Fitness enthusiast Mack Brooks reviews the evidence available on the benefits of intermittent fasting, and whether you should try it.
Every few years, a new healthy eating or weight loss plan becomes popular. Recently, we’ve seen the explosion of keto, low carb, and the diet of the moment – intermittent fasting.
Intermittent fasting dictates restricted eating, with people following this way of eating by consuming food only during certain time frames. Some plans include specific fasting windows, for example, not eating for 16 hours within a 24-hour period. Others suggest eating every day, but heavily restricting the calories for a number of those days.
What is intermittent fasting?
While many of us are familiar with the idea of counting and restricting calories, not eating for large periods of time can be quite daunting. However, those that swear by intermittent fasting say that forcing your body into a fasting state for short periods works wonders, for weight loss and overall health.
A popular version of this kind of eating is the ‘5:2 diet’, which is five days of moderate normal eating and two days eating very few calories. The limits are usually less than 500 calories for women, and less than 600 for men.
Enthusiasm is growing for this diet, following research from studies on animals that suggest fasting can reduce the risk of certain cancers, diabetes and cardiovascular disease.
Does intermittent fasting work?
However, how or even if the intermittent fasting diet works is still under debate by scientists and researchers. Some experts believe that the possible benefits of intermittent fasting are simply down to overall restriction of calories. Others, that the periods of fasting lead to positive results. Either way, most of the evidence available is anecdotal.
So, should you try it or not? Here’s more information to help you decide. The most popular plans are the 5:2 diet (mentioned above), the 16:8 diet and fasting on alternate days (alternate day fasting – ADF).
- The 16:8 version involves only eating within an eight-hour window every day. This means fasting for 16 hours out of every 24. You choose which eight hours you eat within, no foods are banned, but you’re advised to eat normal portions.
- The 5:2 diet means eating normally for five days, and then reducing calories to between 500 and 600 on two days.
- ADF is where you fast every other day continuously. Some people eat under 500 calories on the fasting days or only drink water.
ADF is extremely restrictive and isn’t always recommended by doctors. It’s also difficult to stick to long-term, as it involves a lot of willpower.
Does intermittent fasting guarantee weight loss?
The short answer is no. While it will probably help you lose weight in the short-term, there’s no research showing long-term weight management with fasting. A review in 2017 of various research studies found that many (11 out of 17) showed significant weight loss, but the studies weren’t large enough or long enough to lead to conclusive results.
It’s likely that you’ll lose weight due to the overall calorie deficit, rather than the fasting itself. In other words, it doesn’t make any difference how you get to a calorie deficit, as long as you do.
While wellness bloggers and fitness gurus may make you feel like fasting is the answer to improving health and losing weight, scientific research is still in the early stages. There isn’t even a single definition for intermittent fasting, which makes it more difficult to ascertain long-term benefits.
Many experts do agree that occasional fasting can change how sensitive you are to insulin. This is one of the building blocks for metabolic health, weight management and prevention of diabetes. Many hormonal studies using intermittent fasting have only been carried out on animals, or on limited groups of healthy people, so results aren’t conclusive. A 2015 review of research found that intermittent fasting definitely has potential, but needs much more studying.
Is fasting for everyone?
The National Eating Disorder Association (NEDA) advises people with any history of disordered eating to avoid intermittent fasting, saying: “Many people report that their [eating]disorder began with deliberate efforts to diet or restrict the amount of food they were eating.” While intermittent fasting doesn’t restrict types of food, it could be seen as a form of restriction.
You can experience side effects too, such as feeling hungry or overeating in non-fasting periods or being tired or dehydrated.
Whether intermittent fasting is right for you is an individual choice. Most evidence of health benefits is restricted to anecdotal evidence for now. There is much to learn about intermittent fasting and its potential for weight loss, hormonal balance and any other health benefits. However, it definitely seems to suit some people who are seeking an eating plan that fits with their lifestyle.
My advice is to research it, talk to others doing it and consult with your doctor. If you have the ‘all clear’ from your medical expert, and understand how to ensure you eat the necessary nutrients during this eating plan, you could lose weight and feel better. Long-term… the jury is still out on that.
Mack Brooks is a fitness enthusiast who helps others realise their own fitness journeys and goals.