For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
I'm not especially familiar with the Shepherd Diet, but from what I've heard it is basically a variation of the Atkins Diet, with slightly higher unsaturated fat and protein intake. It doesn't pull meal plans from the Bible (there are very few actual meal plans that come with the program), but Kristina pushes that 'God revealed His healthy fats to her.'
I am a bit skeptical of it for a couple of reasons. For the first, Atkins and similar low-carb diets can be dangerous if not supervised by a doctor, as they work by trying to change the natural digestive process God gave us. For the second, even a cursory examination of the way people ate in scripture shows that they didn't eat low-carb diets. Bread and other grains were staples.
Even the first mention of food in scripture shows God giving mankind primarily fruit, veggies, and carbs to eat" "Then God said, “I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. "
So, I would be wary of a diet system that treats most of those natural fruit sugars and grains as to be avoided in favor of protein/fat.