You want to know the secret to staying healthy? Eat right, and exercise.
What, you need more? OK, eat fruits, avoid excess starches and fats, and do aerobic exercise 3 times a week for 30 minutes or more.
If we keep going further, we could get into a variety of prescriptive systems for achieving a balanced diet and exercise routine. Assuming you find a winner among the proposed systems and you have detailed advice on how to achieve an ideal eating and active routine, at best what you have is a blanket set of guidelines.
And truthfully, the guidelines will most times not be far from what’s common knowledge on the subjects of eating and exercise. People don’t hire personal trainers and pay for dietary meal plans because they haven’t figured that fast food and sedentary habits lead to double chins. They pay for these things because they need help with practicing within guidelines. They know and have likely tried to practice within commonly accepted guidelines, but for a number of reasons it’s usually difficult, and the status quo wins. Guidelines are often hard.