Fully agree that psychological factors are the main factors that explain sustainable success in weight/health management. On the articles: seems fine to distinghuish 4 types of motivation, but they are of course not exclusive: they might play a role to some extent at the same time. The interesting question is how they interact: can they reinforce each other, or do they impair each other? Do external motivations decrease internal ones (which would be a problem), or are there ways to frame them that make them contribute to internal ones. I recollect a discussion long ago on 'things to do/buy' when reaching (intermediate) goals. Perhaps it would help to see them not as motivations for keeping on track (external), but as celebrations for something that is already positive in itselve.
5-2-diet-chat-f6/rewarding-yourself-for-reaching-mini-goals-t8666.html?
In relation to fasting the main issue seems to be how can we make sure that the activities of fasting and naturally also not having to bother on other days (or times of the day) are experienced as something that is easy/fun/pleasure as such. For me not having to count calories and not having to be selective in food choice (yes, I do like my carbs

) are an essential part of that. It enables me to rely on internal motivations for most of the time, and to celebrate some rewards that are close to being external also on a few occasions