Intermittent Fasting

4th July, 2024

Whether it’s the 5:2 diet, 16:8 or simply skipping breakfast and not eating until lunch, intermittent fasting (IF) or time restricted eating (TRE) has taken the world by storm.

Dubbed by some as the miracle method for shedding unwanted pounds, but slated by others for being impractical and inconvenient, IF is a hotly debated topic.

Is it worth the hype? Or should we say no to intermittent fasting?

Let’s delve deeper…

So, what is Intermittent Fasting?

In a nutshell, IF involves avoiding food for a set period of time.  It could be 14 hours, 16 hours, or even an entire day! Most of us ‘fast’ throughout the night when we’re sleeping, so it may simply be a case of eating dinner a little earlier and breakfast a little later.  

During the ‘fasting’ window, no food is eaten, but water, tea and black coffee are all on the cards.

OK, so it doesn’t exactly scream ‘fun’. But what are there any benefits? 

A recent study randomized people to intermittent fasting or not intermittent fasting. However, researchers gave each group the same exact same meals with the same amount of calories, protein, fat and carbohydrates. Both groups lost the same amount of weight and the IF group did not show any improvements in insulin response compared to not fasting. So weight loss benefits are probably related to calorie restriction, rather than fasting. PMID: 38639542

What does the science say?

The purported benefits of IF are mostly related to weight loss, metabolic health and longevity.

  • Weight management

Several studies suggest IF could help with weight loss. One systematic review pooled together 40 different studies and found people doing IF had a weight reduction of around 7-11lbs over 10 weeks. But the researchers concluded this was really no better than just eating less calories overall. Essentially, with less time to eat, total food intake was lower.

  • Metabolic health

Another review found IF could improve blood sugar levels and lower insulin. For people with Type 2 diabetes, IF could help with weight management AND help with blood sugar levels. This was seen when participants ate within an eight-hour window every day (and fasted for the remaining 16 hours).

  • Lifespan

Research in animals shows that TRE might lead to longer lifespan. But there is a lack of data in humans.

Being a healthy weight is associated with living longer, but this also includes exercise, healthy food, plenty of sleep and limited stress!

What about IF for your gut health?

Research is limited, but there’s been some positive links between intermittent fasting and a healthy gut microbiome.

As you probably know by now, a thriving diverse microbiome (AKA the collection of microbes, including bacteria, that live within our gut) is linked to better overall health. From better digestion and bowel habits, to better mood and energy.

One study looked at people’s gut microbes after the holy month of Ramadan. People fasted for around 14 hours a day. They saw an increase in bacteria called Akkermansia, which is associated with better metabolic health.

How does it work? Well researchers reckon giving your gut time to ‘rest’ means it can focus on repairing and making your all-important gut lining stronger.

There’s got to be some downsides…?

IF isn’t for everyone. After all, it’s not always easy or convenient to skip food for such a lengthy period of time.

Here are just a few of the downsides you need to know.

  • The weight loss isn’t sustainable

As for weight loss, although research is positive, it’s not the holy grail. Most studies focus on the short-term benefits and don’t look at how (un)sustainable it could be. 

Researchers also often report that the reason IF might work initially is down to the overall lower energy intake – not because of what time you eat. So it’s no more effective than simply reducing the amount of food you eat.

And if in your ‘eating window’ you pack in triple the amount of food you normally would in a whole day… Well, you would put weight on.

Plus, IF focuses on HOW you eat, rather than WHAT you eat. If you’re eating lots of high sugar, high saturated fat foods, then you probably won’t see any benefits. It might be better to give your diet an overhaul instead.

  • Malnutrition

Having less opportunity to eat in the day means it might be trickier to hit your 5-a-day fruit and veg or 30-a-week plant food goals. And that means you could be risking nutrient deficiencies. It can be hard to get all the nutrients you need – like that all-important 30g of fibre – in just 1 or 2 meals a day.

  • IBS issues

If you’re tackling tummy troubles like IBS, or you’re often bloated, IF might not be a good idea. That’s because cramming all your food into a small window means your gut has to grapple with large loads all at once. A better option would be to spread your food intake across the day to lighten the load.

  • Fuelling exercise

If you get up early to exercise, you might feel famished by mid-morning and need some fuel to keep you going.

OK, so is it worth trying?

IF could have benefits for some people. If it’s weight loss you’re after, it’s definitely not a miracle method – so it depends what works best for you.

Short-term, if you want to give IF a go and see how you feel, go for it! You can actually get the gut health benefits from 12-14 hour fasts (e.g. 8pm to 8am), which is quite achievable. 

Just make sure you’re still eating lots of nutritious foods – think plenty of plants, colourful foods, lean protein, healthy fats and wholegrains. And be sure to stay hydrated during your fasting window.

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