My Times piece on intermittent fasting

Last Saturday the Times here in the UK published a piece I wrote about ‘intermittent fasting’. This topic has been getting a lot of press of late (the Daily Mail, for instance, carried a piece earlier this week too). I’m pleased to see that intermittent fasting is getting some attention, and there’s some challenge to the ‘3 meals a day’ mantra that I, until recently, subscribed to myself. Intermittent fasting is not for everyone (see below), but I’ve seen it help people control their weight and improve their wellbeing. I’ve also met lots of individuals who eat quite erratically and have believed that they are harming themselves doing this, look at their eating habits in a new and healthier light.

Why Fasting is the New Way to Lose Weight (and Live Longer)

“Eat three meals a day” has been part of dietary and weight loss dogma for decades. However, recently, there has been growing interest in what is known as ‘intermittent fasting’, the practice of food restriction that may involve extended periods, sometimes whole days, without eating. While intermittent fasting appears to contradict an essential credo of healthy eating advice, there is evidence that it can enhance body composition and health and may even extend life.

While eating is undoubtedly essential to life, it has inherent hazards too. For example, when we eat, we secrete the hormone insulin which facilitates the uptake of nutrients, including fat, into cells. In general terms, the more insulin we secrete, the fatter we get, and the more likely we are to become ‘numb’ to the effects of insulin over time too. This situation, termed ‘insulin resistance’, can lead to a ‘starving’ of the cells, provoking symptoms such as fatigue and hunger. Insulin resistance is also a potential driver of chronic diseases such as heart disease, Alzheimer’s disease and type 2 diabetes.

Quelling insulin will help protect against these conditions, and will facilitate fat loss too. One way to quell insulin levels is to eat a diet largely devoid of the foods that cause surges in blood sugar such as those added sugar as well as starchy ‘staples’ like bread, potatoes, rice pasta and breakfast cereals. Another way, though, to moderate insulin levels is to extend the time between eating. This, in essence, is what intermittent fasting is about.

Intermittent fasting experiments in animals has found improvements in markers for disease, including improved insulin functioning, as well as enhanced brain health. There is some encouraging human research too. In one study published last year, overweight and obese women undertook daily or intermittent caloric restriction over a 6-month period [1]. Half the women restricted food intake to 1,500 calories a day. Those on the intermittent fasting regime, on the other hand, ate 650 calories on each of two days each week, and were free to eat as much as they liked the rest of the time.

Both groups lost similar amounts of weight (an average of about 6 kg), and also saw improvements in measures such as blood pressure and inflammation. Insulin levels fell and insulin functioning rose in both groups too, but it did so more in the intermittent fasters. Another potential benefit of intermittent fasting is that, compared to daily caloric restriction, it appears to help preserve muscle mass during weight loss [2].

How to do it

One type of intermittent fasting is known as ‘alternate day fasting’. In essence this means having food-free days alternating with days of unrestricted eating. Other forms of intermittent fasting include contracting the ‘window’ available for eating each day to, say, 4-8 hours. For many, these approaches are impractical and simply too arduous. The good news is that less extreme and more realistic versions of intermittent fasting can reap significant dividends.

One approach could be to extend the period of low insulin typically seen at night. An early dinner or delayed breakfast will do this. As the body becomes more accustomed to lower insulin levels, its ability to mobilise fat will be enhanced. This fat provides fuel for the body, and is a potential source of sustenance during extended periods without food. Once the body is more adept at burning fat as its primary fuel, it’s less reliant of food for fuel and energy. When the body ‘feeds off its fat’, one’s ability to go without food and not suffer undue hunger, fatigue or issues with brain function is enhanced. I’ve seen many individuals who, after several weeks of low-carb eating and some experimentation with intermittent fasting are amazed at the length of time the can go without getting unduly hungry or experiencing and loss of energy or drop in mental functioning.

Once the body is better adapting in this way, the next step might be to drop some breakfasts or dinners altogether. My advice would be to drop the one you feel is going to be easiest to do without. If you’re generally hungry in the morning and find your appetite tails off at the end of the day, then dinner is perhaps the best to forgo. If you usually have little appetite in the morning, then missing breakfast is likely to be a better for you.

There’s no reason to be rigid with intermittent fasting either. If you tend to skip breakfast with ease but, say, find yourself uncharacteristically hungry one morning, then you may benefit from eating something that day.

On days where you’re intake of food is significantly reduced, it pays to emphasise foods that are highly nutritious and effective at sating the appetite. Protein and fat tend to pack most punch here, so appropriate foods might be fresh meat, oily fish, eggs and nuts, coupled with some green vegetables and salad for additional nutrients.

It’s important to remember that intermittent fasting does not need to be an endurance exercise. The aim is not to see how hungry one can get before caving in. This tactic usually backfires, because it will often drive people to eat frankly unhealthy foods. I advise gradual change, effectively training the body over time in a way that is practical, flexible and does not induce undue hunger.

