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There are lots of diets that come and go in the media, but one that has been consistently hitting the headlines for several years now is intermittent fasting. Doctor and Personal Trainer, Frankie Jackson-Spence shares her thoughts on this new eating trend, and explores what the science has to say about intermittent fasting.
Take it away Frankie!
Intermittent fasting (IF) is an approach to nutrition that focuses on when you eat; restricting food consumption to certain window periods. Essentially meaning to focus is on when you're eating rather than watching what you eat.
The fasting period itself can be flexible, and common approaches taken are:
- The 5:2 diet: Probably the most famous fasting method. You can theoretically eat whatever you want 5 days a week, without having to count calories, and then reduce your calories to 500/600 2 days a week. The aim of this is to create an approximate deficit of 3500 calories per week, which aids weight loss.
- The 16:8 diet: This approach limits the eating window to only 8 hours a day, creating a 16 hour fast. For example, not eating your first meal until 12 pm and stopping eating by 8 pm.
So, what's the point? Well, it turns out there are a fair few proposed benefits to intermittent fasting.
Those who support intermittent fasting claim that this way of eating has multiple benefits. These include weight loss, a reduced risk of high blood pressure, type 2 diabetes and dementia and, most profoundly, an increased life expectancy.
The important question is whether or not intermittent fasting is only effective at causing weight loss by creating a calorie deficit, or whether the actual fasting period has any independent benefits. Multiple studies suggest that intermittent fasting is no superior in terms of weight loss, compared to a calorie controlled diet, as you still consume the same amount of calories, just within a smaller window of time.
Diabetes and heart disease
A good body of evidence suggests that some benefits of intermittent fasting go beyond weight loss. One study showed that a 16 hour per day fasting period increased insulin sensitivity and lowered blood pressure in people at risk of diabetes and heart disease, independent of how much weight they lost during the study period.
Eat less to live longer
The most exciting proposed benefit of fasting is the potential increase in life expectancy. Animal studies have shown that when your body is deprived of food, it metabolises its own cells for energy, starting with the least healthy cells and free radicals which are harmful molecules to the body. This has prompted the hypothesis that being in a calorie deficit increases the length of life. Sounds great! However, further evidence is needed to translate this into human studies.
This is all well and good, but there are also a few potential issues that come with intermittent fasting.
Like anything, there are always limitations to consider, and as a medical professional, it is important for me to make you aware of them.
- It is still under debate as to whether it is the metabolic effects of fasting that causes the health benefits, or the inevitable calorie deficit created as a by-product to eating for fewer hours in the day. Some people will struggle to restrict their eating window, and therefore is an unfavourable lifestyle choice without concrete benefits. Others will find focusing on food timings rather than counting calories much more favourable.
- Some studies have shown that the weight is regained if the IF diet is not continued. So this is something to bear in mind if you are just looking for some short-term weight loss.
- Fasting can cause unwanted side effects in some individuals including dizziness, nausea and feeling faint.
- There is some concern that intermittent fasting and advocating a restricted ‘eating window’ is promoting a restrictive relationship with food and unintentionally encouraging binge eating on the 5 days non-fasting.
- Many of the research trials are conducted on overweight individuals or animal studies. The supporting body of evidence on healthy weight individuals is not as extensively researched.
Overall, intermittent fasting is an exciting and promising prospect. It could be the answer to ending fad diets and focusing more on nutrient intake rather than calorie counting. On the other hand, it could be a big lifestyle restriction, particularly if the body of evidence is still under question and it does have its own potential side effects.
Intermittent fasting is a relatively new concept, and we need longer-term follow-up and more human studies to recommend it.
Please be aware that there are certain groups of people in which fasting is not recommended, including, but not limited to, pregnant women, children under 18 years, past medical history of eating disorders and type 1 diabetics. You should consult your own doctor and ideally, a registered dietician, if you are thinking about trialling the intermittent fasting regime.
I hope you feel more clued up about this spotlight topic!
Read what Dr Frankie Jackson-Spence has to say on L-Glutamine Vs Creatine.
You can follow Frankie on Instagram here @drfrankiejs
Would you give intermittent fasting a try? Or perhaps you use intermittent fasting as a way to lose weight and lead a healthier lifestyle?
We want to know your thoughts in the comments down below.