Intermittent Fasting (often referred to as ‘IF’) has become increasingly popular in recent years. You may well have tried it yourself or may know someone who has. But is IF just the latest ‘here-today-gone-tomorrow’ fad diet, or does it offer us a safe-and-effective approach to achieving long-term, healthy weight? Corporate nutritionist Angela Steel, Founder of SuperWellness, shares her views.

If Intermittent Fasting is something you are currently considering, here to help you decide whether or not to try it are a few questions I believe you ought to be asking yourself first, and also a round-up of the available research so far.

Different fasting approaches

Intermittent fasting (IF) means that you restrict your eating during certain times, either completely or to a very low-calorie allowance. The rest of the time, you eat normally. The most common approaches include:

Alternate-day fasting: alternating between ‘normal eating’ days and days when you only have one meal that provides about 25 per cent of your daily calorie needs.

Whole-day fasting: 1 or 2 days per week of complete fasting or restricting yourself to up to 25 per cent of your daily calorie needs, and normal eating on the other days. The 5:2 diet is a popular example of this. On this plan, food on fasting days is restricted to 500 calories for women and 600 calories for men.

Time-restricted eating: restricting food intake to a particular window during the day. The 16/8 approach involves eating only during an 8-hour window and fasting during the remaining 16 hours. A more flexible approach is to leave a minimum 12-hour window without food each day. So, if you finish eating your evening meal at, say, 8pm, you aren’t allowed to eat your breakfast until at least 8am.

Why consider Intermittent Fasting?

Although intermittent fasting is mostly recommended for weight loss, it has been associated with many other health benefits as well. Studies have shown promising results for improving blood-sugar levels and cholesterol, boosting longevity as well as protecting the brain against Alzheimer’s.

Aside from obviously decreasing your calorie intake, it may also have a deeper physiological effect. Some people believe it triggers an immune response that repairs cells and improves your metabolism.

It’s likely that IF works on a hormonal level, too – reducing levels of insulin, a hormone that promotes fat storage, and increasing human growth hormones, known to improve body composition and metabolism.

Does Intermittent Fasting work?

A systematic review of 40 research studies found that IF does work for weight loss, typically resulting in 7-11 pounds shed over 10 weeks. And if you’re worried that IF will make you want to eat more on non-fasting days, studies indicate this isn’t generally the case.

The million-dollar question: is IF more effective than other approaches? Studies that compare it to ongoing calorie restriction haven’t shown conclusive results on this. The research showed that it isn’t necessarily easier to follow than other diets either.

How would Intermittent Fasting fit around your training?

It’s a good idea to take your training routine into consideration when planning your IF timetable. Some research has found that working out first thing on an empty stomach may have some fat-burning benefits, but there is a concern it may also cause us to break down muscle.

With glycogen stores depleted, your body could end up using protein from the muscles for fuel. You might find it makes you feel a bit queasy or that you have less energy to power a good workout.

It’s worth experimenting and seeing how it feels for you. If you experience any adverse effect, then I’d advise that you plan your more intense workouts away from fasting times.

Ask yourself: ‘Is Intermittent Fasting right for you?’

The science tells us that intermittent fasting works. Unlike crash diets, which lead to short-term weight loss, it also seems to work its magic on our metabolism and health.

There are circumstances under which you should not try Intermittent Fasting, for example if you suffer from diabetes, have certain eating disorders, are taking medications that require food, are a child or adolescent in an active growth stage, and if you are pregnant or breastfeeding.

If you have any doubts about whether your personal circumstances are appropriate for you to begin an Intermittent Fasting programme, then you should take no action before consulting your GP.

And if you are someone whose stomach cries out for a hearty breakfast as soon as you wake up (as mine does), you may want to look at other approaches.

Intermittent fasting may not be for everyone, it may not be a panacea, but it’s certainly an option worth considering.

More information

Angela Steel

Corporate nutritionist Angela Steel


Angela is the Founder of SuperWellness, one of the UK’s leading corporate nutrition consultants. Now in their 10th year, they have supported over 100 businesses using bespoke programmes and challenges to improve their teams’ physical and mental health and fitness at work and at home. Email [email protected] or call 0845 370 4070.

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