How can I help my parents adopt a healthier diet?

My parents are into their 60s now, and have long cemented their food preferences and eating habits. They prefer to eat lots of empty carbs because that’s what they grew up eating, and it’s comfort food to them. My mother is also particularly fond of the skin on chicken. At the same time, she is trying to lose weight. I suggested that they both switch out white rice for brown rice, white bread for wheat bread, more healthy fats, less sweets, etc. They tried it out for a little while but had trouble following through and being consistent. They said their bodies just don’t feel right when they aren’t eating the foods they’re used to.

It pains me to see them jeopardize their health when there’s something they can do about. I know it’s hard for them to change because it’s not simple—they have the will but it’s a behavioral condition that they must change.

Does anyone have advice on how they can make permanent changes to their diet?