Intermittent fasts, are they worth it?

Today is Shrove Tuesday, also known as pancake day, a day where you delve into your cupboards and eek out all the best foods you have and eat them before Easter. Historically these foods were flour, eggs, sugar and milk, which is where the idea of pancakes came from. The period between now and Easter is called lent which Christians believe to be a solemn period of reflection and commonly amongst the most faithful, a period of fasting. Popular culture has left it being a time to give up cigarettes, or alcohol or chocolate, but what about fasting specifically for weight loss, what are the implications on body composition and health?



Intermittent fasting is a really trendy diet at the moment, however like all diets it has drawbacks. For most people I wouldn’t recommend it, but there are exceptions if done correctly. In this article I am going to lay out the advantages and drawbacks and then leave you the reader to think if it is a good idea.

Advantages

Firstly, irrespective of whether you choose a long fast, lots of short fasts or maybe even one a month, the mechanism which allows a fast to be effective is that when you want to lose weight you need a calorie deficit. Fasts do this very well, as the whole time you are fasting, your energy balance is negative. Exercising in this state will increase the deficit further and allow you to lose even more.

Studies on rodents have shown that it is possible that calorie restriction will help you live longer and avoid diseases.

Thirdly fasts are easy to follow, one day a week you eat nothing but tea, and then the rest of the week you eat what you like. There are no lifestyle changes or anything like that and you lose weight.

Disadvantages

My first point of this section follows straight from the last, it is too easy. Realistically the majority won’t fast one day a week for the rest of their lives. The problem with all diets which focus on just calorie deficits is that you have a stark choice, stay hungry or get fat.

Body composition is more about what you eat than when you eat. If you gave a woman a 2000 calorie diet of chocolate and another a 2000 calorie diet of lean protein and vegetables which one do you think would have a healthier body composition? This is an exaggerated analogy but people who fast feel justified in eating poorly the rest of the time.

The key to staying lean for life is in developing a method of increasing your metabolism for life and by the far the best way to do that is by increasing muscle mass. This requires regular feeding, sure you can reduce loss or even maintain muscle mass on a calorie deficient diet like fasting with resistance training, but this makes fasting very short sighted.

Fasting alters your hormone balance, leading to; lack of lean tissue, chronic fatigue, sleep disorders, inflammation, sleep problems and infertility.

So yes, fasting is a tool which can be used under the correct circumstances, and yes it does help to lose weight, but it is not a realistic change to make for the long term. I believe that you have to earn the body you live with, quick fixes are great but they need to have been achieved through discipline, hard work and sustainable principles which benefit your health for the long term.

Refs

Halberg, N, et al. Effect of intermittent fasting and refeeding on insulin action in healthy men. Journal of Applied Physiology. 2005 99(6) p2128-36

Klempel, M, et al. Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women. Nutrition Journal. 2012 11(98)

Martin, B, et al. sex dependent metabolic, neuroendocrine and cognitive responses to dietary energy restriction and excess. Endocrinology. 2007 148(9) p4318-25


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