One question I often found myself asking when I decided to go on a 14 water fast was what the body burned first — fat or muscle? The answer to that question is more straightforward that I thought.
Our bodies get their energy by breaking down carbohydrates, muscle and fat, so understanding the order of nutrient breakdown can help you save or build muscle mass and increase the rate of fat burn.
Your body’s first go-to source of energy is carbohydrates because they are are easily accessible and turned into energy. After the carbohydrates from food eaten are used up by the body, your cells begins to tap into the glucose (glycogen) stored in your muscles and liver for energy.
Glycogen stores, which vary in each person, str typically depleted within 24 hours, forcing your the to begin breaking down other compounds for energy.
When glucose and glycogen are not available, triacylglycerols — fatty compounds present adipose or fat tissue — are the next up for metabolishm. With nine calories per gram, fat is a high-energy source that provides an efficient fuel source.
Additionally, the human body metabolically prefers to preserve lean body mass, so it breaks down fat stores for fuel as much as possible. Only when fat stores are extremely low or depleted does it begin to break down protein.
After glucose and fat stores are depleted, the body proceeds to breaking down muscle into individual amino acids for energy as a last resort. It cannot store amino acids like it does carbohydrates and fat, so it must break down muscle to make them.
As you probably guessed, we need muscle tissue to survive and move, so the body tries to preserve as much of it as possible at all times, metabolizing it only after all other energy sources — carbohydrates and fat first — are exhausted.
Understanding how the body generates energy will certainly help you to more effectively achieve your diet and training goals, but there are few things that must also be considered. For starters, if you’re looking to put on muscle or increase overall strength, a diet lacking in calories and complete proteins will prevent muscle gains. The muscle damage that occurs during exercise cannot be fixed and muscle size or strength may decrease.
Consult with a dietitian and trainer or do your own research to build a healthy, balanced diet that will help you reach your goals.