Ageing reduces energy expenditure through multiple pathways at once, with muscle loss playing the largest role. The research consistently points in the same direction, but is largely based on observational studies and small interventions. In practical terms: losing weight at an older age is achievable, but requires strength training as the core of the approach and professional guidance to prevent unwanted muscle loss.
As we age, resting metabolism declines, spontaneous movement outside of exercise decreases, and less heat is produced after meals. All these changes together mean that, at the same calorie intake, you burn less energy than you once did. This effect cannot be attributed to a single cause, but rather to several small shifts occurring at the same time.
One of the biggest drivers behind this lower energy expenditure is muscle loss. From middle age onward, muscle mass gradually declines, measured in older women as an average loss of 2.4% in muscle strength per year over ten years. Muscle tissue burns more energy than fat tissue, so having less muscle also means lower energy expenditure at rest. At the same time, fat mass increases and the body becomes less sensitive to insulin, which makes weight management even harder.
Moving less accelerates this process. Low physical activity is associated with a faster decline in muscle strength in older women, and this relationship held up in both cross-sectional analyses and long-term measurements. The good news: this is modifiable. Moving more slows the loss.
Losing weight at an older age is achievable through a combination of diet and exercise, but it requires extra care. When losing weight at an older age, you lose not only fat but also muscle mass and bone density, which can be harmful in the long run. Most of the interventions studied reported this additional loss. Guidance is therefore not a luxury but a practical safeguard. Very little research has been done on the long term (longer than one year): only one small pilot study looked at sustained weight maintenance in older adults.
Strength training is the best-supported strategy for slowing muscle loss and maintaining energy expenditure. In older adults, it increases muscle mass and muscle strength and improves body composition. Three training days per week is recommended for optimal strength development. Notably, qualitative research found that older participants in exercise and nutrition programmes had weight loss as a personal goal, while the programme was aimed at improving muscle. That expectation makes sense: building muscle and losing weight do not always go hand in hand on the scale, but having better muscles does make losing weight easier over time.
Based on observational studies, one model-based analysis of energy expenditure, and one small pilot study on long-term lifestyle intervention. Strength training in older adults is the best-supported component (multiple studies, causal relationship). The long-term effects of weight loss in older adults are underrepresented in the literature.