Some Macro/Micro as a Percentage of Calories
Like saturated fats... <10% normally, <6% if you have had a heart attack 
Anti-flame clause: Of course, there are studies that show food source matters too, so those fats from whole foods are not as wicked as processed foods. But still, it is a metric. It would apply to a host of other targets people have like Keto as well.
So like a target could be 6% and max tolerable 10% and as you went through your day, you could adjust what you ate to target your need.
*maybe as simple as being able to flip the units from g to % as make it clearly part of the dynamic batch of values
Thanks