I feel like way too many people jump to the reductive "oh it's just that people treat you differently when you look more attractive" with these types of studies, when the truth is so much more vastly complicated and multivariate than that.

First, a lot of people don't consider the yin to the yang, or whatever. They don't consider that a lot of the reason they might be treated better is because of how they're showing up in the world and interacting with people, on an emotional level. If you're less self-conscious and guarded, because you feel more self-actualized, you're probably being more agreeable and friendly with people you're talking to, you're probably less socially anxious psychologically (not to mention neurochemically), and your demeanor is probably better. There's also the matter of improved mobility making you feel lighter and more agile, which can certainly put you in a better mood than feeling like you're moving through quicksand just walking around. It's just simple physical charisma in a lot of aspects, and oftentimes much more just in how you're feeling being written on your face, and obvious in the way you're speaking, as much as the cosmetics of being fit.

Second, there's the aspect of neurochemistry feeding into the above factors. If you're fit because you're going outside more, you might be getting more sunlight, thus driving more vitamin D synthesis, which increases serotonin levels, thus less depressed. You might be eating more balanced meals, thus getting more neurotransmitter precursors and less inflammatory compounds, which drive a lot of various mood and cognition improvements, and various other areas of your health that will affect how you feel. Strength training drives synthesis of tyrosine into dopamine, and improves function of the whole system, affecting things like receptor sensitivity and such. Endurance cardio drives synthesis of tryptophan into serotonin, as well as the endorphin system, as well as promoting neurogenesis / neuroplasticity that can help you be more mentally-emotionally adaptive.

All of these factors improve mood and give you more felt energy, which generally make you much more charismatic in ways that mostly have nothing to do with cosmetics. Additionally, being healthy and vital is an attractive characteristic that many people want to be around. Especially if you're struggling with your own health and staying on track, I'm sorry, but it can be really hard being around someone with horribly unhealthy habits. It's nothing personal, it's just sort of a "birds of a feather" thing. People feel comfortable around people with at least somewhat similar lifestyles and moods. The handful of people we're closest to heavily influence our behaviors. If you're not unshakeable with your habits, being around people who don't take care of themselves at all can be like being someone who struggles with being easily influenced into drinking being around an alcoholic.

I'm not saying all of these factors are fair, or right, but they are what they are. People shouldn't be shamed or feel guilty, as it's certainly not some sort of moral failing, nor is being unhealthy some sort of immutable characteristic. Most people struggle with keeping on track with a healthy lifestyle, and most people have had periods in their life where they were in rather tragic states in that regard.

There's simply a lot more factors at play as to why healthy people have better social outcomes than a simple "people don't like me because I don't look good". It also, frankly, can be a really condescending and superficial reduction of why people exercise and eat healthy. It also completely lets you off the hook, and blames others, as to why you may not be getting the social outcomes you want. In some cases it is other people, but it can as much be poor social behaviors that are encouraged by being unhealthy. I think the findings in this study of differences between men and women in this regard are evidence to the fact that part of it is certainly issues with other people's perceptions of obese people.

I made a major transformation in my life about 15 years ago, and while sure, the cosmetic benefits were nice, I suppose, my main intention for why I was doing it was my physical and emotional health. I was a recluse who felt like absolute garbage before, and not because anyone was shaming me or mistreating me. Part of it was my own interpretation of myself, but a lot of it was simply physiological. I felt drastically better once I got healthy, not to be confused with how I felt about myself. It's unfortunate that women have a pretty different experience in this regard, in terms of getting much more unwanted attention. For better or worse, I never had to deal with that at all. Obese = 0 unsolicited attention from women, very fit = 0 unsolicited attention from women. Being a man can be rough in that regard, but it's better than getting too much attention from people bigger than you.

When you make those changes and put that energy out into the world, you are socially appealing to different types of people than you were before. We all want to find people whom we can relate to, who have similar goals as us, whom we can share activities with. If I'm a very active person who wants people to hike with, go the gym with, maybe play sports with, that's not going to go very well if someone I'm considering a connection with who can barely get off the couch. If I'm a homebody who really enjoys a sedentary life and having unbridled freedom with food, I'd want to be around people who have a similar perspective.

All this said, there is a lot of problems with stigma, shame, guilt, and such that have no real place in our society, given that everyone has their own path in life, and not everyone needs to look like an action figure. But people should consider the deeper and varied factors related to this, and not be so quick to absolve themselves of all responsibility as to why they aren't having the social outcomes they want