13.3: Energy Expended Upon Eating
- Page ID
- 65389
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The energy expended as a result of eating is not completely understood. We do know it takes energy to digest food and absorb and assimilate nutrients into the body, e.g., replenish liver glycogen, convert “extra calories” to body fat. This energy use is highest during the first 2 hours after eating and then subsides (this is why basal metabolism is measured several hours after eating).
An analogy is the processing of supplies delivered to a manufacturing plant. When supplies arrive, the plant expends energy to open boxes, distribute supplies, discard or recycle packaging, etc.
Composition of the diet has some effect on energy expenditure (protein the most, carbohydrate less, fat the least). But the composition of our diet is a mixed one (i.e, not pure protein, carbohydrate, or fat), and the energy used is about 5-10% of calories consumed, regardless of the composition of the diet. This means that if we take in 2000 calories, we pay a tax—or get a discount—of about 100-200 calories.
We can feel warm after eating because of this increased energy expenditure. In fact, we can use this to our advantage when we’re out camping in cold weather. By eating before climbing into the sleeping bag, we feel warmer and find it easier to sleep.