The smart way to fast on the Fast Metabolism Diet

Religious holidays prompt questions about fasting from some of our readers. But religion isn’t the only time you might need to fast. Certain medical tests and surgeries also require a period of fasting. Any kind of fasting can be tough on your metabolism, but here’s how to meet your fasting obligation, while minimizing the impact on your metabolism.


No matter why you’ll be fasting, you want your final evening meal to be full of high-quality foods that stick with you, stabilize your blood sugar as much as possible, and calm your hormones.

Remember when fasting, do not alert your body to store fat by stressing about it.  You want to remain calm and find peace in the purpose of your fast.  The meaning of it can be sacred or medically necessary.  And there’s no need to gorge yourself before a fast.  It will only stretch your stomach and put you into storage mode.

I like to think about the powers of 3 in the body.  You can go without water for about 3 days, without food for about 3 weeks, without air for about 3 minutes and survive in extreme conditions for approximately 3 hours.  For a short fast, your body will be perfectly fine!

Here are some fasting tips you can use.

The night before

No matter what phase you are on, go for a Phase-3 type of meal. Include a lean protein, healthy fat, and lots of vegetables. But instead of the grain you might normally eat with a Phase 3 dinner, substitute a starch like sweet potato or legumes. You’ll still be getting adrenal-calming carbs, but the fiber in these starchy foods will stabilize your blood sugar and lengthen the delivery of those carbs, making you feel full longer.

Also, add a fruit to your meal. This will provide some natural sugar, calming to your hormones. Go for low-glycemic fruits like berries.

This type of complete meal will give your body lots of slow-burning nutrition to carry you as much as possible through your fasting period.

As for hydration, be sure to drink plenty of plain water the whole day prior to your fast. Try to stick to plain spring water, which has the best electrolyte balance among types of water.

During your fast

If you are allowed to drink water during your fast, then continue to drink your usual amount.

Some fasts, such as the Catholic Lenten fast, are modified fasts that do allow foods. Catholics observing Lent on Ash Wednesday and Good Friday may consume one full meal and two snacks during the day. Consider a morning snack that’s protein-based, such as a hard-boiled egg, or a few slices of smoked salmon with some vegetables. Then take your balanced main meal (protein, vegetable, grain, healthy fat) around mid-day or a little later. Follow with a late-afternoon snack of protein/fat, like raw nuts, plus a veggie.

Muslims celebrating Ramadan fast completely during the daylight hours, then consume the day’s meal at sunset. Before sunrise, consider a balance breakfast, the in the evening, a similar balanced meal.

After your fast

If your fast is quite long, such as the day-long fast for the Jewish holiday of Yom Kippur, your body will be fairly depleted 24 hours later. But it’s important not to overdo your first meal. Your digestive system at this point will be sensitive, so it’s important to treat it kindly.

For your first meal after a long fast, try eating a Phase 1 breakfast (even if you are supposed to be on a different phase of the diet). Go for Irish oatmeal or a quinoa porridge, or even soft brown rice. Add cinnamon or nutmeg, and stevia for flavor, and add a fruit, such as strawberries, or blackberries.

Then for your next meal, you can resume with whatever meal and phase you  were on before your fast.

For shorter fasts, such as the 12- or 15-hour fasts you’re often required to perform when undergoing certain medical tests, you’ll be able to break your fast with whatever meal you would normally have at that time. However, if your stomach is feeling sensitive, as it can after certain tests, stick with the easy-to-digest Phase 1 breakfast-type meal. Then resume with your correct meal/phase for the next meal.

Be sure to drink lots of plain water to keep your body hydrated and your liver running smoothly.

Involuntary fasting

You can easily find yourself in a situation where you didn’t intend to fast, such as the flu or another “bug” that leaves you with no appetite, or worse — the inability to keep anything down. Try to drink plenty of water, even if you’re unable to eat. When you start to feel better, stick with those calming, easy-to-digest Phase 1 grains and fruits that will give you quick energy, yet be easy on the stomach.