The 5:2 Bikini Diet: Over 140 Delicious Recipes That Will Help You Lose Weight, Fast! Includes Weekly Exercise Plan and Calorie Counter. Jacqueline Whitehart
let it put you off your next fast day, which will probably be easier. On your next fast day, see if you can last longer without feeling poorly.
When not to fast?
There are certain medical conditions that would make fasting inadvisable or even dangerous, even in this more restrained form. Don’t attempt fasting if you are diabetic or pre-diabetic without seeking medical advice first. It is also not suitable if you are pregnant, breastfeeding or under 18 years old. If you are in any doubt, you must see your doctor first to discuss your options for dieting.
Those who are lucky enough to have good health and for whom fasting is a sensible diet option should also consider that there are some days that prove difficult for fasting.
If you’re already a 5:2er, you will already know that some fast days will breeze by while others will be hard. There have been a few times where I have chosen not to fast or given up on a fasting day halfway through. I don’t feel bad about this because I made the choice for the good of my short-term health and restarted the diet as soon as I felt better. Some of the things that have caused me to consider whether I should be fasting that day include a cold (it’s hard to fast when you have a bad cold, so my advice is: don’t fast), when I’ve had little or no sleep and possibly, for women only, at certain times of your monthly cycle.
Want to find out more about the health benefits?
Here are the studies referenced in this section. Be warned, most of it is not light reading, but it’s a very exciting field and could be worth the effort. Finally, this list is not exhaustive. This is because research in this field is booming and there are new studies coming out all the time. Look out for breaking news stories, which I believe will show more proof and more reasons to fast.
1 Parrella E., et al. ‘Protein restriction cycles reduce IGF-1 and phosphorylated Tau, and improve behavioral performance in an Alzheimer’s disease mouse model’,
http://www.scribd.com/doc/126262180/Longo-Cohen-Paper.
2 Mattson M., et al. ‘When a little poison is good for you’, New Scientist, 6 August 2008,
http://www.newscientist.com/article/mg19926681.700-when-a-little-poison-is-good-for-you.html.
3 Varady K., et al. ‘Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet Metabolism’, pp137–143, January 2013.
4 Alken J., et al. ‘Effect of fasting on young adults who have symptoms of hypoglycaemia in the absence of frequent meals’, European Journal of Clinical Nutrition 2008; 62: 721–726.
How to customize the 5:2 diet for you
Everybody is different: different weight, different height and different fitness. In this chapter we work out your Body Mass Index (BMI) and metabolic rate (BMR), which is how many calories you burn in a day. By calculating your BMI, we can set suitable and sustainable weight-loss targets. By working out your personal metabolic rate we can set a personalized calorie intake guide for the fast days, and, as we know, every calorie counts on a fast day.
Recently, there have been improvements to the way the BMI is calculated. This is because the old scale of BMI didn’t work very well if you were tall or short or more muscular than average; Brad Pitt, for example, at the time of Fight Club was very muscular and would have been considered overweight using the old BMI, so the new scale aims to be more accurate for everyone.
It doesn’t make much difference if you are relatively average, but if you are short it can make your BMI higher and if you are tall it can reduce your BMI a little. If you are tall, like me, it’s worth having a look at the new calculator – I dropped by 0.5 points from 21.6 to 21.1. But if you are average height it won’t make a difference.
The simplest way to calculate your BMI is to use an online calculator, such as:
http://people.maths.ox.ac.uk/trefethen/bmi_calc.html
• A BMI of less than 18.5 is considered underweight.
• A BMI of 18.5 to 24.9 is considered a normal healthy weight.
• A BMI of 25 to 29.9 is considered overweight.
• A BMI of 30 or greater is considered obese.
Personalized calorie allowance on fast days
While we use the standard numbers of 500 calories as a quarter of a woman’s normal daily calorie intake and 600 calories as a quarter of a man’s, we can in fact be far more accurate.
By calculating your Metabolic Rate (MR) you can work out your daily calorie needs. The BMR is how many calories your body burns when at rest.
First calculate your BMR:
To calculate your actual calorie needs to maintain your current weight, you just need to work out where you are on the exercise scale.
To work out the actual number of calories your body needs to maintain weight, multiply your BMR by the factor in the table above.
My maintenance calorie needs are:
I decide I am lightly active, so my multiplying factor is 1.375.
1414 × 1.375 = 1944 calories
I can also calculate how many calories I need to take in on my fasting days, as it is a quarter of this figure.
1944 ÷ 4 = 486 calories
So when I work out how many calories I am going to eat on a fast day, I need to make sure it is less than 486.
You should end up with the number of calories you need to eat on your fasting days. If you are like me, it will be slightly lower than 500 calories, but you might find you have a bonus of a few extra calories instead!
Don’t forget, if you lose a lot of weight, but find it slackens off after a while, you might need to re-calculate your calorie intake, as these formulas depend on your weight.
There is also one more thing that is worth considering: there are about 3,500 calories in 1lb of stored body fat. That means you need to reduce your calorie intake by 3,500 to lose 1lb in weight. That might sound like quite a lot, but if you think of it in terms of the restricted calorie days, a woman has a calorie deficit of (2,000–500) = 1,500 per day on a fast day, so will reduce her calorie intake by 3,000 over a standard 5:2 week. For a man this figure is increased to a 3,800 calorie reduction. This means that without doing anything else, a woman will lose just under 1lb a week on the 5:2 diet; a man, just over 1lb.
Taking into account the level of exercise and healthy eating on non-fast days, then we are looking at an even greater weight loss. This is simple maths and doesn’t take into consideration