Fasting for weight loss: guide, risks and benefits

What is fasting?

Fasting and intermittent fasting involve having periods of time when you refrain from eating, in different ways. Between fasts, the idea is that you eat as normal. Fasting therefore focuses mainly on when you eat rather than what you eat. There are different time windows and structured plans you can follow. Some of the most common methods are:

• 16:8 fasting – you fast for 16 hours and eat within an 8-hour window, with the fasting period often starting in the evening or morning.
• 14:10 fasting – a slightly gentler option where you start fasting at a set time and eat during a 10-hour window.
• 5:2 fasting – two days per week you follow a very low energy intake, around 500–600 calories, and eat as normal on the other five days.
• Eat Stop Eat – a 24-hour fast, once or twice per week, where the fasting period starts at a chosen time and lasts for 24 hours.
• Alternate-day fasting – fasting every other day, often with a very low energy intake on fasting days, usually around 500–600 kcal.

Which method you choose matters less than you might think. What they all have in common is that they can reduce overall energy intake in different ways. The most important thing is to choose the approach that works for you, your needs, and your everyday life.

How does fasting for weight loss work?

For intermittent fasting to support weight loss, it needs to be tailored to the individual – so that it feels sustainable and fits both your life situation and your health.

Intermittent fasting may support weight loss by:

• limiting the time you eat, which for many people leads to a spontaneous reduction in energy intake
• reducing total energy intake over the day or the week
• creating a clearer meal structure, which can make planning easier and reduce irregular eating
• leaving less room for snacking, especially in the evening or between meals

For some people, it can also work better to eat fewer but larger meals that feel satisfying, rather than many smaller meals that do not provide the same sense of fullness.

Benefits of fasting for weight loss

During fasting, the body’s way of using energy changes. As glucose stores decrease, the body begins to use fat to a greater extent as a fuel source. This can contribute to increased fat oxidation and – for some people – may also have positive effects on body composition and health.

It is important to remember, however, that increased fat oxidation does not automatically mean weight loss. Weight loss only occurs when total energy intake is lower than energy expenditure. The effects of fasting therefore vary between individuals and also depend on the fasting approach, lifestyle, and health status.

Possible benefits of fasting and intermittent fasting:

For some people, intermittent fasting can be a way to reduce calorie intake and therefore lose weight. Weight loss can in turn improve several aspects of metabolic health, such as blood sugar control and blood pressure.

There are also theories that fasting may have specific effects on cellular repair processes – known as autophagy – but this has not yet been demonstrated in studies in humans. Certain potential effects cannot be ruled out, but they are still not sufficiently explored.

In addition, any health effects of intermittent fasting may require following the method over a longer period, and some effects may only appear after more extensive fasting periods.

More research is needed to understand the long-term effects of intermittent fasting and which health benefits are relevant for humans.

Risks of fasting

Intermittent fasting is generally not harmful for people who are otherwise healthy and find that the method works for them. However, some groups should avoid fasting – such as people who are pregnant or breastfeeding, people with diabetes who are treated with insulin, and people who have, or have previously had, an eating disorder. For these groups, fasting can involve medical risks or add strain to an already vulnerable relationship with food.

Many people who try fasting experience tiredness, headaches, or reduced energy – especially at the beginning. For some, the method can also feel socially limiting, as meals often play a central role in everyday activities. Because many people tend to make healthier food choices earlier in the day than late in the evening, it may be more helpful for some people to keep breakfast and instead reduce evening eating when the goal is weight loss and more sustainable habits.

It is also important to be aware that a reduced energy intake – whether through fasting or other methods – can make it harder to get enough nutrients such as protein, fibre, healthy fats, vitamins, and minerals. Fluid intake can also be affected, as some of our daily fluid comes from the food we eat.

Do you have to eat breakfast, lunch and dinner?

Finding the right balance between eating and fasting is key to creating the conditions for sustainable weight loss. For some people, a regular meal pattern with breakfast, lunch, and dinner works best, as it can provide a steady energy supply and reduce the risk of snacking. Others experience better control of their energy intake by eating within a restricted time window or by fasting on certain days of the week.

