It is going to depend a fair bit on how tall you are, how active you are (both for how strong you are to carry the weight, and for how soon you notice the difference in weight), and how you are built. Personally I've only put on ~65 pounds in adulthood (over many years) so I couldn't fully answer that. But I can say what I've observed of my wife who put on over 90 pounds in the first half dozen years that we were together, and then has bounced around near that max in the many years since.
For reference:
-She started at a BMI of ~23, and ended up ~38..
-about 5'7",
-all hip and thigh (even when thin).
-When we met she was walking about 90 minutes most days (to/from university) plus walking between classes and at a part time job, but didn't do other activities. So strong legs and decent endurance but not otherwise especially fit.
We got married about 2/3 of the way through that, and at that time she really hadn't noticed much changing her life with the weight gain, other than having to move to plus sized clothes (a LOT less options). But at our wedding she realized how much her ankles and feet swelled up when standing for a long time at that size, kind of puffing out of her shoes a bit by the end.
Around that same time she tried to pick up some winter sports, but found that combined with previous ankle damage the weight was too much for her with skating, she didn't have the strength to support her ankles (she had barely skated before so didn't have the balance and technique that would have helped there). And with cross country skiing she kept falling at first, and eventually we realized that her thighs were two thick for her to follow existing set tracks (which have the two skis really close together)
At about bmi 36 she began to 'feel fat' which I'd say was mostly that the fat was beginning to become more noticeable in everyday life. But she began to bike regularly around then, and if she was slow at first and struggled with hills it went fine. She began to really notice the heat more around that point, and had more problems with the legs of shorts riding up between her thighs when walking.
When she first hit her heaviest her walking had noticeably slowed, she had been a faster than average walker but if I unconsciously went my normal pace she had to ask me to slow down else she'd be out of breath quickly. Also having to step aside to let people pass sometimes. One flight of stairs was still no big deal, but two called for a few seconds break at the top to catch her breath. She began to have issues with some chairs.
No family really said anything, although who knows what they thought. I had one friend make a couple of comments to me about her size, but he's an ass like that in general.
In the years since then she's bounced up and down by twenty or thirty pounds a few times, always eventually getting back up to around that previous high. Now even at her heaviest she bikes at a pretty good clip and can handle substantial hills, and doesn't have to take a break after two flights of stairs. Strength/stamina caught up with the weight eventually I guess. A few more tries on skating and cross country skiing and those are both no goes still. Most people who know her now have only known her fat, so that is just who she is to them. Never any comments at jobs or school council or the like. A lot of stores carry up to her size now so clothes have gotten easier (although still not as easy as at size 14 or less).
FWIW I'm at BMI ~36 now, and last year I was still skating fine at BMI ~34 (although leaning over far enough to tighten my skates was tough), so I think her skating issues are not absolute with the weight. I can say that for me around bmi 34-35 I really began to feel fat, with more issues bending over, slowing in my walk, and just rubbing against my own body more (thigh on thigh, arm on side fat roll, belly on thigh, double chin on neck when looking down, etc). Occasionally I get annoyed or impatient at the limitation from this size, but I also love the softness and roundness, the occasional jiggles or feeling of my belly swaying. There are good things about being thinner, but for me at least there are plenty of good things about being fat too.
3 years