In the first couple weeks of intermittent fasting, you may experience these not-so-fun side effects:
- Headaches
- Fatigue and low energy
- Inability to concentrate
- Irritability (feeling hangry)
- Feeling cold
- Nausea
- Insomnia
- Hunger
Fasting will be challenging for the first four to seven days because of these annoying and uncomfortable side effects, and maybe even for longer, but Dr. Fung told POPSUGAR that your body quickly adjusts.
After the first week or two, your mind will feel clear, you'll likely have more energy and improved sleep and digestion, you'll actually feel less hungry, and you'll look leaner. So hang in there! If you're still feeling these symptoms after a few weeks, talk to your doctor.
If at any point these symptoms feel debilitating (i.e. if you feel like you're going to pass out or are so hungry you can't concentrate at work), try adjusting to another IF method, such as a shorter fasting window. Otherwise, IF may not be for you — and that's OK! Every body is different.