This is from a study done by Harvard and UNC
Time laid out the exact methodology:
Out of 646 people surveyed, 70% could recall a humblebrag they’d heard recently.
Next, they established that there are two distinct types of humblebrags. The first falls back on a complaint (“I hate that I look so young; even a 19-year-old hit on me!”) while the second relies on humility (“Why do I always get asked to work on the most important assignment?”). About 60% of the humblebrags people remembered fell into the complaint category.
The researchers then carried out experiments to see how people responded to humblebrags, with a particular focus on the bragger’s perceived likability and competence. They found that regular bragging was better on both counts, because it at least comes off as genuine.
Here's the truth. If you're going to brag, just brag - just come right out with it. Because doing the "I don't know why I always look this tan.. " makes people hate you.