You might think that complimenting someone on losing weight is as harmless as commenting on their cute new do, but that's not always the case. This video from BuzzFeed explains that you never know what's behind weight loss—it might be completely unintentional, or due to unhealthy habits or a painful experience like a breakup. Even if you mean well, praising someone for losing weight could have a negative effect. You're often better off telling someone you like their outfit or simply their smile.

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