How Many Calories Should You Consume on a Fast Day?

My wife Lisa made a great point yesterday in the Facebook Group and I wanted to share it here.

“I’ll be honest. I never ate breakfast until I got pregnant. Since then that has been the hardest thing to go without! I do eat a small breakfast- and alternate depending on weather: portable oatmeal, a banana, yogurt ( something with less sugar, I like Siggi’s ), a smoothie, handful of almonds and walnuts, or a Breakstone’s cottage cheese ( with pineapple). This has helped me on Mon & Thurs. As a woman who needs additional calcium, this helps me get it.”

When I started this program, she was supportive and I encouraged her to try it too. She didn’t at first, but as you can see from her post above, she eventually dipped her toe in the pond with a few modifications that made it work for her.  Now we both enjoy our lifestyle of Intermittent Fasting. While we both do it slightly differently, Mondays and Thursdays are calorie restriction days for both of us, and it makes it easier to do it together!

The bottom line is – don’t feel like 100% compliance is required. Anything you can do to restrict your calories a couple days a week is going to help. Some people can jump right in, but some need to adjust more slowly. Don’t feel like a failure if your first Fast Day didn’t go perfectly – mine didn’t either! If you are trying 8/16 and you just can’t make it until lunch – start by making it until 10:00am, then 10:30…then 11:00 etc.

If you are considering trying the Fast 5/2 days but think the 600/500 calorie restriction is a bit too much, here is some good news!  First, the 600/500 is based on 25% of the “average calorie requirement” of 2400/2000 for a man or woman. But you might not be average!  Head over to and calculate how many calories you need to burn daily.  For example, when I punched in my height, weight, age and activity level, I got 2730 – that’s with light activity level (exercise 1-3 days a week).  Normally I would say moderate (5 days) but with it being so cold here lately, my walks have been less frequent and shorter. Still – 2730/4  = 682.  That extra 82 calories lets me sneak a glass of wine in with dinner.

I and many others have had success with the 600 calories for men / 500 calories for women limits, but many other Intermittent Fasting programs have 800 calorie limits. If you just can’t make the 600 happen, consider increasing your amount a bit on Fast 5/2 days, but try eating Mediterranean or backing off the carbs on most other days to offset.

Remember, don’t be obsessed with perfection on Fast Days.  Track and measure with MyFitnessPal, but if you end up with 700 calories, don’t beat yourself up – you still had a great low calorie day!  Whatever you do, don’t decide “Well  I’m not going to hit my calorie goal so I might as well eat those cookies!” NO – just do your best today and you will still make progress towards your new habit/lifestyle AND reap the health benefits of a good Fast Day.  When it comes to the cookie…”There is always tomorrow!”

If you have  not joined the Facebook group yet, click the link over to the right and jump on in – we’re a friendly bunch and we’re here to help!


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