The World Health Organisation defines “health” to mean:
“Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.”
Apart from this there seems to be no universally agreed definition of the phrase “healthy eating“. In the UK the NHS talks about a “healthy, balanced diet” in this way:
“Eating a healthy, balanced diet is an important part of maintaining good health, and can help you feel your best. This means eating a wide variety of foods in the right proportions, and consuming the right amount of food and drink to achieve and maintain a healthy body weight.”
https://www.nhs.uk/live-well/eat-well/
Perhaps the best explanation we have seen comes from Canada’s British Columbia HealthLink:
The Meaning of Healthy Eating in British Columbia
The Meaning of Healthy Eating in British Columbia is intended to provide a consistent understanding of healthy eating for the purpose of developing policy and strategies for healthy eating in British Columbia.
What is Healthy Eating?
Healthy eating is a pattern of eating that contributes to best possible health through positive relationships with food and diverse, balanced food choices that meet a person’s needs for nutrients and energy.
Why is Healthy Eating Important?
Healthy eating promotes and supports social, physical, and mental wellbeing for all people at all ages and stages of life and contributes to the overall health of individuals, families, and communities. Healthy eating helps minimize the risk and occurrence and supports the management of disease.
https://www.healthlinkbc.ca/healthy-eating/professionals/healthy-eating-meaning