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This Hidden Metabolic Sign May Point To Malnutrition In Older Adults
When an older parent or grandparent starts losing weight without trying, eating less, or struggling with everyday tasks, it's easy to chalk it up to aging. But these changes can also signal malnutrition or muscle loss. A recent study1 explored whether resting metabolism, or how much energy the body burns at rest, could offer another clue to these health concerns.
About the study
Researchers studied 141 hospitalized adults in Beijing, with an average age of 74.8, to see whether resting metabolic rate (RMR) was linked to malnutrition and sarcopenia, the loss of muscle mass and strength that can occur with age.
RMR is the energy your body uses to keep essential functions running while you're at rest. Researchers measured it using a test called indirect calorimetry, which estimates energy use by analyzing the gases a person breathes out.
They also assessed participants' nutrition, muscle mass, and physical function to see how these factors related to their resting metabolism.
A lower resting metabolic rate was linked to malnutrition and muscle loss
Of the 141 participants, 74 (52.5%) had malnutrition, while 67 (47.5%) did not. Those with malnutrition had lower resting metabolic rates than those without it.
Researchers also compared RMR relative to body weight.
After accounting for age, sex, chronic conditions, and physical function, they found that people with a higher RMR relative to their weight had lower odds of both malnutrition and sarcopenia.
Researchers also identified a preliminary RMR level that helped distinguish participants who had malnutrition from those who didn't.
People whose measurements fell below this level were more likely to have malnutrition, low muscle mass, and poorer physical performance. However, this cutoff needs to be tested in larger groups before researchers can know how reliably it identifies people at risk.
Why metabolism & muscle health are connected
Your body burns energy around the clock, even while you're sitting or sleeping.
This energy powers essential functions such as breathing and organ activity. Muscle tissue also contributes to resting energy use, so changes in muscle mass can affect how much energy the body burns.
Nutrition and muscle health are closely linked. Not getting enough calories or protein can contribute to muscle loss, which may make everyday activities harder. Illness and other health problems can also affect appetite and nutritional needs.
However, this study measured participants at a single point in time, so it can't establish whether a lower resting metabolic rate contributes to malnutrition and muscle loss or develops alongside them.
The relatively small sample of hospitalized adults in one country also limits how widely the findings can be applied.
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How to support nutrition & muscle health as you age
While resting metabolic rate isn't ready to serve as a standalone screening tool, a few habits can help protect muscle and nutritional health.
- Eat enough protein and calories: Adequate food intake meets the body's energy needs, while protein provides the building blocks for muscle. A health care provider or registered dietitian can help if appetite changes make eating enough difficult.
- Make strength training a habit: Resistance exercise helps preserve muscle, strength, and mobility. Bodyweight exercises, resistance bands, and weights can all help.
- Don't dismiss unexplained changes: Unintentional weight loss, declining appetite, or difficulty standing from a chair are worth discussing with a health care provider rather than automatically attributing them to aging.
The takeaway
Resting metabolism may help flag nutritional problems and muscle loss in older adults, but it can't tell the whole story. For now, unexplained weight loss, appetite changes, and declining strength are important signals to discuss with a health care provider.