How else are you supposed to lose weight? If you cut back on the amount of unhealthy foods you are consuming, and eat smaller portions, then there's no problem. You'll get thinner. Simple as that.

this point isn't very specific. I could start a diet with a goal of losing 20 pounds in 20 years. Your daily consumption would barely change, yet it would still constitute a "diet". Whether more extreme diets like Atkins are detrimental would make a more pointed debate.