No. In a large international study, energy expenditure stays stable between ages 20 and 60 when adjusted for fat-free body mass. It only declines after 60, by about 0.7% per year.[1] If you gain weight more easily after 40, these data say it is not because your metabolism fell off a cliff.
What does the research say about metabolism after 40?
Total energy expenditure is the energy your body burns per day: basal metabolism, digestion and movement combined. A research team of 59 authors measured it with the doubly labeled water method, which is considered highly accurate.
The data come from people aged 8 days to 95 years from around the world. Adjusted for fat-free body mass, expenditure stays stable from age 20 to 60. After that it declines by about 0.7% per year.[1] The popular idea that metabolism tips over at 40 finds no support in these data.
Why do you gain weight more easily after 40 anyway?
A single cause cannot be derived from the study. Obvious candidates are less muscle mass and a daily life with less movement. You can influence both.
Even resting metabolic rate depends less on age alone than assumed. A longitudinal study with 997 participants and up to 13 years of follow-up found that resting metabolic rate declines mainly because of chronic disease such as COPD, diabetes, heart failure or kidney failure.[2]
What does this mean for your training?
Metabolism boosters, cures and special diets target a problem the data do not show. Levers with substance are strength training, more daily movement and an energy balance that fits your goal.
On strength training: a meta-analysis of 24 trials with 951 older adults diagnosed with sarcopenia found clear improvements in grip strength, walking speed and leg strength. Muscle mass itself did not change significantly. Three sessions per week turned out to be the most effective frequency.[3] So expect strength training to deliver more strength and function first, not automatically more visible muscle.
In short
- Between ages 20 and 60, energy expenditure adjusted for fat-free mass stays stable.
- A decline of about 0.7% per year starts in the data only after 60.
- Longitudinal data show resting metabolic rate declines mainly because of chronic disease.
- In older adults with sarcopenia, strength training improved strength and everyday function, with three sessions per week the most effective.
Frequently asked questions
At what age does energy expenditure decline?
In the study from about age 60, by roughly 0.7% per year. The figure refers to expenditure adjusted for fat-free body mass.[1]
How reliable is the study?
Do I have to eat less after 40?
These data do not imply a blanket cut. How much you should eat depends on height, activity, muscle mass and goal. If you have weight goals or pre-existing conditions, talk to your doctor or a nutrition professional.
Sources
- Pontzer, H., Yamada, Y., Sagayama, H., et al. (2021). Daily energy expenditure through the human life course. Science. doi:10.1126/science.abe5017Study type: Cross-sectional study, doubly labeled water method, ages 8 days to 95 years, international cohort
- Zampino, M., AlGhatrif, M., Kuo, P.-L., Simonsick, E. M., & Ferrucci, L. (2020). Longitudinal Changes in Resting Metabolic Rates with Aging Are Accelerated by Diseases. Nutrients, 12(10), 3061. doi:10.3390/nu12103061Study type: Longitudinal study (Baltimore Longitudinal Study of Aging), n = 997, up to 13 years of follow-up
- Yan, R., Chen, Y., Zhang, R., He, J., Lin, W., Sun, J., & Li, D. (2025). Optimal resistance training prescriptions to improve muscle strength, physical function, and muscle mass in older adults diagnosed with sarcopenia: a systematic review and meta-analysis. Aging Clinical and Experimental Research. doi:10.1007/s40520-025-03235-wStudy type: Systematic review and meta-analysis, 24 RCTs, n = 951
Limits of these statements: The studies cited provide averages. Individuals can deviate, for example because of illness or medication. Cross-sectional data show differences between age groups, not the development of individual people.
Note: This article is for general information and does not replace medical advice, diagnosis or treatment. Talk to your doctor before you start training, especially if you have pre-existing conditions.