Nation of snackers: How intermittent fasting may boost our general health

Commenting on its 2019 report into consumer snacking in Ireland, Mintel research analyst Emma McGeown observed that it "continues to be, for many, a daily activity . . . " with "treat items such as chocolate and crisps . . . important to Irish consumers".

Of perhaps greater importance to Irish consumers is this statement from Diabetes Ireland: "Some 854,165 adults over 40 in the Republic of Ireland are at increased risk of developing (or have) Type 2 diabetes. More alarmingly, there are a further 304,382 in the 30-39-year age group that are overweight . . . (so) . . . 1,158,547 adults in Ireland need to consider making changes to their daily behaviours in terms of eating healthily and being more active."

Tara Kelly is a specialist obesity and diabetes dietitian and honorary clinical fellow at NUI Galway. She has helped pioneer a successful low-carbohydrate approach to healthy eating and diabetes management. She told The Irish Times that we have become a society of snackers: "Many of us eat from the minute we wake up to the time we go to bed. Even 30 years ago, that was unheard of. We are increasingly surrounded by targeted and aggressive marketing about eating and snacking which has normalised this way of consumption."

Mintel's Emma McGeown advises that "delivering on quality and indulgence will be imperative for sweet snacks' continued success", but a paper in the journal BMJ Evidence-Based Medicine states: "Two-thirds of people in the UK who have fallen seriously ill with Covid-19 were overweight or obese and 99 per cent of deaths in Italy have been in patients with pre-existing conditions, such as hypertension, diabetes and heart disease."

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And with an American study confirming Kelly's assertion that children and adults eat and drink more often during the day than they did in the 1980s, Does hunger and satiety drive eating anymore?, dare we halt "sweet snacks' continued success" and consider the benefits of intermittent fasting (IF)?

Although IF may seem to be a new dieting “fad”, Tara Kelly points out that it’s an ancient tradition across certain cultures and religions: “Fasting is a voluntary absence of food for a period of time, and patients are asking more about it.

Dietary intake

“What’s interesting about IF is that there’s no need to make huge dietary changes – no need to clear out the cupboards; and no need to spend hours in the kitchen. Fasting, for appropriate individuals, is a free and flexible method of managing dietary intake and for some, of improving their metabolic health.”

Kelly explains that while IF research was previously limited to animal investigations, more human studies have been undertaken – citing, for example, a 2019 review in the New England Journal of Medicine reporting that IF confers "broad-spectrum benefits for many health conditions, such as obesity, diabetes mellitus, cardiovascular disease, cancers and neurologic disorders" by eliciting an evolutionarily conserved, adaptive cellular response that "improves glucose regulation, increases stress resistance and suppresses inflammation. During fasting, cells activate pathways that enhance intrinsic defences against oxidative and metabolic stress and those that remove or repair damaged molecules."

And a recent report – Intermittent fasting, a possible priming tool for host defence against Sars-CoV-2 infection – even speculates that IF may help prevent Sars-CoV-2 infection by activating the immune response.

Drawing on her clinical experience, Kelly points out that fasting does not work for everyone, and no diet fits all: “I find that people who struggle with portion control or especially those with busy lives and jobs where they are usually eating on the go, actually find skipping a meal easier to manage than trying to choose healthier options. And although people can find a lot online about fasting, I always ask my patients to start slowly.”

Time-restricted eating

At a practical level, some of Kelly’s patients find it easy to start by eating in a 12-hour window only (for instance 8am-8pm). “However,” she adds, “I think this should be more of a ‘normal’ eating pattern rather than defined as fasting. Many people follow the 16:8 method. This is a type of IF known as time-restricted eating. It involves limiting one’s eating window to eight hours and ‘fasting’ for 16 hours – ie consuming no calories, although water and calorie-free drinks are allowed.”

Interestingly, Kelly highlights a 2018 five-week randomised controlled trial of time-restricted eating among pre-diabetic men which found that it enhanced their sensitivity to insulin and improved blood pressure and oxidative stress levels. It was the first randomised controlled trial "to show that IF has benefits independent of food intake and weight loss in humans."

Kelly explains that another popular type of fasting is the well-known 5:2 diet, where people restrict themselves to about 500 calories on two non-consecutive days per week: “This does not mean that people can ‘overdo it’ on other days. Any fasting method will help to reduce calories, and there is emerging evidence that some fasting patterns can improve our metabolic health, without the calorie restriction. One interesting study supported time-restricted eating earlier in the day over later in the day. However, I work with patients to see what works best for them.”

For readers considering an IF approach, Kelly emphasises the importance of people who are on blood pressure or diabetes medications not starting any fasting until they have conferred with a healthcare professional: “Fasting while on certain medications can be dangerous. Fasting regimens,” she adds, “are also not advised for any patient with a history of eating disorders or distorted eating.”

The Covid-19 pandemic has sharpened interest in the role of metabolic health. It appears that while IF is not necessarily a universal panacea, choosing not to contribute to “sweet snacks’ continued success” by ditching junk-food snacking is a useful first step.

Read: What I’ve learned from 12 weeks of intermittent fasting