How to do intermittent fasting (IF)

by Dr Deborah Lee, Dr Fox Online Pharmacy

You will no doubt have heard about IF, sometimes called time-restricted eating (TRE). This is a popular option for anyone wanting to lose weight. Around 10% of the population are currently doing IF. The term IF is one of the most popular searches on Google.

• But what is it? How does it help you lose weight? How do you do it?

Read on and find out.

What is IF?

IF means eating only during a set time period during the day. For example, the 16:8 diet means that you only eat during an 8-hour window. The other 16 hours, you are fasting. This is important as by not eating during these 16 hours, your body has used up all available glucose for energy and is forced to break down fat (ketones) instead.

There are several types of intermittent fasting –

• 16:8 – The easiest way to do this is to eat between 12 pm and 8 pm. This means that for most of the 16-hour fast, you will be asleep, and it only means skipping breakfast.
• 14:10– Some people find it easier to eat between 9 am and 7pm, which gives them a 14-hour overnight fast.
• 5:2 – This means fasting for 2 days a week and eating normally for the other 5 days. Fasting can be on any day of the week, but these should not be consecutive days.
• Alternate day fasting – This means fasting every other day but eating normally on the day in between.

How does it work?

Research shows that time-restricted eating naturally results in people eating between 250-550 fewer calories per day. Plus, fasting for 1- hours, ’flips the metabolic switch’, meaning you start to burn fat to release energy.

In one review of 40 studies, following IF for 10 weeks results in weight loss of between 7 and 11 pounds.

What to eat during the eating period?

On a non-fasting day, you eat normally, such as 1800 to 2000 calories per day. You should not really be counting calories, but eating a healthy, balanced diet with plenty of lean protein, fibre, fruit, and vegetables. It stands to reason that if you overindulge on chocolate, cookies, and ice cream, you won’t be losing weight! Keep high-fat, high-sugar foods to a minimum.

What to eat on a fasting day?

On a fasting day, you eat only 500-600 calories. The same applies as above, in terms of what you should eat. There are plenty of websites and recipes with ideas about what to eat on a fasting day, for example BBC Good Food

You must drink at least 2 Litres of fluids per day, but this should be water, black coffee or tea, or herbal tea, and no sugar or sugary drinks.

Note that when fasting, absolutely no calories should be consumed. Even one biscuit or one spoonful of sugar in your tea, will break the fast and stop the weight loss. You must fast completely.

Any side effects?

Initially, some people complain of feeling hungry, tired, having headaches, being light-headed or dizzy, feeling sick, mood changes, and insomnia. But, as time passes, these generally settle, and most people say they feel really well on the regimes. Hunger tends to fade, and you will get better at saying ‘No’ to food during the fasting periods.

Medical benefits of IF

IF has been shown to improve insulin sensitivity (the way your body processes sugar). This means it can help reverse pre-diabetes. It also lowers the level of chronic inflammation in the body, which has numerous health benefits. It stimulates autophagy – the recognition and destruction of abnormal and dead cells. This is important as unchecked, these cells can lead to the development of cancer. Some studies show that people on chemotherapy for cancer do better when they couple the regimen with IF.

Weight loss lowers blood pressure and reduces the risk of heart disease, as in a heart attack or a stroke. Some research suggests that IF may benefit brain health and might reduce the risk of Alzheimer’s and Parkinson’s Disease.

Who is not suitable?

IF is not suitable for

• Children
• Women trying to conceive, pregnant or breastfeeding
• Anyone with diabetes as they need to eat regularly
• Anyone with a history of an eating disorder
• Those on medication that needs to be taken regularly with food
• If you have a chronic medical condition or take regular medication, always check with your GP before you start IF.

Pitfalls of IF

Choose a regime that is most likely to fit into your lifestyle. Be prepared for side effects, but take heart as these do gradually disappear. Think of a strategy to deal with hunger when it strikes. Ideally, find something to distract you, such as going for a walk, doing a hobby you enjoy, and keeping busy, for example, doing the housework. Drink more water. Be patient, because like any weight-loss diet, IF is not a quick fix, but you should start to notice weight loss after 4 weeks. IF is safe and has been studied in those following it for up to 1 year.

Final thoughts

IF is a great way to tweak your diet and lose weight. It doesn’t mean having to buy expensive food and copy complicated recipes. It relies on you eating a healthy, balanced diet, but by watching the clock and not focusing too much on calories. Doing this will result in weight loss. Many nutritionists are hugely in favour of IF, for example, the health specialist Dr Michael Mosley

• Could IF help you  lose weight?
• What could you do today to get started?