A nutritionist’s review of intermittent fasting

Emma Brown - Nutritionist | 04 Jan, 2021

We understand that when it comes to losing weight, you have to find an approach that works for you. Whether this be tracking calories, eating fewer carbs, intermittent fasting or any other approach – here at Nutracheck we have you covered! Our app can be used to facilitate a wide range of dietary approaches, so you have complete flexibility to follow the one that's the best fit for your lifestyle. Throughout January I've been reviewing some popular weight loss approaches so you can decide which one may be right for you. Next up...

Intermittent fasting

How does it work?

There are a variety of intermittent fasting methods. Some involve implementing fasting periods where no food is consumed, whereas others focus on significantly decreasing total calorie intake. The most popular styles now are:

5:2 fasting diet – with this approach you eat normally on 5 days of the week. On the other 2 days you reduce your intake to between 500-800 calories, depending on which level you're following.

16:8 approach – this requires you to fast for 16 hours per day and to only eat during an 8 hour window.

OMAD (one meal a day) – this requires you to eat just one very large meal per day, within a 1 hour window. The aim would be to eat a sufficient amount of calories within this window and fast for the remaining 23 hours of the day.

Alternate day fasting – as it says on the tin, one day you can eat normally and throughout the next day you fast.

Essentially all of these approaches work to the same premise, you minimise your eating window or how many calories you consume on certain days, which naturally leads to fewer calories being consumed overall. This is ultimately why intermittent fasting approaches can be helpful for weight loss – because you're reducing your overall calorie intake.

Might it suit you?

These different fasting methods can essentially help you reduce your overall calorie intake, which is helpful if your goal is weight loss. Some people like the 5:2 approach because it only requires them to be super strict on two days of the week. The other five days, they can relax, as the very low intake on the two fasting days means they should naturally consume fewer calories over the course of the week.

As to the other approaches involving eating windows, some people might find these easier to stick to, as they only have to be strict at certain times of the day. In comparison to trying to reduce your calorie intake a little every day, requiring a level of daily self-control which some people find more challenging.

As with any weight loss approach, it's about finding what works best for you and your lifestyle. If intermittent fasting helps you stick to a reduced calorie intake across the course of a week and you find it manageable, then it's fine to do. It's just important to ensure your overall weekly intake is still at a heathy level to ensure you are getting all the nutrients you need to stay healthy. We recommend 1,400 calories as a minimum per day for most members aiming to lose weight – which equates to 9,800 calories across a week. Providing your weekly intake is reaching at least 9,800 calories, it doesn't matter so much when these calories are consumed.

Any downsides?

Feeling hungry – adjusting to extended periods of time without food can be difficult and does not suit everyone. It's likely initially you will experience some side effects such as feeling hungry, lightheaded and irritable. These side effects do tend to wear off over time as your body gets used to the change in routine, but not everyone is comfortable experiencing these.

Overdoing it when out of fast – it's important not to go overboard once you are out of a fasting period, as this could potentially undo your hard work while fasting. While there will be much more flexibility in terms of how much you can eat, you still need to stick within a suitable calorie intake to make the fasting day worthwhile.

Not a licence to eat anything – intermittent fasting is not a licence to eat lots of unhealthy foods in your non-fasting periods. It's still important to make healthy choices and follow the guidelines for a healthy balanced diet.

Not suitable for very active people – if you are someone who exercises daily, intermittent fasting may not work well for you. It can be more challenging to keep your energy levels up for exercise when having regular periods of fasting, so it's important to consider this before embarking on a fasting regime.

Reduced flexibility – having periods of time without food or very limited intake can make it hard to socialise or eat in the way we're used to. For example, the 16:8 approach may mean you eat between 8am and 4pm each day, allowing you to enjoy breakfast and lunch. However, it means missing your usual evening meal, which many people like to enjoy with their family.

What does Nutracheck track?

Nutracheck has a setting for the 5:2 approach so you can choose to follow this. To find this in the app, go to your diary and tap on the white chart icon in the top right corner. Scroll down and tap on '5:2 Diet'. You will then be able to select to follow 500 or 800 calories per day on your fasting days for women, or 600 or 800 calories per day on your fasting days for men. On the other days your calorie allowance will be set to match your maintenance calories – as the Fast Diet recommends eating normally on the other 5 days of the week.

In terms of the other fasting approaches, as these are really about timings you can still use the Nutracheck diary to track your intake when you are eating. You can use the Week View to ensure your weekly intake is still at a healthy level, even if you're having days where you fast completely. The Nutracheck online diary gives time stamps for food entry (sign in at www.nutracheck.co.uk)

Often people think intermittent fasting means they don't have to track their calories – and in some ways the different options approaches do naturally encourage a reduced consumption. But that said, continuing to track your intake when you do eat will help to ensure you're not eating too little across the course of a week or that you're not overdoing it when you're out of the fasting period.

Nutritionist's expert opinion

Intermittent fasting has become increasingly popular in recent years, thanks to it being a helpful way to lose weight for many. Aside from the weight loss benefits (which is simply due to the reduced calorie intake), intermittent fasting has also been shown to have potential health benefits.

There is evidence to suggest this way of eating can reduce blood pressure, increase insulin sensitivity thereby reducing the risk of type 2 diabetes, improve blood sugar control and potentially improve longevity – to name a few. Currently there haven't been enough studies in humans or long term research to ensure there are no long term detrimental effects. But as it stands the results looks promising.

If one of these approaches suits your lifestyle and you continue to consume a balanced diet and a healthy overall calorie intake, then absolutely give it a try. It could help with weight loss and potentially offer some other health benefits too.

Nutritionist Emma Brown (ANutr), MSc Human Nutrition is passionate about how food science applies to the human body, and how the nutrients in what we eat affect us and ultimately have an impact on our health.