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How does fasting affect the body?

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Fasting can have a variety of effects on the body. These include:
  • modest but temporary weight loss: The pounds usually return once you go back to your normal diet
  • improved heart health, though this area of research needs more study
  • improvements in certain medical conditions, notably rheumatoid arthritis, though the benefits fade over time
Fasting also can have some serious negative effects on the body, such as:
  • dizziness
  • headaches
  • fatigue
  • fruity-smelling breath
  • changes in heart rhythm
Fasting for long periods can have serious health effects. Do not fast without a doctor's supervision.

When you fast, your body is deprived of the nutrients, proteins, and other typical sources of energy provided by food. In order to find those nutrients, your body taps into the glycogen that you have in your muscles. After the glycogen is used up, your body will eat away at fat. Also, because you are eating less, your metabolism will slow down.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.