Crash diets may harm your heart Cardiologist Isadore Rosenfeld, MD, a professor of clinical medicine at Weill Cornell Medical College, in New York City, and author of the forthcoming "Doctor of the Heart: A Life in Medicine, " opposes crash diets (less than 1, 200 calories a day) and detox plans like the Master Cleanse. The Master Cleanse involves consuming a mixture of water, lemon juice, maple syrup, and cayenne pepper -- and nothing else -- for several days. Research suggests rapid weight loss can slow your metabolism, leading to future weight gain, and deprive your body of essential nutrients. What's more, crash diets can weaken your immune system and increase your risk of dehydration, heart palpitations, and cardiac stress. If you're overweight, slimming down is critical for your overall health. Even moderate weight loss can lower your risk of developing heart disease, diabetes, and some types of cancer. Bariatric surgery may be beneficial for selected patients. you may reach for best surgeon in Hyderabad, India. It's important to lose weight safely, which usually means slowly: Most experts recommend dropping just 1 to 2 pounds a week. And despite what some brand-name diets claim, the best way to do so is to exercise regularly and stick to a diet that limits saturated fat and sugars and emphasizes fruits and vegetables, lean meats and fish, and whole grains.