What is fasting?
You already know that what you eat is crucial for your health. But did you know that not eating, or intermittent fasting, is just as important? During fasting, your body can rest and repair, leading to benefits like accelerated fat loss and normalized blood sugar, cholesterol, and blood pressure. Plus, fasting saves you time and money.
So what does it mean?
How fasting (or reducing your eating window) works
When you eat, you often consume more food and energy than needed, storing the excess for later use.
Here’s how it works: After a meal, your body produces insulin in response to the carbohydrates, which turn into sugar. Insulin stores energy in the liver as glycogen. Once the liver is full, excess sugar is turned into fat and stored in fat deposits around the body.
Energy stored in the liver is limited but easily accessible, while fat storage is almost unlimited but harder to access.
Eating triggers insulin production and fat storage, while fasting lowers insulin, forcing the body to use stored energy and burn fat.
In essence, you’re either in a fed state (eating) or a fasting state. Balanced eating and fasting help maintain stable weight. Constant eating or snacking leads to weight gain as your body never uses stored energy.
To lose weight, you need to burn stored energy by fasting.
What are the benefits of a reduced eating window?
- More energy
- Improved concentration & feeling more alert
- Lower insulin and blood sugar levels (including reversing type 2 diabetes)
- Lowered cholesterol
- Reduction in inflammation
- Better stress management
- Better digestion
- Faster recovery after exercise
- Better immunity
- Lower risk of cancer
- Slower ageing
- Improved brain function & lower risk of dementia
Different types of fasting
When you eat, you often consume more food and energy than needed, storing the excess for later use.
Here’s how it works: After a meal, your body produces insulin in response to the carbohydrates, which turn into sugar. Insulin stores energy in the liver as glycogen. Once the liver is full, excess sugar is turned into fat and stored in fat deposits around the body.
Energy stored in the liver is limited but easily accessible, while fat storage is almost unlimited but harder to access.
Eating triggers insulin production and fat storage, while fasting lowers insulin, forcing the body to use stored energy and burn fat.
In essence, you’re either in a fed state (eating) or a fasting state. Balanced eating and fasting help maintain stable weight. Constant eating or snacking leads to weight gain as your body never uses stored energy.
To lose weight, you need to burn stored energy by fasting.
Shorter fasts
Time-restricted eating (TRE) is a popular fasting method recommended by nutrition practitioners. It involves limiting eating hours:
12-hour fast: Eat breakfast at 7 am and dinner at 7 pm, fasting for 12 hours. This follows the traditional three meals a day with no snacks.
14-hour fast: Extend fasting to 14 hours, eating between 9 am and 7 pm.
16-hour fast: Fast for 16 hours, eating between 11 am and 7 pm, known as the ‘lean gains method’. Adjust breakfast time or skip it based on the previous evening meal.
The 5:2 diet, popularized by Dr. Michael Mosley, involves eating normally for 5 days and restricting calories to 600 (men) and 500 (women) on two non-consecutive days. His “The Fast 800” book recommends 800 calories a day combined with Time restricted eating for metabolic benefits.
Longer fasts
Longer fasts, over 20 hours, are done less frequently than daily shorter fasts.
20-hour fast (The Warrior Diet): Eat one or two small meals between 3 pm-7 pm, once or twice a week.
24-hour fast: Eat dinner at 7 pm, fast until the next day’s dinner at 7 pm. Do this one or two days a week.
36-hour fast (Alternate Day Fasting): Eat at 7 pm on day 1, fast through day 2, eat breakfast at 7 am on day 3. This is occasional due to its difficulty.
Periodic fasting: Medical fasts of 5-7 days, done every few months under a nutritionist’s guidance.
The longest reported fast lasted nearly 400 days, with a man from Dundee, Scotland, consuming only water, tea, coffee, soda water, and vitamins. He lost 21 stone and maintained the weight loss with no health issues.
Women should fast differently
Most women need a slightly different approach to fasting compared to men due to their sex hormones and the ideal situation is you would work with a nutrition practitioner who can help you navigate the right path. On one hand, it doesn’t take much for a woman’s body to get destabilised. Studies show that, while fasting is often easy for men, women become stressed by fasting more easily (1). On the other, we’ve seen how fasting can help normalise blood sugar and insulin problems – so there’s a balance between giving your body a much-needed break from eating and placing too much strain on your body.
- Pre-menopausal women – fast until day 11 of cycle. No fasting while oestrogen peaks days 12-14, or day 14 onwards while the body makes progesterone.
- Perimenopausal women – fast days 1-11, no fasting 12-14, fasting again until day 28 (no fasting).
- Post-menopausal women – ideally no long fasts (13-15 hours is fine) as sex hormones are low.
Who Shouldnt fast?
