Why metabolism slows after 60
Spoiler alert: you're so efficient at staying alive
As we age, metabolism doesn’t just ‘slow down,’ it shifts. And when it comes to resting energy expenditure (REE), those shifts can have real consequences, especially in older adults. REE is the baseline energy we burn just staying alive: breathing, circulating blood, keeping our organs functioning (Rawson et al., 2023). But the way our body burns that energy changes in predictable ways across the lifespan.
According to Pontzer et al. (2021), REE stays surprisingly stable from our 20s through our 50s, once body size and composition are accounted for. After 60, it starts to decline around 0.7% per year. That drop is not just about losing muscle, it reflects a slowdown in the metabolism of key organs like the brain, liver, and heart. These high-energy tissues become less metabolically active with age, so even if an older adult’s weight stays the same, their energy needs do not.
If you’ve hit a point where “what used to work” no longer does—especially around energy, appetite, or weight—it might be time to re-examine your metabolic baseline rather than just your habits.
This decline isn’t always accounted for in standard nutrition protocols. Cioffi et al. (2021) examined how well ordinary predictive equations (like Harris-Benedict or Mifflin-St Jeor) estimate REE in older adults. Their review found that while these equations may work for group-level estimates, they often fail to capture the needs of individuals over 65. This is especially problematic when precision is needed in clinical care or wellness planning.
🧮 Want to explore your own numbers? Try calculating your estimated REE using the Mifflin-St Jeor equation:
Men: REE = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
Women: REE = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
Now ask: Do these numbers align with how I feel, perform, or recover? If not, that disconnect might signal more profound shifts in organ metabolism, nutrient absorption, or energy regulation.
Pourhassen et al. (2020) added another layer by studying malnourished older patients in a hospital setting. Their measured REE was lower than predicted on admission, and after two weeks of nutrition therapy, REE increased significantly, far more than the equations anticipated. In other words, underfed bodies adapt by dialing metabolism down, and refeeding doesn’t just restore calories, it restores metabolic function, too.
Then there is the complexity of aging with obesity. Danielewicz et al. (2023) studied older Italian adults with severe obesity and found that most standard REE equations underestimated their actual needs. They developed new equations specific to this group, but even those were not accurate enough to fully replace indirect calorimetry. Age, gender, and body composition play significant roles in REE (Rawson et al., 2023), underscoring how ‘standard’ just does not cut it when working with aging bodies in larger bodies.
As people age, their metabolic stories become more individualized. Body composition changes, organ metabolism slows, and nutritional status can skew REE in either direction. Predictive equations can offer a starting point, but they are not gospel. Measured data is gold whenever possible, especially in a clinical or recovery setting.
Whether you're a clinician or just tracking your wellness, revisit energy needs at every new chapter. What served your body well at 35 may no longer be beneficial at 65. The body adapts, and your plan should too.
References
Cioffi, I., Marra, M., Pasanisi, F., & Scalfi, L. (2021). Prediction of resting energy expenditure in healthy older adults: A systematic review. Clinical nutrition (Edinburgh, Scotland), 40(5), 3094–3103. https://doi.org/10.1016/j.clnu.2020.11.027
Danielewicz, A. L., Lazzer, S., Marra, A., Abbruzzese, L., D'Alleva, M., Martino, M., Isola, M., Avelar, N. C. P., Mendonça, V. A., Lacerda, A. C. R., & Sartorio, A. (2023). Prediction of resting energy expenditure in Italian older adults with severe obesity. Frontiers in endocrinology, 14, 1283155. https://doi.org/10.3389/fendo.2023.1283155
Pontzer, H., Yamada, Y., Sagayama, H., Ainslie, P. N., Andersen, L. F., Anderson, L. J., Arab, L., Baddou, I., Bedu-Addo, K., Blaak, E. E., Blanc, S., Bonomi, A. G., Bouten, C. V. C., Bovet, P., Buchowski, M. S., Butte, N. F., Camps, S. G., Close, G. L., Cooper, J. A., Cooper, R., … IAEA DLW Database Consortium (2021). Daily energy expenditure through the human life course. Science (New York, N.Y.), 373(6556), 808–812. https://doi.org/10.1126/science.abe5017
Pourhassan, M., Daubert, D., & Wirth, R. (2020). Measured and Predicted Resting Energy Expenditure in Malnourished Older Hospitalized Patients: A Cross-Sectional and Longitudinal Comparison. Nutrients, 12(8), 2240. https://doi.org/10.3390/nu12082240
Rawson, E. S., Branch, J. D., & Stephenson, T. J. (2023). Williams' nutrition for health, fitness & sport (13th ed.). McGraw Hill