I would like to point out that this question might be to general for a complete answer but I will do my best in point out some points.
When it comes to health, eating healthy is important regardless if your in a low stress or a high stress environment, and while I do realize you asked about eating healthy in a low stress environment I felt it was important to point out some of the stress inducing problem.
Effect of stress
Stress causes the release of hormones in your blood stream and it arrives and affects your entire body (From lectures).
The extended exposure to stress has effects on cognitive and mental health, (Sonia J. et al.) and immune system (David N. et al.) among others.
Effects of Food
This one is probably self explanatory, between not eating the amount of vitamins required to problems such as obesity there's plenty we could talk about.
-For vitamins I like to refer to this very informative and complete website:
-Due to byproduct of protein metabolism ammonia, excess of protein intake can have toxic effects(William V. et al.).
Even if you live in a low stress environment the health issues obtained from unhealthy eating remain.
I hope This was useful to you and, even if not completely, answered your question.
Sonia J. Lupien, Bruce S. McEwen, Megan R. Gunnar & Christine Heim ; Effects of stress throughout the lifespan on the brain, behaviour and cognition
David N Khansari, Anthony J Murgo, Robert E Faith. Effects of stress on the immune system
William V. McDermott, Jr., M.D. ,Metabolism and Toxicity of Ammonia