Fasting may not work for everyone. If you are diabetic or very stressed, it is important to get your blood sugar levels on to an even keel first and TRE is not recommended. Start with a 12-hour fast on just two non-consecutive days per week to see how you get on. If you have thyroid issues, speak to your nutrition practitioner before trying fasting.
Also, some people with digestive symptoms may fare better on smaller, more frequent meals. They should seek professional guidance before attempting a fasting programme. It’s not appropriate for children, pregnant women or breastfeeding women, anyone very underweight (BMI less than 18) or those recovering from eating disorders.
Fasting may not work for everyone. If you are diabetic or very stressed, it is important to get your blood sugar levels on to an even keel first and TRE is not recommended. Start with a 12-hour fast on just two non-consecutive days per week to see how you get on. If you have thyroid issues, speak to your nutrition practitioner before trying fasting.
Also, some people with digestive symptoms may fare better on smaller, more frequent meals. They should seek professional guidance before attempting a fasting programme. It’s not appropriate for children, pregnant women or breastfeeding women, anyone very underweight (BMI less than 18) or those recovering from eating disorders.
Getting Started
The first job is to choose the kind of fast you are going to do and stick to it. If you know you’ve been eating a diet that’s not great, you’re a big snacker or you eat late at night, starting with a 12-hour fast is what you need at first. Do this every day for a week, eating three meals a day and no snacks.
As this starts to feel manageable (or if you are already pretty much eating to this kind of pattern), stretch your fast to 14 hours or 16 hours, again eating meals but no snacks in between. Whichever of these two options you choose, the ideal scenario is that you work alongside a health coach professional who can support you and guide you to choose the right foods during your ‘eating window’, and help you stay on track with your supporting habits and behaviours, so you can get the maximum health benefits.
They will also be able to tailor a programme to you so that it tackles any other health goals you have. Longer fasts are trickier to follow and should be carried out only when working with a nutrition professional. I warmly invite you to book a chat with me using the link below.
What you can consume when fasting
Water
You must stay hydrated and drink plenty of water. Drink a minimum of 2 litres. Don’t forget that the food you would normally be eating contains varying degrees of water or other fluids (like milk), and these will need to be replaced. You can flavour the water with lemon, ginger or cucumber, but avoid artificial flavours or sugar-free squash.
Tea
Any kind of tea is fine: black tea (regular tea), green tea or herbal teas.
Coffee
Drinking coffee is acceptable when you are fasting. Black coffee is ideal, although fasting expert Jason Fung also allows his clients to take a full-fat cream like double cream in their coffee. While not strictly a fast, he reports that the effect on insulin levels is so small, it is not worth worrying about.
Broth
Clear broths made from bones, meat or vegetables and flavourings like garlic, ginger or herbs. These aren’t soups – they should be entirely clear with no lumps.
My top tips when fasting
Keep busy
Keeping busy takes your mind off the fasting process and limits your internal questioning. Often people who are new to fasting will be looking for something to be wrong. ‘Will I start feeling hungry soon?’ and so on. Try to do all your usual activities exactly as you would if you were eating a normal meal. It can take your body a little time to adjust to your new fasting regime. You may feel a little weaker or lightheaded if you engage in strenuous exercise (like a high-intensity gym class). This is your body adjusting to burning fat for energy instead of sugar. If this happens, take things a little slower until your body learns to adjust. Keep in mind that many athletes train when they are in a fasted state.
Ride out the hunger
Until you become an experienced faster, there may be times when you feel hungry. Rest assured, your body has all it needs in terms of nutrition (your stored fat) to power you through the day. Hunger is just a feeling. Sometimes it can be a powerful one. The reality is that hunger is like a wave that may come and go. When you feel the hunger take hold, try deep breathing. There’s no magic to this, but taking some time to focus on slowly breathing in and out will help. Drinking a large glass of water or a mug of herbal tea when you feel a wave of hunger is also a good tactic.
Dealing with headaches
Some people may experience a headache when they first start eating this way. This may be due to a change in the electrolyte (salt) balance in your body. Ensure you drink plenty of water. You may also increase the amount of salt you eat around fasting – avoid table salt, however, which is highly processed, and choose a rock or sea salt, or Himalayan pink salt.
Dealing with constipation
Some people may also start to feel constipated and may not go to the toilet as much as they’re used to. Makes sense – less going in and, therefore, less to come out. If this happens to you, increase the amount of leafy green vegetables, and other non-starchy veg when you are eating to up the fibre content.
Break the fast gently
Don’t go from not eating to eating everything in sight. Your body needs some time to register that it’s full, so break the fast with a small but nutritious meal.
Check your prescription medications
There are some that you will need to take with a meal. These include aspirin, metformin and iron, and some blood pressure medications, too. You may find it is easy to switch to taking these during your eating window, but if in doubt, check with your GP.
If you feel unwell
If you feel unwell at any time, stop and ask for help.
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