In addition, they’re often nutritionally incomplete and may be dangerous for certain people, especially without appropriate planning or medical supervision. Some of the same studies also revealed a significant reduction in markers of heart disease risk for those who lost weight using a VLCD . And if you’re underweight or nursing, it could actually cut out the fat and protein your body needs, Haas says. But if you have headaches, sinus congestion, fatigue, allergies, acne, joint pain or depression, you might benefit, he says. Johnson recommends that participants in her 14- to 28-day healthful-eating and detox challenges eat no more than three ounces of fish or meat twice a week.