We've always been at war with Easttransfats, right?
I mean some things are simple. Smoking is pretty unambiguously bad for you. But nutrition is not simple, and is probably individual due to genetic factors.
Stress is a killer. Smoking can reduce stress. Nothing is simple.
It's more complex than even that. There is growing evidence that the active genes in our adult bodies are impacted by the food we had as kids, even before birth. So there may be no 'ideal diet' that an adult can start. Some damage done long ago may not be reversible, and switching to a radically different diet may come with patient-specific downsides that we little understand. The most known difference is in the efficiencies by which adults absorb nutrients. Grow up with plenty of food and you don't harvest every little calorie from your food. Grow up hungry and your body might scrounge even when as an adult you have plenty of available food. The same may likely be true for various micro-nutrients.