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When Not To Fast

Fasting, Intermittment Fasting, When Not To Fast, Health, Nutrition, Nutritionist, Dietitian, Functional Medicine

When Not To Fast

Ahhh, fasting is quite the thing to do nowadays. But, I want to talk to you about when NOT to fast. When is fasting not ideal? Fasting does have benefits, but some people aren’t ready to make the leap to fasting 15+ hours. It’s something they have to work towards or they simply are not in the right season.

When Not To Fast

Let’s hop right into the top reasons on why you shouldn’t fast. Heads up: I’m not talking about the normal 12 hour fast from not eating after dinner to eating in the morning, I’m talking about long extended fasts where you might be skipping whole meals.


This is a pretty obvious one because we need all the fuel during this season of life! You’re growing a new human – that takes a lot of resources, so you want to ensure that you’re intaking enough for mama + baby. Long term fasting isn’t recommended for breastfeeding because it can affect milk supply. Your milk supply can dip due to lower calories and nutrient levels could end up being subpar. We want #nutrientdense milk, am I right?!

Severe Blood Sugar Swings {Diabetes/Insulin Resistance}

While fasting does have studied benefits for diabetes, it totally depends on the state of the individual if long term fasting is okay. I find that a lot of clients we work with that have blood sugar imbalances feel best with consistent regular balanced meals versus skipping meals. Your body will get glucose into the bloodstream from somewhere – whether you eat it or use cortisol (stress hormone) to tap it out of your liver and muscles – it will come from somewhere.

These blood sugar swings can throw you into fight or flight and cause more issues and make you feel low blood sugar symptoms. We don’t want someone to go through low blood sugar dips. When blood sugar is a little bit more in control, if you want, you can try fasting!

High Stress/Adrenal + HPA Dysfunction

As stated above, fasting can naturally be a little stressful because it’s going to pump out cortisol to maintain your blood glucose when you don’t eat. This cortisol release can send you into fight or flight mode and cause anxiety. So, if you have pre-existing adrenal issues, you probably don’t need an additional worry. I found a meta-analysis that looked over many studies to find connection between adrenals and fasting and found…

 Overall, caloric restriction significantly increased serum cortisol level in 13 studies (357 total participants). Fasting showed a very strong effect in increasing serum cortisol.


Anyone Under 18 {When Not To Fast}

Anyone who is a teenager and younger is in a massive growth phase! Teenagers and younger do NOT NEED to be restricting as their body has hormone and growth demands. Many younger kids are very active as well and need the fuel and regularly timed meals.

A Woman Who Has Irregular Cycles

If a woman is having irregular cycles, there is usually an underlying cause. This is a time when not to fast. We see irregular cycles happen when there is too much caloric restriction, adrenal issues, blood sugar issues, thyroid, and more. Sex hormones tend to be downstream, which means there is a lot that is happening beforehand to lead to having irregular cycles.

Fasting is not the solution here.

History of Eating Disorders

Long-term fasts can be very triggering for someone who has a history of eating disorders. It can be restrictive and can move them backwards in understanding how to fuel their body + getting enough fuel for the body. We do not want to send them into a spiral as they are in recovery!

Are you in one of these categories + you’re wondering what there is to do if you can’t fast? Reach out to our team of dietitians and book your free call to get set up with our programs to help you start navigating your diet + life to start feeling your best!

Lahana Vigliano, CCN
Avatar for Lahana Vigliano
Lahana Vigliano

Lahana Vigliano is a Certified Clinical Nutritionist and CEO of Nuvitru Wellness. She has her Bachelor's Degree in Nutrition Science and Masters Degree in Nutrition Science and Functional Medicine. She is currently pursuing her doctorate degree in Clinical Nutrition. Lahana and her team help support women who struggle with weight loss, hormonal imbalances, digestive issues, chronic fatigue, and many other lingering issues that leaves women not feeling their best. She uses food as medicine, as well as herbs and supplements when needed, to support her clients. She looks at the whole body holistically making sure women are understanding how nutrition, sleep, stress, and their environment impact their health. Connect with her on Facebook + Instagram (@nuvitruwellness).