This is a retrospective analysis of the data from CALERIE, that tries to characterize the contributions of the loss of energy-expending tissues and metabolic adaptations to the reduction in resting metabolic rate following weight loss.
- CALERIE, or Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy, was a large-scale, randomized clinical trial in humans that involved a 25% reduction in energy intake over the course of a 2-year period.
Findings:
- There were significant reductions in metabolic hormones after 12 months, with the exception of IGF-1. The largest decline occurred in leptin. T3 and insulin were also significantly reduced.
- Reductions in leptin, T3, and insulin were all weakly correlated with metabolic adaptations.
- The analysis found that the primary components lost during the intervention were skeletal muscle and adipose tissue, while the remaining organs and tissues were largely preserved.
- There was substantial variability between participants in RMR changes as well as in the contributions of tissue losses and metabolic adaptations to RMR changes.
- RMR was reduced by a magnitude of ~100 kcal (~7%) in response to weight loss of ~11% achieved through caloric restriction in healthy normal weight and overweight individuals.
- Individuals who lost the greatest amount of skeletal muscle exhibited a reduction in RMR that was only ~25% explained by skeletal muscle itself, but almost entirely explained by the reduction of all energy-expending tissues.
65% of this RMR reduction was found to be attributable to the large losses in adipose tissue.
- This loss of energy-expending tissues, predominantly skeletal muscle and adipose tissue, contributed to the reduction in RMR, although on average for only ~60%, leaving the remaining 40% of the RMR reduction attributable to metabolic adaptations.
- Contrary to common belief, there was no discernible relationship between the loss of skeletal muscle, the primary lean tissue component that is lost during weight loss, and reductions in RMR.
- Conversely, the loss of adipose tissue was related to reductions in RMR and metabolic adaptations, whereby metabolic adaptations were greatest in individuals who lost the most adipose tissue.
Tissue losses and metabolic adaptations both contribute to the reduction in resting metabolic rate following weight loss (open access)
doi.org/10.1038/s41366…
#weightloss #obesity #MetabolicSyndrome #muscle
doi.org/10.1038/s41366…
#weightloss #obesity #MetabolicSyndrome #muscle
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