Fasting, part 3 - Sustainability

Fasting - From Now Until..?

I've done a fair bit of reading about fasting diets. Both from research literature, popular texts (there are a few in the bookshops at the moment!), and also online. 

Lots of people have things to say about fasting, and it tends to take one of two forms. Fasting is either the best thing since sliced bread - take that Atkins! Or it's yet another example of a terrible fad diet, with claims that it can cause anything from bad breath to disordered eating. 

But there's something that, in general, is missing from all of these commentaries. And that's the focus of this post. 

In my first post on the topic, I hope I gave you a reasoned explanation of what the diet is and how it works. But there is one more thing I'd like you to consider before embarking on this, or indeed any other 'diet'. 

My question is this - how sustainable is intermittent fasting/calorie restriction? Can you honestly say that it's something you can keep up for life? Or, in fact, do you need to?

If you undertake a fasting diet as a means of weight loss, what happens once you've lost the desired amount of weight?

At the moment, there is a distinct lack of evidence on how these diets work in the long-term. Particularly so with regard to human studies. So anything you read about long-term sustainability and maintenance of weight loss is likely to be based on speculation.

And sustainability and maintenance of your new weight are rather important.

As with all diets, there is a fundamental issue that rears its ugly head: here’s the scenario – it may well be familiar.

You follow the plan, you obey the rules and lose the weight. Congratulations! But now what? You can stop following the diet, right? Go back to eating ‘normal’ food, every day?

And watch the weight pile back on.

This problem is common to an awful lot of diets. People in general are quite good at losing weight, but not so accomplished at keeping it off. This isn’t an issue specific to fasting diets, indeed we’ve already recognised a lack of long-term studies. But there’s a fairly logical thought progression that says fasting diets, as with other diet plans, if discontinued, will cease to be effective.

So how can you maintain the lost weight?

At the risk of sounding rather dull - it comes back to the fundamental concept that you need to eat a healthy, balanced diet.

The Eatwell Plate

That’s not to say don’t follow a diet, by all means, try it if you will and if it’s safe for you to do so. But learn from it.

Fasting diets can teach you several things.

Firstly, hunger is a natural sensation – it lets us know when we are actually in need of food. There’s nothing wrong with feeling hungry now and again. Embrace it, and learn to listen to the cues from your body.  

Secondly – and perhaps most importantly – the fasting days might put portion sizes into perspective. Portion sizes, more often than not, are the culprit in weight gain. Eating anything in excess, including fruit and vegetables, can lead to weight gain. By fasting you may come to realise that you don’t need to eat quite as much as you think you do, or are accustomed to.

Thirdly, be mindful when you are eating. It’s very easy to pop things into your mouth without thinking about it, or eat whilst distracted. And mindless eating is a guaranteed way of exceeding your energy requirements, thus leading to weight gain. Fasting days demand attention to your diet if you are to stay within your strict calorie allowance. If you are able to apply that same mindfulness to your eating behaviour in general, you are more likely to remain in control of your diet and with it, your weight.

A Fast Way to Lose Weight?

Fasting

First things first, real fasting involves abstaining from all food and drink.

Various plans over the years, including detox diets, have advocated fasting, the more sensible of which allows for fluids.

These newly arisen fasting diets don’t advocate anything as extreme as avoiding all food and drink, but instead involve a significantly reduced calorie intake on ‘fasting’ days – usually a maximum of 600 kcal for men, and 500 kcal for women.

So this diet essentially advocates days of significant calorie restriction rather than actual fasting. But they use the term fasting, so I’ll stick with it for the sake of clarity.

The frequency of the fasting varies depending on what you read, but usually takes the form of either alternate day fasting (fasting every other day) or fasting on a 5:2 ratio - the latter involves fasting for two days per week. Both forms of the diet can be considered as intermittent fasting.

So what does it involve?

The pattern of the diet is variable – the frequency of the fast, as already said, varies depending on what plan you follow. Whichever it is it, the fast days involve restricting your calorie intake quite dramatically.

The general advice around calorie intake per day is 2000 kcal for a woman, and 2500 kcal for a man. Now, these are far too general to be of real use to the individual (but that’s another story), but do give us some indication of the rough energy intake that’s considered the norm/common. And it does give you some indication as to just how much of a calorie restriction you’re expected to follow on an intermittent fasting diet.

Let’s take a 500 kcal fast as an example. What do you get for your calories?

The answer, unsurprisingly, is not a lot. But it very much depends on how careful you are with your calories as to how much you have to eat.

