I've been working in retail for about two years now, and nothing breaks my heart more than seeing girls and guys start crying in the dressing room because they've gone up a pants or shorts size.
It breaks my heart even more that they're crying over something that in reality, doesn't define who they are or even their size.
Each individual has a certain pants and shirt size that they generally fit into since, usually, these sizes are dependent on our waist and height. When going into fitting rooms, we grab these sizes of ours without even thinking, no matter what store we walk into.
Then, we panic. The jeans don't fit our thighs, the waist might be too loose, or maybe the waist doesn't button at all. We all wonder how it could've happened. We start thinking about our diet or how much exercise we did that week.
The problem with this? Nobody actually blames the jeans themselves.
From personal experience, I know that jean size depends completely on what brand of jeans they are. Where I work, they are constantly changing the type of material the jeans are made out of. If the jeans you are trying on are made out of a material that is more stuff than stretchy, your jeans size is more likely to be a bit higher than you're used to. However, some stretchier materials cause the size of their jeans to be tighter when first bought since they stretch out over time. There are also many different types of jeans, such as skinny or flare. This could greatly impact how they fit.
Another huge factor on jean size is muscle. Personally, I have more leg muscle since I'm a dancer. This causes my jean size to be a bit larger than my waist. Some may have a larger or smaller backside than others, which could also cause them to have a larger jeans size than their actual size looks to be.
Whenever I see someone upset about their jeans size changing, I always am sure to tell them to think of it more as a range than one specific size. It is a much healthier way to think of it, and it could help you think of jeans size as something that doesn't matter anymore. Your jeans size is not a defining feature of your body. No matter how small or large it may be, it is not specifically telling of your body shape.
So next time you're shopping, remember: You're perfect the size you are. It's what makes you unique. Sizes are not important.