Things the body does: use energy

Your body has the amazing ability to take in, store, regulate, and burn energy to keep all of its systems functioning. It does this in the "fed state" when calories are entering the system, in the "fasting state" when no calories are coming in, and even in the "exercise state" when energy needs are dramatically increased.

Energy sources:

Protein - 4 calories per gram
Carbohydrate - 4 calories per gram
Fat - 9 calories per gram
Alcohol - 7 calories per gram

Metabolic flexibility:
A "flexible" metabolism describes the ability of the body to use either carbohydrate or fat as the main fuel source, and to switch from one to the other efficiently when needed.

Why it matters:
When the metabolism loses flexibility, the body primarily loses the ability to burn fat as a fuel source and it relies excessively on glucose (carbohydrate). Excess fat accumulation in tissues impairs normal functioning and leads to insulin resistance, diabetes, cardiovascular disease, and fatty liver, among other conditions.

Metabolic flexibility is lost when people:

Become sedentary
Become heavier
Become older

What you can do:
Your body is designed to have the flexibility to use one of several fuel sources - mainly fat and carbohydrate - depending on available food. To maintain this proper function:

Keep moving. 150 minutes of exercise per week or 10,000 steps per day are two common targets suggested by experts.
Stay lean. Choose healthy foods and healthy portion sizes in order to maintain a healthy body weight.
Sleep enough. 7-9 hours of sleep nightly helps to maintain metabolic flexibility.

Going Deeper:
Journal article: Metabolic flexibility in health and disease

Have a wonderful week,

Dr. Topher Fox

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