For 500 kcal you could have a couple of slices of toast and peanut butter, and a Mars bar. And that’s it. Or you could have a couple of scrambled eggs for breakfast, a bowl of tomato soup and a salad at lunch, and a bowl of vegetable and lentil stew for dinner. This diet requires thought and preparation, and some knowledge and skill. And a liking for vegetables will certainly help.

  

How does it work?

Essentially, the diet involves days of calorie restriction. And when you restrict calories to a level below that which you use, you create a deficit which leads to weight loss. It’s fairly basic maths.

However – and there’s usually a however with diets – there are drawbacks.

There are various potential problems with fasting:

•  Hunger. As a society we’ve got used to being surrounded by food. For most of us there’s never any need or desire to allow ourselves to feel actual hunger. It’s not a pleasant sensation, but it is a natural one. It lets us know when we need to eat – not a drawback as such, but something to be aware of!
• Fasting can affect your mood – don’t be surprised if you find yourself feeling just a little bit grumpy on your fasting days.
• Low energy consumption can lead to low energy levels – on fast days, you may find you feel tired and struggle with normal activities.
• Following on from the above, if you exercise or are training for a sport you may well find your efforts feel that much more difficult than usual. By fasting you are essentially depriving your body of fuel, and the extra demands of being active may be one step too far for your dwindling energy levels.
• Fasting affects hunger hormones, causing a down-regulation of appetite. So after a few days of fasting you may find that you’re not bothered as much by feelings of hunger. However, on non-fasting days you may find that there is a rebound increase in the hunger hormones, stimulating a greater appetite than you would normally experience. This can lead to bingeing and overeating – and the excess calories eaten on non-fasting days can sabotage weight-loss.
• Fasting has an effect on your metabolic rate – low energy consumption causes a down-regulation in how much energy our bodies use, so whilst you may be eating less, your body is also using less. This down-regulation can linger even when you return to your normal diet, so it’s quite possible that you will gain weight on returning to a normal eating pattern.

However – yes, there’s another however – these diets are not well studied.

The known effects of fasting/very low calorie diets are usually applied to periods of extended fasting/calorie restriction. How these transfer to intermittent calorie restriction is not fully understood – and whilst that’s not necessarily something to deter you from following the diet, it is something to be wary of. The long-term consequences of this diet are simply not known.

Non-fasting days

There are different ideas about what and how you should eat on non-fasting days.

Should you eat ‘normally’, that is, stick to whatever dietary pattern you usually follow? Or can you splurge – reward your virtuosity for sticking to your calorie restriction, and devour anything and everything you desire?

Research into these diets advocates that you should maintain a healthy balanced diet on your non-fasting days. You need to get in the nutrients you’ve missed out on during the fast, and an excessively high calorie intake on your ‘feed’ days can sabotage any efforts on your ‘fast’ days. So whilst you may want to eat nothing but cream cakes and pies, try and stick to balanced meals and snacks. And remember there’s nothing wrong with cake and chocolate, in moderation.

Benefits?

In addition to the potential for weight loss, the fasting diets also seem to confer other benefits to general health.

In the few studies that have been published on these forms of dieting, improvements in various health markers were noted, including cholesterol and blood glucose.

Calorie restriction has been studied for years, with the focus being on its effect on longevity – and the findings suggest that there are benefits to be had. In addition to a reduction in levels of IGF-1 (insulin-like growth factor, a compound responsible for the ageing process), cholesterol and blood glucose are reduced, and with these so are your risks of cardiovascular disease and type 2 diabetes.

Anything else?

There’s always a last word to be had – is this eating pattern to be recommended? It’s hard to say. As a dietitian I like to work from evidence – high quality, rigorous evidence. And in the case of Alternate Day Fasting, 5:2 fasting, or any other configuration of calorie restrictive diets, the evidence just isn’t there yet.

The studies that have been published are promising, but there are some questions yet to be answered – what pattern of restriction works most effectively? How should you eat on non-fasting days? What level of calorie restriction is most effective?

Perhaps most importantly you need to consider how sustainable this eating pattern is. Do you just adhere to the plan for a finite period of time for the purposes of weight loss? What happens when you reach your goal? Do you revert back to your previous diet, which was probably responsible for your weight/cholesterol/etc. in the first place? Sustainability in diet and lifestyle is key to life-long health, and is intermittent fasting/severe calorie restriction sustainable?

It’s something to think about.

A word of warning – if you are diabetic, pregnant or breast-feeding, DO NOT follow this diet plan. It’s also strongly contraindicated if you have a history of eating disorders.

If you have any other health conditions, be safe and check with an expert before embarking on this (or indeed any other) diet.