Does Intermittent Fasting Work?

November 19, 2018



My blog ideas seem to start with some form of education session during the day job. Particularly in type 2 education. We get quite a mixture of patients from the rather ambivalent to highly engaged. Some are so engaged they look into various diets to help them manage their condition. Sometimes with tremendous success.


One of the more popular diets I encounter is the intermittent fasting diet. This is likely common because it gets so much media attention. Michael Mosley in particular has made such diets extremely popular and specifically positions them for type 2 diabetes management. 


A very quick google is abundant with websites on intermittent fasting and it’s benefits. But does it actually work? 


Today I am going to look at the evidence behind intermittent fasting and whether it’s a diet you should be following. 


What is intermittent fasting? 

There is no true system of intermittent fasting. The principles is based on two systems. Either reducing the amount of calories you eat on some days or only eating during set times of the day. 


The research has focused on 3 main types. Alternate day fasting involves eating nothing one day followed by a habitual diet the following day. Modified fasting is the most common and popular. This system involves eating less on certain days like the 5:2 diet. Finally, time restricted fasting refers to only eating during specific hours of the day. However, technically you could go rogue and implement this method in any format you wish. 


This is in contrast to typical healthy eating advice. This usually focuses on continuous energy/calorie restriction. 


What’s the proposed benefit? 

The theory behind intermittent fasting is it allows the body tap into it’s fat stores allowing you to lose weight. Also, by reducing the amount or time you eat, you will have fewer calories. 


Further to this it is claimed intermittent fasting improves hormone sensitivity, can increase satiety,  reduces inflammation in the body, improves cellular repair, improves gut microbiota and reduces lipids in the circulation. 


Quite the claims. 


Does intermittent fasting work? 

When compared to control groups it does seem beneficial. When we say control groups, we mean a group of people who did nothing. So we have a baseline measure. 


One study I read also proposes an interesting insight into the time restricted method. This study proposed eating during certain hours which match our natural circadian rhythms has more favourable outcomes on health. 


This study was conducted in rodents and looked at two groups. One group was fed at different times throughout the day and night. The first group developed obesity and became metabolically dysfunctional. The second group was fed the same calories but only during an 8 hour period. Group 2 was protected from obesity, fatty liver and higher insulin levels. 


Should I be following an intermittent fasting programme?

Although research into intermittent fasting is promising, it shows no extra benefit of traditional dietary methods. In fact, every article I read showed comparable outcomes between intermittent fasting and continuous calorie restriction. 


This is still significant because it is as effective as other diets. Therefore, if such a method works for you and you are able to stick with it, it could be a great option for long term success. 

Evidence for the long term effects is missing at present. 


Also, most of the research conducted to date has focused on rodents, religious fasting or has less than 50 participants. In other words, it’s hardly robust evidence. When data is lacking it’s hard to say whether more data will show more or less benefit. 


Animal studies in particular often struggle to be applied to humans. Even if the findings apply to humans physiologically it can be difficult to replicate in humans. Tests in animals can be completely controlled. In other words, we feed them what they want and they can’t do a thing a about it. 


Humans on the other hand tend to be a bit more picky. Particularly outside of the lab environment.  So even if something works in a study, once we’re back in our normal lives surrounded by temptation and every day stress, things are slightly skewed. 


Why so much media attention?

People like a gimmick. In this case the gimmick does work just as well as any other diet in the short term. However, selling healthy eating and exercise isn’t quite as sexy as a shiny new diet. 


It also helps prominent journalist in Michael Mosley has produced many books on the matter and has good exposure on the BBC. This gauges media and public interest which then fuels itself. 


Ultimately, it seems the best diet is one you can stick to. Of course, this is assuming it is safe and doesn’t cut out major nutrients from your diet. This may be true particularly if you are someone who would find it easier to be strict on certain days and slightly more relaxed on others, this could be for you. 


Consistency is key on any diet.  So if you do join the intermittent fasting trend I would strongly advise to make sure you’re prepared to stick with it for the long term. 



Ultimately, intermittent fasting achieves the same as other diets on on the market. Intermittent fasting might be a useful method for dieting if it works for you. The concern would be not many diets show long term success and this may well fall into that category. Time will tell. 


It is comparable to continuous calorie restriction in terms of weight loss and health outcomes. Those that struggle to regularly control their intake and would rather set aside specific times of reduced eating might benefit from this. 


If taking medication it is wise to speak with your healthcare team before significantly reducing your calories on certain days to prevent ill effects. 




Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials


Dietary Interventions for the Prevention of Type 2 Diabetes in High-Risk Groups: Current State of Evidence and Future Research Needs



Effect of intermittent versus continuous energy restriction on weight loss, maintenance and cardiometabolic risk: A randomized 1-year trial.


Intermittent energy restriction in type 2 diabetes: A short discussion of medication management


Intermittent fasting and human metabolic health


Intermittent fasting interventions for the treatment of overweight and obesity in adults aged 18 years and over: a systematic review protocol.


Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis.


Impact of intermittent fasting on glucose homeostasis.


Impact of intermittent fasting on the lipid profile: Assessment associated with diet and weight loss


Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings.


Metabolic Effects of Intermittent Fasting


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