For our next installment of Nutrition Plan Throw Down, we’re digging into the world of intermittent fasting, also referred to as IF, and exploring two popular methods. But before we dive in, let’s first understand what this diet is all about.


Intermittent fasting generally involves limiting the time you eat to a specific number of hours and fasting the rest of the day.  Seems fairly simple, but there are a number of popular ways to do it.


Why do some people fast intermittently?


According to Dr. Joseph Mercola, fasting has a number of health benefits, including improved cardiovascular health, reduced cancer risk, gene repair, and increased longevity. He also argues that it helps reset your body to burn fat for fuel. He also points to mounting evidence showing that when your body becomes adapted to burning fat instead of sugar as your primary fuel, you dramatically reduce your risk of chronic disease.


But IF is not for everyone! If you have chronic stress or cortisol dysregulation, fasting could make it worse. You should also avoid fasting if you are pregnant, nursing or have a history of disordered eating. Always speak to your doctor before trying out any new eating plan.


What does it do to the body?


Intermittent fasting essentially copies the eating habits of our ancestors, who would go long periods of time between meals. Thanks to grocery stores, refrigerators and GrubHub, we don’t HAVE to live that way anymore. Our Neanderthal relatives would go from feast to famine, and some recent research shows this is beneficial for the body.


  • It could normalize your insulin and leptin sensitivity to increase your energy.
  • It could help reset your body to use fat as its primary fuel.
  • It could regulate your hunger hormone.
  • It could lower triglyceride levels.


There are a few different popular intermittent fasting approaches. Let’s compare two of them side by side. And importantly, if you decide to try one of these IF programs, please talk to your doctor to make sure it is suitable for you.   


Type The 16/8 Method (Daily) The 5:2 Diet: Fast for two days per week Overall approach The 16/8 method is a daily approach to fasting where you fast for 14-16 hours. Each day you only eat between certain hours – usually 2-3 meals. For example, finish eating dinner by 8 pm and skip breakfast. Then dig into your first meal at 12. Voila! you’ve fasted for 16 hours between meals. The 5:2 Diet recommends eating normally five days of the week and fasting by only eating 500-600 calories for two days a week (not in a row).  Fast length The program calls for men to fast for 16 hours and women to fast from 14-15 hours depending on what works best for their bodies. Research has shown women do better with slightly shorter fasts which is why it’s only recommended to do it for 14-15 hours and extend the feeding window.  Two days a week only eat 500-600 calories, TOTAL. It doesn’t matter when you consume the calories, as long as you don’t go over.  Key to this diet – don’t fast on two consecutive days. So, fast on a Monday and Thursday or a Wednesday and a Friday (rather than a Monday and Tuesday, or Wednesday and Friday.) Feeding window 8-10 hours depending on your gender. Eat normally five days a week. On fasting days, your feeding window doesn’t matter as long as calories are restricted. Pros It’s simple to follow and easy for your body to adjust.  It’s a great way to cut back on mindless eating since you’ve restricted to your ‘feeding window.’ In the same vein, it minimizes late night snacking.  It usually helps with water intake – guzzle the H20 to help fight hunger pangs when it’s outside your eating hours.  It also is simple to follow (as long as you can count your calories on fasting days).  It’s flexible with when and how you take in your allotted 500 calories.  •	On fasting days, you can eat one big meal at 5 PM that’s 500 calories. Or you can space out and have 5 smaller 100 calorie ‘meals’ or snacks throughout the day. Or you can have a small 200 calorie ‘meal’ around 10 AM and another 300 calorie ‘meal’ around 5 PM. It’s totally up to you!  On fasting days, water intake also increases.  You can eat normally for five days a week, as long as you keep it healthy. This diet won’t work if you pig out five days a week and eat like a bird two days a week.  It’s easy to say no to temptation on a fasting day when you know you can have that same food the next day.  Cons You can eat whatever you want during your feeding period.  •	This could technically be a pro, but we’re going to go with a con because we believe what goes into your body matters, not just when you eat it. Healthy habits are important!  It doesn’t consider HOW much you eat.  Think about it, if you’re chowing down on fast food twice a day, you’re likely going to gain weight, rather than lose it thanks to the excessive calorie consumption. It’s easy to miss out on important nutrients. If you try this out, make sure your meals are well-balanced and you’re getting plenty of the good stuff. Like the 16/8 program, it doesn’t provide any guidelines on what to fuel your body with. Technically, you can eat whatever you want five days a week. Again, we’re putting this in the con section because we’re firm believers that quality food is critical!  5:2 Diet doesn’t consider HOW much you eat on non-fasting days. So, same thing with the 16/8 program, if you’re overeating five days a week, you’re not going to lose weight. Fasting days can cause headaches, so drink lots of water. It can be hard to work out on fasting days since calorie intake is so low.  This article is intended as informational, not promotional. In-Shape promotes healthy eating and encourages anyone to speak to their doctor before embarking on any type of eating plan.


Some people use an Intermittent Fasting Calculator to plan their IF diet.