The description for the book Think Thin, Be Thin: 101 Psychological Ways to Lose Weight on Amazon has this to say about its advice:
Old standards like keeping a food diary and finding simple ways to burn calories (like gardening or taking the stairs at work) are mixed with creative ideas like becoming your own advice columnist for a day and watching specific comedy movies that also offer encouragement for change (think Groundhog's Day).
Aside from getting the title of the film wrong, it's a nice positive reference to Groundhog Day. But, Groundhog Day is not just a nice encouraging film for folks trying to lose weight. It's also occasionally a metaphor for the way people struggle with weight loss. For example, Certified Personal Trainer John Kent mentions the film in an interview with PanacheVue'. He says:
The combination of the habit-based nutrition coaching and our science based exercise program, is our recipe for your long-term success.
This way your weight loss effort is not like the movie Groundhog Day where you’re always starting over with the next new diet, new exercise program, new pills, new gadget, etc.
FU Diet takes it even further in an article (that gets the title wrong, but not as wrong as the article itself) called "Groundhog’s Day Is the Key To Weight Loss":
Ground Hog’s Day is the key to weight loss? Huh? Even the “Cookie Diet” doesn’t sound as ridiculous as this. Keep reading… Remember the 90’s Bill Murray movie Ground Hog’s Day? This is the one where he plays Phil, the arrogant, crotchety weatherman who wakes up to find out that he is reliving the same day, over and over again. Everyday turns out to be the same day, all starting with his alarm clock going off to the Sonny and Cher song, “I Got You Babe.” At first Phil attempts to have some fun since there are no long-term consequences to his actions, but eventually he realizes he is doomed to live the rest of his life in the same place, living through the same circumstances, and doing the same thing, day after day after day after day, with seemingly no escape. He’s living in his own personal exile.
Personal exile is also the doom of the weight cycler. They relive the same experience over and over again, ending up in the very same place each time...
Let's ignore, as painful as it is, the ridiculous take on the title of the film (which isn't a typo, of course, because they use it twice). The article goes on for a bit about weight cycling before coming back to the film:
Why is this happening? Let’s look to the Groundhog Day movie for insights. The only way that Phil is able to overcome his doom is to find a new, more fulfilling way of living. If he does not do this, he will be forced to relive the day again. Each day he relives, he makes some mistakes, but not until he confronts his core struggle (in his case, fear of intimacy and fear of loss), how it leads to the various problems in his life (e.g., people disliking/avoiding him), and finds a new way of living, will he be released from his personal exile. A weight cycler has the same task. It is about identifying the core struggle and how it is keeping you caught in the cycle. The work involves these steps.
It's an interestingly specific take on Phil Connors, to suggest he fears intimacy and loss. I'm not sure either of those things hold up within the film, even if they don't actually contradict what we do know of the character. But, nothing in the film specifically points to Phil's fear of intimacy as the source for his occasionally antisocial behavior--you know, insulting everyone, ridiculing his own job, abandoning Stephanie back in Pittsburgh when she's so obviously unstable (and into witchcraft, or at least knows where the witchcraft section of the bookstore is)... but nevermind Stephanie since she's not in the film but Ramis' second revision of the script.
Actually, don't nevermind Stephanie... or alwaysmind Stephanie... nowmind Stephanie anyway, because something occurred to me. The Stephanie bits are a bit silly anyway, which is plenty of reason to have cut them, but they also would have made the ending of the film a bit awkward. Phil makes himself into a better person, wins Rita's love, then he's going to head back to Pittsburgh where Stephanie not only has no reason to think her curse worked but also still has a thing for Phil and, being crazy and all, just might kill him or Rita or both. The film as it is has an awkward enough ending if you take the time to think about it; seriously, Rita who we've seen won't go to bed with the guy who just gave her a "perfect day" but will go to bed with a guy who plays the piano and sculpts her face in snow and is well liked by strangers... well, maybe Rita's just got even more exacting standards than those she lays out for Phil at the start of "date night."
But, I was talking about weight loss. Sherry Pagoto at FU Diet might be right about Phil's fears, but really, there's no definitive evidence for either of the fears she mentions. But, moving on, she gets to the identification of one's core struggle. She explains as a comparison Phil Connors' core struggle:
For Phil, the way he treated people by being inconsiderate and arrogant was his way of avoiding relationships, and as a result, he would not have to confront his fears and anxieties about intimacy and loss. This resulted in loneliness, rejection, and dysfunctional relationships, hence, the unsatisfying part of his life.
It is quite common that weight cyclers have a core struggle that locks them into their cycle as well...
Again, her argument here about Phil and his problems--it doesn't contradict anything in the film. But, it also doesn't resonate with me. And, at this point, I trust my judgment about this film and its content. Phil might fear intimacy, but the film does not tell us this. Phil might fear loss, but... actually, I'm not sure this rings true even as subtext. Phil's problem with O'Reilly dying is not about fear of loss (and really, what other loss does Phil suffer in the film?) but about Phil realizing his powers are finite, he cannot do whatever he wants on Groundhog Day. There's a limit beside geography. Not being able to win over Rita in the second act is a lesser version of this same thing. But, neither one is about loss but more about power.
Pagoto gets back to Groundhog Day at the end of the article, asks, "How will I know if it’s working?" The answer once again invokes Groundhog Day:
Well, Sonny and Cher will stop singing. No really, you will stop cycling. If you continue to cycle, something is still wrong and you may need to dig deeper. Make every effort to figure out what went wrong or you will be vulnerable to it happening again...
That's a great description of Phil Connors' journey, cycling and cycling until it seems like he may have found a purpose--hedonism, Rita, saving O'Reilly--but after each one he has to dig deeper until finally he's making everyone's lives better (as much as he can).
Pagoto ends with one more reference to Groundhog Day:
Spoiler: In the end… Phil got the girl.
Today's reason to repeat a day forever: to get the girl? to make lives better? to have fun? all three?