Positioned as the weight loss solution for foodies, intermittent fasting – whether it falls under the 5:2 or 16/8 umbrella – allows you to eat normally alongside periods of a restricted calorie intake. But is a diet where you can eat what you want most of the time too good to be true? And are there any hidden risks? We found out…
What defines intermittent fasting?
Intermittent fasting – often referred to as IF – is not actually a diet, it’s an eating pattern. You incorporate regular periods of fasting into your meal schedule, whether it’s eating normally for five days and limiting calories for the remaining two or eating within an eight-hour window every day. Due to its reported health benefits, fasting has been a buzzword in the wellness world since the 5:2 gained momentum in 2013.
What exactly are the benefits?
Studies have investigated fasting for decades (fasting itself has been used for thousands of years for various purposes), and a number of them suggest people who fast have better memories, more energy and improved brain function. Other studies show fasting can boost heart health, reduce the risk of disease and extend life span. One of the biggest research-backed benefits is weight loss, with additional findings suggesting intermittent fasting causes less muscle loss than other forms of continuous calorie restriction.
Are there any other advantages?
- Boost your metabolism: Fasting changes your hormone levels, increasing the release of fat-burning hormones and normalising levels of ghrelin (the hunger hormone). It also decreases insulin levels and can boost metabolism by up to 14% – essentially fasting makes your body work more efficiently, making stored body fat more accessible.
- Lower the risk of type 2 diabetes: Fasting has been shown to make the body more sensitive to insulin, and the more sensitive your body is to insulin, the more efficiently it uses the food you consume. Anything that reduces insulin resistance can also help to lower blood sugar levels and protect against type 2 diabetes.
- Fight cancer: Fasting is believed to reduce the levels of IGF-1 in the blood – a growth hormone which seems to lead to accelerated ageing and can cause cell divisions like those found in cancer.
- Give yourself flexibilty: With no complicated rules, fasting is a simple and flexible way to lose weight and boost health. It also means you’ll save money and advocates claim to feel empowered by fasting as it removes the stress of calorie counting and the dilemma of deciding what food to eat.
- Safety: Research shows intermittent fasting is safe. More than that, experts say it’s actually what our bodies were designed for. Our hunter-gatherer ancestors didn’t have the steady access to food we do now – our bodies evolved to be able to function without food for extended periods of time.
Are there any downsides?
- A need for self-control: Fasting for several hours doesn’t give you permission to eat whatever you want in whatever quantities you want, however hungry you may be. When you finish your fast, you need to pretend the fast never happened – no compensation, no reward or special way of eating, which can require a lot of self-control. However, research has suggested that by re-training your hunger hormones, it’s likely a smaller amount of food will fill you up and you’ll lose the urge to binge with time.
- Not for everyone: If you’ve ever had an eating disorder, steer clear of fasting, as it could trigger a return to unhealthy restriction. At the same time, it should be avoided by those with a thyroid or adrenal issue (fasting can cause a state of stress on the body, which can send already high cortisol levels into overdrive) and keen gym bunnies may struggle with a lack of energy during their workouts.
- Not a quick fix: If dropping pounds is your goal, be patient, as weight loss from a fasting diet is slow (often only 0.5lb per week) but consistent. This, in turn, requires dedication on your part – those that have the most success with fasting for weight loss adopt it as a long-term approach to losing and maintaining weight, not a quick fix to drop weight fast.
- There’s more to a diet than calories: 500 calories from an avocado will digest and affect your body quite differently from 500 calories of crisps – limiting calorie intake can reduce nutrition intake, meaning you may not feel as energised. Many nutritionists say looking at calories alone is too reductionist and overly simplified.
Could eating less provide the same benefits?
Yes and no. For some people, simply eating less and being more aware of portion size is a more sustainable form of consistent weight loss, while fasting works better for others. However, science suggests fasting may be a better bet. In short, your body has two states, the fed state and the fasted state. The fed state starts as soon as you begin eating and lasts for three to five hours. In this state, it’s tricky for your body to burn fat as insulin levels are high. After that, there’s a period of eight to 12 hours (when you sleep) when your body isn’t processing any food. Around that 12-hour mark, you enter the fasted state, when your body begins to burn fat. When you’re consistently eating (i.e. not fasting), science therefore suggests you may struggle to lose weight, even if you are on a calorie restricted plan.
If fasting isn’t for you but you’re still looking to reap some of the benefits, some nutritionists suggest leaving a clear 12-hour window between supper and breakfast – if you have your evening meal at 8pm and don’t have breakfast till you get to the office at 9am, you’re already doing this.
The bottom line?
There’s no doubt fasting for weight loss works, but so do a lot of other approaches. Some research suggests a very low carb diet yields the same benefits as fasting, without requiring you to stop eating. If you find yourself overeating after a fast or if you get shaky and light-headed while fasting (signs of hypoglycaemia), fasting probably isn’t the best approach for you. But if you have a healthy relationship with food, are looking to lose more than half a stone and are willing to see it through in the long-run, it could be worth giving it a go.