Intermittent Fasting: The Facts
By Charlotte Foster BSc (Hons), MSc, RD
What is Intermittent Fasting?
Most diets focus on what to eat… but intermittent fasting is all about WHEN you eat!
With intermittent fasting, you only eat during a certain time period. This can be done in a number of different ways. The most common ways to do this is the 5/2 method where you calorie restrict on 2 days (usually 2 consecutive days) and then eat a balanced diet on the other remaining 5 days or the week, or the 16/8 method, whereby you fast for 16 hours and only eat during an 8-hour window throughout the day. Some people even go as far as a weekly 24 hour fast, but I would never recommend this! This basically means you will be eating dinner one night, and then not eating anything else until dinner the next day.
Many people argue that our bodies are practically made to survive and thrive by partaking in intermittent fasting, given that when humans were hunters and gatherers, our bodies evolved to go without food for many hours or even days. Whilst our bodies are indeed capable of doing this, now that we are no longer living in the prehistoric age – this isn’t exactly necessary!
However, it is true that a lot has changed since then! It is no longer so easy to maintain a healthy weight. 50 years ago, we didn’t spend our days working from home (30 seconds away from the fridge!), or spend our evenings sat down watching TV for hours. Being less active, as well as eating high calorie, fatty and sugary foods has made it more difficult to keep weight off.
Research has shown that intermittent fasting could be an effective way to combat extra calories and less activity – but I must stress that it is not the only way!
How Does it Work?
Whilst it is absolutely not unhealthy to eat 3 meals a day plus snacks, if you aren’t in a calorie deficit then you might be struggling to lose weight.
Even though there are lots of different ways that you can engage in intermittent fasting, they all work by the same principle. When you are consistently eating without enough activity, your body just burns the calories you have eaten. Therefore, intermittent fasting works because after going hours without food, your body will have already burnt through all of the calories from the last time you ate, so will start burning through your fat stores instead, in order to find energy.
What Are The Benefits?
Intermittent fasting has been proven to lead to weight loss. This could be to do with the fact that once your blood levels of insulin drop, it is easier for your body to burn fat. This could also be because you are eating within a smaller window throughout the day, so consuming less food in general (calorie deficit). Whilst there are many other bold health claims made, such as increased brain function, cancer prevention, reduced inflammation and cellular repair… there is little to no evidence suggesting that any of this is true. The only benefit that has been seen in clinical trials is weight-loss.
What Are The Negatives?
During trials, intermittent fasting has one of the highest dropout rates of all the different clinical diet trials. This is not surprising, because it really is so hard! Whilst it might sound easy to only eat within an 8-hour window, or just have 1 big meal per day, in reality this is much harder than you think. Symptoms that are commonly reported include headaches, faintness and nausea.
Is It Effective?
The reason intermittent fasting tends to work well for weight loss, is that by removing 1 or 2 meals per day, you actually put yourself into a calorie deficit.
It is so important to stress that intermittent fasting is NOT for everyone! Whilst it is proven to aid weight loss, the same weight loss can be achieved in easier ways. I absolutely would recommend sticking to your 3 meals a day and focusing on the nutritional content. If you are looking to lose weight, you should start engaging in label reading and opting for lower calorie options where possible. Instead of missing out meals, make sure you have a balanced diet full of wholegrains, fibre, lean proteins and healthy fats! In my opinion, this is the most sustainable way to lose weight.
If you are the type of person who can easily skip breakfast and just have a herbal tea, it might be right for you but if you are the type of person who feels faint and can’t concentrate after skipping breakfast… this is not the approach for you!
You should always consult a medical professional if you’re looking to engage in intermittent fasting, but if you have diabetes, a history of disordered eating, digestive problems or are pregnant/breastfeeding, I would stay well away from it.