When to Fast and Not to Fast on the 5:2 Diet

Before you start the 5:2 Diet or any other fast, make sure you talk to your physician or health professional about fasting, its benefits and drawbacks, and the status of your health.

What days and times to fast

The 5:2 Diet prescribes two days of modified fasting and five days free from calorie counting. When deciding which days during the week to fast, understand that you may have to be flexible. What worked for you last week may not, due to social engagements or other obligations, work for you this week.

The key is to choose two nonconsecutive days in which to fast. So for example, if you fasted on Monday, don't fast again until Wednesday or later in the week, giving you at least one full day between fasting periods.

By choosing nonconsecutive days, you won't feel emotionally deprived of food and, thus, have a better chance of sticking with the program long-term. The 5:2 Diet is aimed at doing away with the feelings of deprivation, anxiety, and guilt that come with so many mainstream diets.

Fasting, no matter the method that you choose, isn't a traditional diet; it's a lifelong behavioral change, and the longer you do it, the easier and more fulfilling it will become.

If you decide to fast on a Monday and a Thursday one week, you now just have to decide how long you'll fast for. You'll optimally fast for 16 hours at a time, which has been found to be the sweet spot in fasting — you get the full benefits of a longer fast without the difficulties of completing a longer fast (compared to a fast that goes on for 24 hours or more).

But doing so may be challenging with the 5:2 Diet because you break up your caloric limits between breakfast and an evening meal.

However, you may find it easier on your fasting days to get all your calories in one meal. It's really up to you. The key is to play around with the fasting method of your choosing, but remember, stick to one particular method for three months before you try another one.

Three months is the sweet spot when it comes to giving your body a chance to respond to the fasting method of your choosing and really seeing results from it.

Who shouldn't do the 5:2 Diet

Some people shouldn't fast on the 5:2 Diet, including the following:

• Pregnant women: More research must be done to determine whether or not fasting is safe for pregnant women, and until scientists prove that fasting is healthy during this time of your life, don’t fast.

• Children: Because children are still developing physically and mentally, they don't need any nutritional stresses.

  Although the occasional fast helps decrease the levels of IGF-1 in adults (which helps to promote overall health and longevity), during the formative childhood years, humans naturally have higher levels of IGF-1 to help them grow and develop properly. Never encourage fasting in anyone under the age of 18.

• People with medical conditions: If you have any underlying medical conditions, such as HIV/AIDS, cancer, diabetes, or an eating disorder, fasting probably isn't a wise choice.

If you're a reasonably healthy adult looking to lose some body fat, feel revitalized, and live an all-around healthier lifestyle, then the 5:2 Diet may very well be a viable option for you.

More information on the 5:2 diet.