To fast, or not to fast? An in-depth view into all things fasting!
Fasting for health or weight loss has been a hot topic for a number of years. If you are thinking of fasting or are looking for tips on eating well around fasting, read on to find out more.
There are various types of fasting, which is essentially a way to split the day or week into periods of eating and not eating. When you eat, we recommend focusing on nutritious and balanced choices.
Here are the main types of fasting:
- Intermittent fasting, usually with an 8-hour period of eating followed by a 16-hour fasting window, though these numbers may vary slightly. This is also known as time restricted eating.
- 5:2 diet, another form of intermittent fasting, is where 5 days of the week a person’s regular calorie intake is consumed, but 2 days of the week, around 500 calories are consumed. Again, this number can vary depending on the person’s needs.
- Longer fasting; periods of fasting where no food is consumed for full 24 hours, one or two days per week.
Although there are many other types of fasting, the above are the most common. But which type of fasting is the best?
Although there is no one size fits all approach, many people find the 16:8 fasting the most sustainable to keep up with, which is why it is often the most popular type of fasting seen.
Does fasting lead to weight loss?
It’s understandable to think that due to an extended period of not eating, weight loss will occur. This is because of the energy deficit that is created, resulting in weight loss.
Research has compared fasting as a method of weight loss compared to traditional diets, and most studies have found little to no difference in the overall weight lost.
So yes, it can result in weight loss, but it isn’t the only or best way to lose weight. It is important to remember that we want to focus on long term sustainable change, so finding a way to reduce calories that works for you is the most important – and that may or may not include some form of fasting.
What are other benefits of fasting?
There is some small but growing positive research in the field of fasting and how it can influence different health markers, such as:
Blood sugar management
Taking extended breaks from consuming food will lead to a reduction in blood sugar and insulin levels. Insulin is a hormone produced by the pancreas, that is needed to help our body use glucose (sugar) for energy. Although we want the body to have a good insulin response, if we have consistently high levels of insulin in the blood due to higher sugar intake or poor insulin control, this can increase risk of health issues such as type 2 diabetes. High insulin levels are also linked to more fat storage, therefore having lower levels of insulin output can reduce fat storage and improve weight management.
Improvement on insulin resistance
Insulin resistance happens when the cells do not respond as required to the insulin hormone, meaning glucose cannot be taken in by the cell to be used for energy. Because of this, the pancreas works harder to produce more insulin, but cells become more resistant to it. Fasting has been shown to improve insulin resistance, which can go onto providing better blood sugar control and reducing risk of type 2 diabetes.
Ongoing, chronic inflammation can increase risk of developing health issues such as rheumatoid arthritis and cardiovascular disease. If chronic inflammation can be reduced, this can also reduce inflammatory markers linked to these health issues. Intermittent fasts have been shown to significantly reduce levels of CRP (C-Reactive Protein), which is a common inflammatory marker.
Because fasting allows an extended period of time for the digestive system to rest without any food, this can help those affected by digestive disorders such as IBS or bloating. As the digestive system has time to rest and repair, rather than constantly working by digesting food.
There is a small amount of research that taking a break from eating for extended periods may help with cancer prevention, extending longevity and boost brain function, however the studies are mainly limited to animal research, and more human trials are needed before more solid advice can be given.
Whilst some of the benefits detailed above can be from not eating itself, they may also come from weight loss which is often seen when fasting. Another benefit is known as autophagy.
What is autophagy?
This is a cellular process that leads to the natural breakdown of damaged or unnecessary cells. This means the body can regulate the cells to promote newer, healthier cells, which is a process that can occur when fasting. This most likely happens only after 24h + of not eating. Again, most research has been carried out in animal studies, or has been short term in humans. Therefore long-term research in human trials need to be conducted.
Side effects of fasting
It is important to note that fasting will not be suitable for everyone to carry out safely, for a number of reasons.
Pregnant or breastfeeding woman should not undertake food restriction for a long period of time, as well as people who have a history of eating disorders or disordered eating, as it can be triggering for those who are vulnerable. Remember, eating disorders can develop at any gender, age and body type.
It is important to caution fasting practices if you take medications to manage diabetes. This is because it can interfere with how the medication works, possibly leading to health complications such as low blood sugar (hypoglycaemia), which can be life threatening.
Anyone with cancer and undergoing treatment should also not begin any fasting protocol without the advice from their cancer team.
The type of mindset followed when fasting is important. For example, if someone were to follow a fast with eating processed or high calorie foods, this can then take away from some of the benefits, such as the weight loss, and would be counterproductive.
There is also some evidence showing that calorie restriction can lead to an increase in the stress hormone cortisol. This can be true for those who already have high levels of stress in their lives, so fasting may not be appropriate for those. This is because higher than normal cortisol levels.
Women may not respond to fasting in the same way as men do, particularly at different parts of their cycle – read more here: https://dietitianfit.co.uk/fasting-and-the-menstrual-cycle/
Tips for fasting:
- Keep hydrated – Be sure to drink enough water throughout the day, minimum 2L daily. It is essential to drink plenty of water, especially when you are not getting any hydration from foods.
- Start slowly – Don’t go straight into 24 hour fasts! You may find it easiest to work on stopping after dinner snacking to help increase the window of fasting after dinner to breakfast.
- Plan meals – When breaking your fast, include a lean source of protein such as chicken, fish, eggs or tofu, as well as high fibre vegetables or salads, beans and lentils. Healthy fats such as avocado, nuts and seeds are important, and wholegrains such as brown rice and quinoa are great choices, for steady energy release.
- Prioritise protein – Protein intake is important at each meal, to ensure you maximise protein muscle synthesis and minimise any muscle wastage.
- Eat until comfortable – Be mindful of the portion sizes that are right for you. You want to prevent eating more than you need, to ensure you get the most benefits from fasting. When you feel satisfied (no longer hungry), then stop eating rather than stopping when you are feeling full.
- Avoid processed foods – Try to avoid highly processed foods or foods high in added salts and sugars.
- Keep stress under control- Work on stress management, as stress can be linked to having the urge to reach for food as comfort.
- Practice routine – Try to follow the same routine and timings to your fast, rather than sporadically changing meal timings or skipping meals. This will help with consistency, which is an important part of fasting.
- Think about exercise – If you plan to exercise whilst fasting, try to time it so that you are able to have a meal within the next hour after finishing exercise.
- Check with your doctor – if you have any concerns or existing medical conditions, we strongly recommend checking with your doctor before trying any form of fasting.