Oxidative Priority, Meal Frequency, and the Energy Economy of Food and Activity: Implications for Longevity, Obesity, and Cardiometabolic Disease
Interesting summary of research on fasting and oxidative priority of energy sources.
Some notes:
- A person's respiratory quotient (RQ) is defined as (volume CO2)/(volume O2), and can be used to measure his energy fuel mixture. Eg. an RQ of 0.85 indicates a 50/50 mix if carbohydrates and fat. Protein is estimated separately via urine/feces sample.
- Meals entail a 4-6 hour postpandrial change in metabolism to process the food
- The nature of the postpandrial change varies based on the type of food. Example: Protein causes higher rise in dietary induced thermogenesis, since there is no way to store proteins. It also causes a reduction in the use of stored carbs and fats
Oxidative order is based on how readily a fuel source can be stored:
- Alcohol has no storage capacity in the body, consumed first
- Protein has very limited storage capacity in tissue, consumed second
- Carbohydrates can be readily stored as glycogen, consumed third
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Fat has almost unlimited storage in adipose tissue, consumed last
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Above can be used to understand obesity in western diet. Excess carbohydrates pre-empt burning fat, while excess fat is steadily accumulated
- Fasting first burns through glycogen stores, then burns fat from adipose tissue
- "Chronic postpandrial state" due to ready availability of food at all times
- Cold changes metabolism to favor burning fat. The authors have a separate article entirely dedicated to this topic.
link