15th February 2021 – by Paz García

Over-60s with a good appetite have more diverse and different communities of microbes in their gut than those with a poor appetite, according to a new study from King’s College London and the University of Southampton.

The study, published in the Journal of Cachexia, Sarcopenia and Muscle, is the first to identify differences in gut bacteria based on appetite between otherwise healthy older adults.

In addition, the researchers found that lower appetite was associated with reduced muscle strength and function, with gut bacteria as a potential link between the two.

Co-first author Dr Ruth Bowyer, Research Associate at TwinsUK, King’s College London, said:

“Loss of appetite is very common in older people, and this can have serious consequences including loss of muscle mass and function. Our research is the first to explore the links between appetite and gut bacteria, and how this may be related to muscle strength.”

The team used appetite questionnaire answers to identify 102 twins who had small appetites and 102 twins who had greater appetites, and compared their gut bacteria. The two groups of twins were otherwise as similar as possible in terms of age, body mass index, calorie consumption, antibiotic use and other factors that could impact gut bacteria.

The researchers found that twins with a poor appetite had less variety in their gut bacteria than twins with a good appetite. They also found that twins with healthy appetites were more likely to have microbes associated with diets high in vegetables and fibre.

The team then looked at participants’ muscle strength, based on previous muscle strength assessments completed during clinic visits, and found that twins with a lower appetite had reduced muscle strength compared to twins with a good appetite.

Co-first author Dr Natalie Cox, Clinical Research Fellow at the University of Southampton, explained:

“A lower appetite can lead to undernutrition, which in turn can lead to loss of muscle mass and so reduced muscle strength. We know from previous research however that a poor appetite is also linked to loss of muscle strength independent of overall weight loss.

“We now need studies to understand how exactly appetite, gut bacteria and muscle function affect each other and in what order. This could inform the development of treatments in the future to preserve muscle mass and function, to improve health in older age.”