It may often seem like there is always a 'new kid on the block' when it comes to weight management methods, and intermittent fasting is one that has been slowly increasing in popularity in recent years, in particular the catchy 5:2 method. For those who have tried and tested several weight management approaches, it may be difficult to navigate the truth, and to try and understand what works best for you. The FAQs below are based on the science (albeit limited science so far!), so you can get a better understanding of the benefits and limitations of intermittent fasting.

It's important to remember that people living with obesity are more likely to have micronutrient deficiencies, including an iron or vitamin D deficiency. Therefore, please speak to your healthcare professional before you start to restrict your diet, as they can perform the necessary assessments to support your health.

FAQs:

1. What is intermittent fasting, and how do you do it?

Intermittent fasting is a sweeping term that can be used when describing a program to restrict calorie-intake at certain times of the day, or week. This leads to periods of time known as extended fasting, where intake is typically around 25% of your energy needs.

One of the most popular and well known intermittent fasting methods is the 5:2 approach, where the extended fasting occurs on 2 non-consecutive days in the week. Another common approach is to follow 'time-restricted eating' where consumption is restricted to an 8-hour period within the day, and therefore the extended fast period is 16 hours daily. 

It is important to understand that many people around the world also fast for religious reasons, and this should not be confused with intermittent fasting. For example, during the holy month of Ramadan, many complete a 12 hour fast each day, from sun rise to sunset. 

2. How does intermittent fasting compare to popular diets?

It is important to remember that the scientific research for intermittent fasting is still evolving. Most recently, researchers who studied around 600 participants with overweight or obesity, have found that when following an intermittent fasting approach, people lost on average between 4-8% of their body weight over a six-month period. When compared to other diets that require a continuous restriction on energy intake, similar levels of weight loss were achieved.

When comparing weight management approaches, it is important to not just look at how much weight is possible to lose. The popular and well researched Mediterranean diet, where food intake can be characterised by a high level of plant-oriented food, and low levels of processed food, generally sees a similar level of weight loss, but has greater impact on your body's cardiovascular system. A recent Spanish study found that an energy-unrestricted Mediterranean diet can reduce the risk of a major cardiovascular event by up to 30%. This study focussed specifically on people who lived in Mediterranean countries with an already high cardiovascular risk, so it's important to understand your own body when comparing weight management approaches. You can find out more about the benefits of weight loss to your cardiovascular system here.

It is important to remember that when it comes to weight loss, changes to your diet are just one part of long-term management. Your healthcare professional will be able to recommend a weight management plan that is best for your lifestyle, as there is no 'one size fits all' method when it comes to managing your weight. 

3. How does intermittent fasting affect your BMI?

Your Body Mass Index, often referred to as BMI, is a measurement of height compared with weight. It is the most common way to assess for overweight and obesity. For example, a BMI of 25 kg/m2 or ≥ 30 kg/m2, indicates overweight and obesity respectively. 

For some people, intermittent fasting can lead to a reduction in BMI, although despite its widespread use in the medical community, BMI alone as an indicator for obesity has limitations that you should be aware of when using the indicator as a measurement of health.

4. Should you restrict your food intake if you are prescribed a weight management medication?

When talking to your healthcare professional about weight, they may prescribe you a weight management medication. There are several types of weight management medication, and they work with the chemistry in your brain that causes weight gain and prevents weight loss. Weight management medications are prescribed by healthcare professionals as a long-term approach to weight loss and can limit weight regain if continuously used.

Medications should always be taken alongside changes in nutrition and physical activity, rather than as an alternative.

As previously mentioned, for some, fasting is a religious practice rather than a tool for weight management. Studies into whether weight management medication is still effective during periods of fasting have so far shown that there is no change in how they work. However, some weight management medications can impact a person's iron, vitamin D and other nutrient levels, so it is really important to consult your healthcare professional before you embark on periods of fasting when prescribed a weight management medication. 

5. Do the outcomes of intermittent fasting differ between males and females?

As a common theme, the research into biological sex differences for intermittent fasting is limited, however there is no significant difference in how women respond to intermittent fasting versus men.

6. Should intermittent fasting be seen as a long-term approach to  weight  management?

It is important for your professional to tailor a nutrition plan that meets your personal preferences, and treatment goals. This can take in a variety of factors that ensure safety, nutritionally sufficient, affordable and suitable changes for your lifestyle. For some, intermittent fasting may be appropriate, but there is limited evidence to show it can lead to weight reduction in the long-term.

Continuous calorie restriction may increase the chances of weight gain in the long-run, as this type of restriction can change the way your body signals hunger, satiety and body weight regulation. 

In cases where behavioural interventions (diet and exercise) don't work to manage your weight, psychological therapy, pharmacological therapy, or bariatric surgery can help you lose weight and prevent weight regain. For long-term weight management strategies, it is best to speak to your healthcare professional, who can assess your lifestyle to work out the best approach for you.