Not for Everyone

Intermittent fasting has merit, I think, but it’s not for everyone. Those who should avoid intermittent fasting include individuals with a history of eating disorder and diabetics. Other individuals who are generally unsuitable candidates for intermittent fasting include those who are generally ‘stressed’ or have chronic fatigue. Stress can weaken organs known as the adrenal glands, and intermittent fasting can weaken these glands further, which may exacerbate symptoms such as fatigue. Individuals who are seeking to optimise their sporting performance should approach intermittent fasting with care, particularly if they are in an active phase of building muscle and strength. Working with a fitness professional with experience of intermittent fasting is advised. Those in any doubt about the appropriateness of intermittent fast for them should seek the advice of a doctor before making any changes.


1. Harvie MN, et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes (Lond) 2011;35(5):714-27

2.  Varady KA. Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss? Obesity Reviews2011 Jul;12(7):e593-60

24 Responses to My Times piece on intermittent fasting

  1. Paleo Suz 1 March 2012 at 4:16 pm #

    Very interesting reading. I’m currently reading a lot about (type 1) diabetes – in particular fasting, for the purpose of testing blood sugars to ensure insulin ratios are correct. I was therefore interested to read you don’t recommend IF for diabetics. Would you consider there to be any merit for a type 1 diabetic to do a complete “carb fast” instead for an extended period of time, rather than an IF?

  2. Jean 2 March 2012 at 11:46 am #

    Does intermittent fasting mean going without any nutrients at all for thst period or just missing the meal. I am thinking that I usually start the day with a coffee and cream and then breakfast. Would you advise taking the coffee black if I am skipping breakfast to try intermittent fasting?

  3. Mauro 2 March 2012 at 7:46 pm #

    I have been following a low carb lifestyle for over a year now, and supplement with 2/3 periods of intermittent fasting per month. I find that fasting from Sunday lunch to Monday lunch is quite easy to do (i.e have a normal Sunday lunch, and don’t eat again until lunchtime Monday, so you miss 2 meals and give your body 24 hours respite from food). If you’re already following low carb, it’s not much of step to do intermittent fasting successfully. When this has helped me particularly is getting past plateux.

    Not only does fasting help with fat loss, there’s a fair amount of evidence that it helps with cellular regeneration, as the body’s cells start to repair themselves when they have a break from food. And if you’re worried about the body going into “starvation mode” as a result of fasting, you needn’t worry – it takes 72 hours of fasting for this to happen, so it’s perfectly safe and healthy to fast for 24hours at a time.

  4. john doyle 2 March 2012 at 7:51 pm #

    What were your thoughts on this weeks Horizon programme on exercise?

  5. John Briffa 2 March 2012 at 7:57 pm #


    It was really good to see ‘high intensity intermittent exercise’ getting some mainstream attention, I thought. And loved the fact that it challenged the notion that exercise as is commonly advised for weight loss (aerobic exercise) doesn’t work very well for, err, weight loss.

  6. Helen Mould 2 March 2012 at 7:59 pm #

    I am 64 and have irritable bowel problems. In my 30’s I regularly started a diet with a fast as this, I felt helped me over food craving. Fasting I was later told encourages stretching and stenosis in the intestines as it interferes with the continuous movement of waste solids through the intestines causing prockets of waste to sit in some areas and none in others and was most likely a strong contributing factor in the development of ibs problems.

  7. Deb 2 March 2012 at 8:50 pm #

    I have the same question as Jean. I can very easily delay breakfast, but I drink my coffee with heavy cream. Does that break the fast and it would be best to drink my coffee black? I basically eat 2 meals a day, brunch and dinner, with a snack of protein and fat in between if I get hungry. Would it be better to mix things up and fast at different times so I am not in the same pattern every day?

  8. Scott 2 March 2012 at 9:26 pm #

    I have the same question as Jean and Deb. (In fact, out eating habits are so similar, we should open a restaurant!) I typically have coffee + heavy cream, brunch (a fry up, or yogurt, nuts and berries), and dinner (meat and two green veg, etc). Does this count as intermittent fasting?

  9. John Collins 2 March 2012 at 9:36 pm #

    Horizon. Yes, terrific on the exercise (I’d like them to do do HIT using weights next). Could you please explain two things about the English breakfast he had. 1) As well as the (now good!) saturated animal fats, he had beans, toast and what looked like mashed potatoes, all of which I understand are ‘sugar’ — is this correct, and if so would it have any bearing on the fat level in his blood sample? 2) Given that there is food fat in the blood, is this necessarily a bad thing — would it necessarily have a bad effect on the arteries, and also, what would happen to it if insulin is present (due to the beans, toast, spuds), and if insulin is not present? Many thanks and KUGW(Keep Up the Good Work); heard you on Woman’s Hour.

