What are the benefits of creatine for people who exercise very little?
For inactive middle-aged and older adults, creatine (5 grams twice a day for 12 weeks) can improve muscle mass and muscle strength, even without exercising. Early signals for memory effects exist, but they are too preliminary to rely on.
Two grams per day is not the dose that has been studied: in a 12-week study involving non-exercising adults aged 45 to 65, participants took 5 grams of creatine twice a day. Without any training at all, their muscle mass increased in a meaningful way, and their muscle strength and muscular endurance also improved.
That same study showed favourable changes on several memory and cognitive tests. The researchers themselves stress that these are exploratory findings, not an established benefit. The same applies to improvements in blood fat levels and a measure of longer-term blood sugar control: there are signals, but they are not yet well enough supported to allow firm conclusions.
For people with chronic joint or muscle pain, such as osteoarthritis, some nuance is needed. Creatine without training appears to have little effect in that group. When combined with strength training, studies in people with osteoarthritis did show greater improvements in muscle strength, muscle mass and quality of life than training alone, although these are small studies.
On safety: neither study reported any serious side effects. Creatine was well tolerated, both in healthy, inactive adults and in people with chronic pain complaints.
This answer draws on two studies. The findings in inactive adults come from a single study in non-exercising people aged 45 to 65; that study was carefully designed but stands alone. The findings in people with chronic pain come from a summary of eight small studies involving 189 participants in total. Both sources are therefore limited in scale, and the cognitive and metabolic outcomes within them are explicitly flagged as exploratory.