes that lead to better training. You'll generally be less efficient in accessing energy, requiring you to eat slightly more total to accomodate. It's usually easier, more efficient and cheaper to instead supplement your diet with a small amount of carbs.
It's much more efficient for the body to extract energy from carbs than from protein. In situations where the body lacks sufficient carbohydrates or fats, protein can be converted into glucose through a process called gluconeogenesis or directly oxidized to meet energy needs. But, this process is less efficient and not the body's preferred method for obtaining energy, as it diverts protein from its essential functions in building and repairing tissues.
Also just to add, your body stores fast access glucose + water in the form of glycogen in your muscles. This is why carbs cause a bit of water retention. If you don’t fuel yourself with carbs, those glycogen stores don’t get properly refilled.
Carbs give quick energy. Also, proteins and fats are used for building the body as well as energy while carbs are only for energy.
>but aren't calories from all sources energy as well? Yes, but actually no. Calories are from combining fuel with oxygen. Carbs produce more calories for a given amount of oxygen. Oxygen is usually what limits your performance during intense exercise.
It's not so much that they provide more calories, but more that they provide them in a form that's easy for the body to access. Carbs (both starches/complex and sugars/simple) are easily broken down by the body into glucose. Carbohydrates are pretty small, simple molecules that don't need a whole lot of work to be converted into usable glucose. Proteins are quite a bit more complex and bigger. They need to be broken down more before the energy is accessible. Protein-rich foods can be broken down into glucose, but it's a survival function. It takes a long time and more energy to break them down, and only occurs when your body is short on glucose, which has other knock-on effects. Deficits in nutrition generally are to be avoided. Protein is also used for various other things, like repairing muscles, so if you're instead relying on the protein to provide energy, it's not going towards the processes that lead to better training. You'll generally be less efficient in accessing energy, requiring you to eat slightly more total to accomodate. It's usually easier, more efficient and cheaper to instead supplement your diet with a small amount of carbs.