  10. Daisy 2 March 2012 at 10:53 pm #

    & I have (more or less) the same question as Mauro! I have been dabbling in IF for a while now, and lost 2 or 3 kilos (feeling like they’d been all located in the belly) fairly swiftly. I was thrilled with this solution, because with my madly busy lifestyle, it’s difficult to eat healthily when I’m out & about. However, they’ve all come back to roost since Xmas, on the same spot, and my IBS problems seem to be worse. Might Mauro have a point?

  11. Helen Howes 3 March 2012 at 12:10 am #

    Why not diabetics, please? I can understand that insulin users on old-fashioned regimes might be in trouble, but why not for others?

  12. Jean 3 March 2012 at 11:37 am #

    I, too, noticed that the fatty breakfast on the Horizon programme had a lot of carbohydrate in it. I thought the fat in the blood afterwards was probably normal and was then used by the body as fuel. Certainly not laid down as fatty deposits.

  13. Dr John Briffa 3 March 2012 at 1:48 pm #


    Not exactly intermittent fasting (and dairy products can be a bit ‘insulogenic’ but a lot better than cereal and/or toast!


    There’s the risk of hypoglycaemia (low blood sugar) if medication is not adjusted appropriately so I recommend working with a practitioner here.


    Yes, the breakfast was indeed carbohydrate-rich, and carbs can drive triglyceride (fat) production in the liver which can raise triglyceride levels in the bloodstream substantially and quickly.

  14. Jean 3 March 2012 at 7:38 pm #

    I knew that really! Black coffee it is, then, if I want to try I F

  15. Jennifer Eloff 3 March 2012 at 8:05 pm #

    FANTASTIC article, Dr. Briffa! Um, just for your info, as I know you like to help people, here is one lady with diabetes with a successful story. I’m not so sure it would work with all people with diabetes. I would think one would have to do it under the supervision of a knowledgeable doctor.

    Ok…I am officially a BIG, no HUGE IF fan. I have been on my weight loss journey for a little more than 6 months and have lost 65 lbs. so far. ( Lot’s more to go…)

    One of the big things that triggered my motivation was that I was so sick and I am a Diabetic. The Dr. wanted to put me on an insulin pump it was so bad!

    Well, since I have been losing weight, eating healthy and exercising my sugar has come way down but still high.I only needed oral meds.

    Since I started adding IF a week ago. for the first time in my life, EVER. My sugar is NORMAL!!! I don’t need any meds. It’s amazing the Dr.’s advice was really the opposite of what has worked!

    So, I must give full credit to this board for having the IF information!

    I really do think that this support forum helps save peoples lives. Especially when I personally experience things like this.

  16. Carol 6 March 2012 at 7:09 pm #

    I am type 2 diabetic and I don’t have any problem with a “breakfast” of coffee & coconut oil with cinnamon. I can (and do) often go three to five hours until a lunch of meat and vegetables. I have another small meal five to six hours later. Since I’ve been doing that, my fasting bs has been lower and I’ve felt better. It might be the coconut oil, so it’s hard to say for sure. I’ve been diabetic for almost twenty years and eating low carb for the past ten.

  17. Salim 7 March 2012 at 4:20 pm #

    Wouldnt it be better to skip dinner or have an early dinner, as this would allow for an emptier stomach during the night. Going by traditional mantras eating heavy in the morning and decreasing meal sizes throughout the day, helps in weight loss efforts. Personally skipping breakfast makes me more hungry during dinner and I tend to overeat.

  18. Mauro 7 March 2012 at 5:02 pm #

    I find having lunch at 12pm, then skipping dinner, breakfast and then eating again at 12pm, 24 hours later works best.

  19. Nick 28 March 2012 at 10:21 am #

    When I first made the shift to intermittent fasting, I did notice a decrease in energy as I was consuming less carbs on my non-WO days. After the shift, I’ve noticed a mental clarity upon waking up. Also, I don’t have such a foggy haze, almost like i was waking up from a hangover.

    There is a huge increase in the amounts of protein you eat, which can be more expensive.

    Either way, the pros far outweigh the cons!

  20. L. 10 April 2012 at 11:14 pm #

    Dr. B.,
    Do either of your books cover women’s issues – specifically – peri/men and or thyroid issues? Would IF be helpful?

  21. Jan P. Lopez 2 April 2014 at 12:59 pm #

    Whereas fasting can certainly aid the symptoms of Type II Diabetes specifically , a raw vegan diet & lifestyle have been shown to cure all symptoms and/or reliance on insulin from the disease.

    On the note of coffee & even coffee with cream (psuedo coffee) . As a lover of coffee who gave up having my usual black ( nothing added ) brew every morning , I would say the last thing you want to do whilst ‘ fasting ‘ is to consume even one cup , moreso with any cream !

    Cheers !


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