Over-60s with a good appetite have more diverse and different communities of microbes in their gut than those with a poor appetite, a study has found.

The study, published today in the Journal of Cachexia, Sarcopenia and Muscle from King's College London and the University of Southampton, is the first to identify differences in gut bacteria based on appetite between otherwise healthy older adults.

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

The team used appetite questionnaire answers to identify 102 older people who had poor appetite and 102 older people who had good appetite, and compared their gut bacteria. The two groups 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 individuals with a poor appetite had less variety in their gut bacteria than individuals with a good appetite. They also found that those with healthy appetites were more likely to have microbes associated with diets high in vegetables and fiber.

The team then looked at participants' muscle strength, based on previous muscle strength assessments completed during clinic visits, and found that twins with a poorer 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 poor appetite can lead to poor nutrition and weight loss, which in turn can lead to loss of muscle bulk 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."