photo by Jonathan Pielmayer via Unsplash

To Fast or Fuel?

March 29, 2022

by tiffany ricci, rdn

Intermittent fasting is a popular trend these days. To fast is to abstain from food. The focus of intermittent fasting (IF) is to concentrate the amount of time you eat in cycles of fasting and eating. Several versions of this eating pattern abound - from fasting 16 hours a day to fasting for 24 hours once or twice a week. 

Intermittent fasting is popular and appealing because, unlike conventional diets that focus on what you can or cannot eat, IF just focuses on when to eat. Restricting the time you eat seems easy because the only decision to make when it comes to eating is - “Am I in my fasting window or not?” 

There’s no doubt that fasting is an important part of our regular digestive rhythm. Our bodies need to fast (abstain from food) so that they can focus on other important processes besides digestion. But, our bodies also need fuel during the active parts of our day. Skipping meals when you are most active - getting the kids off to school, exercising, starting your workday, running errands, etc. - can backfire, especially if you are a woman.

Women’s bodies are more sensitive to calorie restriction due to the menstrual cycle. The female hormonal response to fasting includes irregular periods, amenorrhea, infertility, and poor bone health. The hormonal fluctuations throughout the menstrual cycle can increase basal metabolic rate (the amount of energy your body needs to survive) and lack of energy intake to meet those increased needs can increase cortisol levels in the body. The severe energy restriction associated with intermittent fasting leads to poor outcomes for women. 

So, if fasting is good for you but you also need to fuel, how do you make this work? Fuel during the day. Fast at night. 

Fasting for 10-14 hours will provide just as much benefit, if not more, than the longer fasts of 16 hours or entire days without food. This allows your body to digest food before you sleep and then have energy on board for when you are most active - during the day. 

How do we do this? 

  • Stop eating 2-3 hours before you go to bed. 
  • Eat within 1-2 hours of waking. 
  • Make breakfast and lunch your biggest meals and dinner your smallest. 

Let’s create a sample fasting window: 

If you need to wake up at 6:00 am, then rewind 8 hours to set bedtime at 10:00 pm. Dinner should be done by 7:00 or 8:00 pm. Breakfast should be between 6:00 and 8:00 am.

The goal of this fasting protocol is to allow your body to fast at night while you’re sleeping to make the most of your sleep. By doing this, you can fuel your day when you are most active. Breakfast becomes a powerhouse of a meal to fuel your day. Dinner does not need to be the biggest meal because you are preparing for sleep. 

Of course, there will be days when you do not follow this pattern, and that’s okay. If you are consistent with the recommended schedule the majority of your days, you will see the sustainable results of this eating pattern. Our circadian rhythms appreciate fuel during the day because that correlates best with the activity level on a cellular level. 

When we view fasting from this perspective, the question is not an either/or - to fast or fuel; it’s both - to fuel your days and fast at night.

Never miss an issue, check out SLM's digital editions here!  

related articles: 

Get local updates, events and special offers!

Local Events