What’s the deal with intermittent fasting
June 8, 2020
Intermittent Fasting has been a prevalent topic in the media for years now, particularly after the well renowned 5:2 diet was published. So what is “Intermittent fasting”?
What is intermittent fasting?
Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting (not consuming food). It does not say anything about which foods to eat, but rather when you should eat them.
There are three types of intermittent fasting;
1. Modified Fasting
Modi?ed fasting involves eating very little amounts of food on fasting days. Some modified fasts restrict intake on fasting days to 20 percent to 25 percent of needed calories. The 5:2 diet falls under this type pf fasting. Two days of the week are fasting and five of the days are non-fasting.
Energy requirements are individual, based on factors like height, age, gender, and activity level. But in general, a fasting day involves eating and drinking around 2,000 – 3,000 kilojoules worth of food and drinks. To put this in context, two boiled eggs, a slice of wholemeal toast, and an apple amount to around 1,000 kilojoules, so it’s clear to see a fasting day wouldn’t involve much food. On average an “eating” day will come to around 8,700 kilojoules, although the amount we need greatly varies between individuals.
2. Alternate Day Fasting
Alternate-day fasting refers to rotating days of eating and days of fasting. On fasting days no foods or beverages with calories are consumed. Calorie-free drinks, such as water, black coffee and tea are permitted. On non-fasting days, you can eat whatever you want.
3. Time restricted fasting
Time-restricted fasting limits the intake of calories primarily to waking hours. The goal is to fast 8 to 12 hours per day with the bulk of the fast occurring while you are sleeping. Extending the overnight fast to 16 hours has been stated as beneficial. Many of us do time restricted fasting without thinking about it. For example, if you eat dinner at 7:00pm and wake up and have breakfast at 7:00am that is 12 hours of fasting. This overnight fast is well known to reduce molecules in the body such as insulin and glucose that are connected to chronic disease.
What are the supposed benefits of intermittent fasting?
· Weight loss.
· Fasting can activate cellular mechanisms that help boost immune function and reduce inflammation associated with chronic disease.
· Improve risk factors for heart disease.
Breaking down the evidence
Intermittent fasting has been studied extensively in rats but only in small population group studies in humans, with long term evidence particularly lacking.
Studies have shown that intermittent fasting results in the same amount of short-term weight loss as any other kilojoule reducing diet. However, once someone has lost weight with intermittent fasting, they can gain back the weight more quickly once they start eating normally because during fasting the person’s body can go into starvation mode to conserve energy. If someone resets their metabolism during fasting, they can gain weight even if they eat very little.
It’s normal for people to develop strong cravings and feel out of control after fasting for a long period of time, so there is a danger of indulging in unhealthy dietary habits on non-fasting days. There’s likely going to be a strong biological push to overeat following fasting periods. Your appetite hormones and hunger centre in your brain go into overdrive when you are deprived of food.
With a reduction in body weight, there is also a reduced risk of heart disease (amongst other things) and therefore it is difficult to identify fasting, or the weight loss as the cause. In addition, there is a small amount of evidence to suggest that fasting decreases chronic inflammation that leads to metabolic conditions such as Type 2 Diabetes.
Intermittent fasting diets may lead to some unpleasant side effects, like fatigue, feeling foggy-headed, affected mood, feeling irritable, constipation, and headaches. Children and teenagers, athletes and highly-active people, those with diabetes, pregnant women, and people with eating disorders should all steer clear of fasting diets.
But what does it all mean for you?
We suggest to aim to maintain a suitable fasting period overnight of 8 to 12 hours. This might mean something as simple as pushing dinner forward and avoiding snacks before bed. A single fasting interval overnight is achievable and rarely interferes with someone’s lifestyle.
Intermittent fasting as a diet that constantly needs thought is something we would advise against because, as with any diet, it can be difficult to sustain and may cause feelings of failure if it doesn’t go according to plan, impact on being spontaneous with social occasions, but also produce unsustainable weight loss. If you were to choose this diet, consistent, smart food choices are necessary. Support from an accredited practicing dietitian would be beneficial to ensure your body is being nourished properly.
Making small tweaks to your current diet, like focusing on eating more fruit and vegetables, can lead to big changes in your health. Given that less than seven per cent of Australians currently meet the target of five serves of vegetables each day, there are clear improvements we can make to our everyday eating patterns – and for most Australians, this should be the focus.
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