Some are lucky with great genes. My wife is one too.
Don’t worry about eating saturated fats, or marbled meat ever. The fat makes you feel full and you simply don’t eat as much. Unless you like the carbs as they drive the insulin response that makes your body store the fat. Avoid sugar like the plague it is.
If I could recommend 2 books I would read Gary Taube Good Calories/Bad Calories and/or Nina Teicholz Big Fat Surprise.
I don’t worry about eating anything except homogenized Milk.
I think it’s bad for your body to have protein and fat bound to each other and must be confusing to the pancreas and liver...