The number of meals being provided by council meals on wheels services has dropped by a third in five years, a BBC investigation has found.
The Older People's Commissioner for Wales has expressed concerns that people will not get a hot meal every day or see another person.
In some areas private companies have filled the gap but provision is patchy, with no service in some council areas.
The Welsh Local Government Association said councils faced £300m budget cuts.
The freedom of information request by Radio Cymru showed a fall of 32% from 2009 to 2014 across the 19 councils which responded.
Some local authorities now only provide a fortnightly service and deliver frozen meals.
Iwan Williams, from the Older People's Commsioners' office, said: "The meals on wheels service is vital to the health and wellbeing of older people across Wales, not only for physical reasons but also mentally.
"In terms of the meals, it's important old people have a warm nutritious meal at least once a day.
"It is imperative not only for their physical health, but also the relationship they develop over time with meals on wheels providers.
"It is also important in terms of mental health and how to combat loneliness."
The WLGA said councils in Wales were facing huge financial challenges.
A spokesman said: "With public sector austerity expected to last well into the future it is unavoidable that all councils in Wales will need to consider new ways of delivering services, new ways of charging for services and, where unavoidable, ways they can scale back existing levels of provision."