The Dark Side of Fasting (and Intermittent Fasting): Dr. Berg Explains

Today, let’s talk about the benefits and dangers of fasting.

Some of the top benefits of fasting include weight loss, cognitive improvements, and enhanced heart function.

Most of the dangers of fasting I’m going to cover aren’t related to a 16 to 18-hour fast. This applies more to prolonged fasting, which is when a person fasts for 48 to 72 hours—or even longer.

The purpose of eating is not just to get fuel. It’s also to get nutrients. When you’re fasting, you’re restricting nutrients. If your diet isn’t providing you with the nutrients you need when you do eat, you could end up with deficiencies that lead to certain issues.

It’s crucial to do a prolonged fast correctly and avoid common mistakes related to the dark side of fasting.

The dark side of prolonged fasting:

1. Refeeding syndrome

When you come off of a fast, have a small amount of food, wait a couple of hours, and have a little bit more. Avoid overeating or eating carbs.

2. Dirty keto

Make sure you consume nutrient-dense, high-quality foods on the keto diet.

3. Not taking nutrients while fasting

At the bare minimum, you need to take electrolytes, sea salt, trace minerals, and B vitamins while fasting.

4. Kidney stones

Avoid high-oxalate foods if you’re prone to kidney stones. Also, consume at least two and a half liters of fluid a day, and add lemon juice to your water. When you’re back to having meals, consume large salads.

5. Anorexia

Anorexia will cause nutritional deficiencies. Instead of fasting, get on the keto diet.

6. Athletes that have not adapted to fat yet

Give your body enough time to become fully fat-adapted before attempting prolonged fasting.

7. Fasting for children

Fasting isn’t a good idea for children. Eating three meals a day and cutting out snacking may be beneficial for children. Teenagers who are overweight may consider two meals a day without snacking.

8. Not getting enough nutrition while pregnant or lactating

Not getting enough nutrients while pregnant or lactating can lead to issues for the mother and child. Choosing a whole-food, natural prenatal vitamin over a synthetic prenatal vitamin is also important.

9. Muscle loss

If you’re older and noticing muscle loss, try adding a blend of amino acids to your diet.

10. Ketoacidosis

This rare condition occurs in people under very specific circumstances and isn't something most people should be concerned about.