That's very tough. It depends on what they've done so far. If someone has researched and tried various diets, then you need to pay attention to what seems to work. The basic details of a healthy diet are fresh, real, whole, natural foods, which is difficult. So you don't combine protein and starch.
Beans are okay, in a vegetarian meal.
You don't eat anything after 8 at night. Don't mix fruit with anything, and with the diet, you only eat melons alone . You should only eat fruit in the morning, and if there's a fruit salad, there should be no melon in it. This can get a little stickier, but you eat fruit when you're hungry, in other words,. on an empty stomach. So it's good for those two parties, however, I don't recommend eating fruit for breakfast in winter or in a cold climate because you get cold.