Weight loss is something that must be done gradually, because when pushed to the extreme, the body has its own sweet ways of hitting back with more force. When you go on a sudden diet and stop eating food, the balance that your body maintains in its bile salts will be affected. Your cholesterol levels will also be affected due to this sudden shift. Hair loss is yet another side effect that occurs during weight loss. When you go on a diet, the protein content in your food is bound to come down, and this will cause hair loss. People who take diet pills are prone to heart palpitations and fluctuations in the heart rate.