Question

Which of these contains the most authoritative data on diet and weight loss?

Answer 1

Most authoritative data would probably be found by a doctor or a nutritionist.

Answer 2

Most authoritative data would probably be found by a doctor or a nutritionist. These are people who create specific diets that suit your body and they monitor weight loss of each individual. The least would definitely be things like the internet or from friends or from a magazine since these are often incorrect and way too general.