New research changes what we thought we knew about calorie consumption. The analysis is based on combining data from a large number of studies, and covers people between infancy and age 95.
The fundamental finding is that the metabolic rate doesn’t change linearly with age. Instead, there are four distinct phases:
- There’s infancy, up until age 1, when calorie burning is at its peak, accelerating until it is 50 percent above the adult rate.
- Then, from age 1 to about age 20, metabolism gradually slows by about 3 percent a year.
- From age 20 to 60, it holds steady.
- And, after age 60, it declines by about 0.7 percent a year.(1)
Thus, middle age gut (the fat ring around the abdomen often found in people in their late 30s or 40s) is due to changes in activity rather than changes in metabolism.
The “freshman five” — weight gain associated with the first year in college — may result from a combination of metabolic change and a more sedentary lifestyle when studying.
Most calorie consumption is to support organ (heart, brain, liver, etc.) health, and the researchers theorize that the drop off in metabolism after age 60 accompanies a decline in organ health.
What would be useful is an easy way to monitor our metabolic rate as a barometer of health.