On page 84 of "Fat, fighting the obesity epidemic" (2001, Oxford University Press, New York), Robert Pool relates, 
  "Almost any doctor who works with the obese will tell you that successful long term losers (of weight) are a monomaniacal lot, completely obsessed with their weight. Bruce Schneider a clinical researcher now at the Food and Drug Administration, was working in Hirsh's lab (at Rockefeller) in the early 1980s when Leibel advertised for people who had maintained a weight loss of 100 pounds for at least a year and a half. 'He got six people,' Schnieider recalls, 'and all of them were wacked.' One woman had to - HAD TO - jog six miles a day. If she didn't, she became extremely upset. Another constantly fantasized about food. 'You were basically dealing with constant starvation,' Schneider says."
 
This month's issue of the journal Obesity has an examination of this issue using the German Weight Control Registry (GWCR). (1) We have a similar thing called the National Weight Control Registry (NWCR) of the few and the proud who have managed to maintain a significant amount of weight loss. But the Germans have looked at an issue that has not been addressed by our registry. They asked these weight loss maintainers questions about eating related and general psychopathology and found a lot. For example 8% of the GWCR participants reported 4 or more binge eating episodes within the last 28 days. This is the same 8% that has been reported by our NWCR but we say that that is the same as the general American population. German population controls don't do that. Fifty percent of GWCRers were clinically obsessed with the importance of weight and shape in their self-evaluation. They were also 4 times more likely to practice "compensatory behaviors" defined as things like "driven exercising" (compulsive exercising as a means of controlling weight, altering shape or amount of fat, or burning off calories), or fasting for more than 24 hours. They also were significantly more likely to weigh themselves more than once a day.
Americans might think that these things are "healthy obsessions" and this kind of commitment is probably indispensable for weight loss maintainers to stay in control. But these Germans authors see this as more problematical.
These thoughts resulted in the following e-mail from me to these authors:
Dear Sirs,
is it possible from your data to correlate degree of psychopathology items with degree of weight loss? Part of the definition of anorexia nervosa is >15% loss from "normal" but it is widely accepted that that loss from any weight is equally "hard." The average BMI change of GWCR you reported was 22.6% (33.2->25.69).
vielen Dank,
John DiTraglia MD
I'll let you know what they say.

1. Feller S et al. What distinguishes weight loss maintainers of the German Weight Control Registry from the general population? Obesity. 2015;23:1112-8.