Common myths about nutrition and fitness include the belief that carbohydrates are inherently bad, that all fats lead to weight gain, and that supplements can replace a balanced diet. Many also think that strength training will make women bulky, which is untrue; it actually supports a toned physique. Another myth is that exercising on an empty stomach burns more fat, while in reality, proper nutrition enhances performance. Debunking these myths is vital for informed health decisions and achieving fitness goals.