Whether you are considering intermittent fasting or another method, the most important thing is to find a way of eating that is sustainable over time and works in your own everyday life.

When energy intake decreases, meal quality becomes even more important. It can therefore be helpful to choose foods that keep you full for longer, such as wholegrains, vegetables, pulses, and protein-rich foods. These foods contribute both to satiety and to making sure the body gets the nutrients it needs.

It is also wise to listen to your body’s signals – eating when you are genuinely hungry, and avoiding eating out of habit, stress, or routine. A mindful approach to meals can make it easier both to reduce energy intake and to build eating habits that are sustainable in the long term.

Long-term weight management

Sustainable weight loss is about more than short-term solutions – it requires long-term, realistic changes in lifestyle and behaviour. Research shows that small, gradual adjustments that can be maintained over time are far more effective than major changes that quickly become difficult to follow. Setting reasonable goals and noticing progress, even small wins, can help boost motivation and strengthen confidence in your ability to succeed.

Awareness of eating habits and strategies for managing stress, emotions, and everyday challenges without turning to food are also central to long-term weight management. It is about creating a balance that works in the long run and supports both physical health and wellbeing.

Long-term weight management is therefore not one single method or diet, but an interplay between behaviour change, regular routines, a nutritious diet, sleep, physical activity, and sometimes medical treatment. Over time, it is the small, consistent changes that make the biggest difference in reaching – and maintaining – a healthy weight.

Fasting as part of a comprehensive approach

Fasting can be one of several tools for someone who wants to lose weight, but it is rarely a solution in itself. Long-term weight loss requires a broader perspective where diet, physical activity, behaviour change, everyday movement, sleep, and – when needed – medical treatment work together.

At Yazen, we do not start from a specific diet or fasting model, but from what is sustainable for each individual. The goal is to help you develop habits that work in your everyday life and support both weight loss and long-term health.

Fasting can be combined with Yazen’s medical treatment when it is done in a safe and structured way, with consideration for medical circumstances and individual needs. In our work, the individual’s health, safety, and long-term sustainability are always at the centre.

Methods for losing weight

Many people look for strategies to improve their health and achieve sustainable weight loss. There are several different methods, and the most important thing is to find an approach that works for you and your lifestyle. Intermittent fasting is one example, where periods of eating are alternated with periods of fasting. For some, this can lead to reduced energy intake and provide time for recovery between meals, which may in turn have positive effects on health.

Beyond intermittent fasting, there are other well-studied strategies for weight loss. Increasing daily physical activity is one of the most important. Regular movement can not only increase energy expenditure, but also strengthen the cardiovascular system, muscle strength, and psychological wellbeing.

Whatever method you choose, it is crucial that it is sustainable over time and provides enough nutrition for the body to function optimally. There are many paths to weight loss, and often it is a combination of strategies that provides the best conditions for long-term results and improved health.

Summary

Fasting and intermittent fasting can, for some people, be a way to reduce energy intake and therefore lose weight – but the method is not universally effective or suitable for everyone. The effects vary depending on individual circumstances, lifestyle, and health, and fasting should always be part of a broader context in order to deliver sustainable results.

Research suggests that it is not the structure of eating that matters most, but whether the method leads to a long-term calorie deficit and is realistic to stick to over time. Potential benefits of fasting and intermittent fasting may include a clearer meal structure, less snacking, and in some cases improved control of energy intake. At the same time, there are risks – particularly for people with certain medical conditions, for those who are pregnant or breastfeeding, or for people with a history of eating disorders.

Ultimately, long-term weight management is about more than individual methods. It requires sustainable habits, balance in everyday life, a nutritious diet, adequate sleep, regular movement, and sometimes medical treatment. Fasting and intermittent fasting can be one of several tools, but are rarely the only solution on their own.

At Yazen, we take a comprehensive approach where the individual’s health, safety, and long-term sustainability are central. Our goal is to help you find the strategies and habits that work for you – whether that involves fasting, regular meals, or a combination of approaches – so that you can lose weight in a safe and sustainable way – and keep it off over time.