Even if I write about diet pills most of the time, I haven’t actually tried one for fear of potential side effects. But I can share my sister’s experience with diet pills. Iâ€™ve seen the side effects of diet pills in her. She could have achieved her desired weight, but she looks like a zombie with dark circles under her eye and her skin appeared dry because her drastic weight loss caused her skin to sag. She was conscious of her weight when she was in college so she tried diet pills without me and our mom’s knowledge.