Well I just finished watching this and I have mixed opinions. I for one can certainly not fly all over the world to sample different cultures take on food as much as I'd like to. You have to bear in mind the climate and lifestyle as well as food.
Secondly with regards to their weight/bmi, using your weight for height and bmi alone wont be accurate everytime, but looking at that little receipt they had looked like it showed, weight, height, muscle mass, fat mass, water mass etc., she also measured their waists; which is a good indicator as if your muscle mass in high and therefore weigh more, you waist should still be in a healthy region for your height.
I look forward to the next part so I can formulate some opinions!!