A year ago, when a friend told me she planned to lose weight by doing the Master Cleanse, I didn’t think much of it. That is until I watched her mix a not-so-enticing concoction of water, sea salt, maple syrup, cayenne pepper, and lemon juice. “This cannot be healthy,” I told her. She ignored my concerns. I tried to convince myself that she wouldn’t stick with it long enough for it to make her ghastly thin, or worse, ghastly ill. After one week of only this detox mix, she gave up—5 pounds lighter and, in my opinion, slightly grayish in skin tone. I still don’t think these detox plans are safe. And apparently, neither do experts.

The plans are supposed to remove chemical and dietary toxins from the body, but weight-loss experts say there is no scientific evidence such programs do a better job than the body's own organs, reports USA Today. They also say many of the plans are deficient in protein and other nutrients. “These kinds of diets are not a reasonable approach to weight loss, and there is no data that they do what they claim,” says Gary Foster, director of the Center for Obesity Research and Education at Temple University in Philadelphia. He is concerned that these cleanses could be harmful to people who suffer the medical consequences of obesity, such as high blood pressure, diabetes, and heart disease.

In a recent report on detox plans, we looked at the evidence, or lack thereof, and concluded that fasting for a day or so is generally not harmful and might shake you out of an unhealthy eating pattern. But detox diets often involve severe caloric restrictions for a week or more. And while some focus on fresh produce and whole grains, others drastically limit the foods you eat. Such diets can lead to nutrient deficiencies, blood-sugar problems, severe diarrhea, nausea, and fatigue.

Look for safer, more healthful ways to lose weight. Take a look at our six secrets of the slim, find a diet that works best for you, and check out recent research on cutting calories.

—Ginger Skinner