Cleanses sometimes involve fasting or near-fasting, and that can actually have benefits, unless you have medical conditions or do it for too long. There is ample research demonstrating the effect of fasting on longevity; how fasting promotes autophagy, reduces mitochondrial oxidative stress, general decrease in signals associated with aging, and the potential to prevent and treat chronic illness , at least on some level. "Intermittent fasting" may be a viable option for those otherwise looking at specific cleanse diets. You basically limit eating to a few hours a day (typically around 8). That is a simple and sustainable way of eating, and doesn't involve buying cleanse products.