Globally, in the 21st century, the obesity pandemic has become a large-scale issue with Public Health England estimating that two-thirds of adults in the UK are overweight, and this figure is expected to rise to 70% by 2034. It results in a huge burden on the healthcare system, costing approximately £6 billion to the NHS in 2014, which was more than the amount spent on the police, fire service and judicial system combined, and with declining rates in physical activity due to the likes of technology overuse this figure is only going to increase. Obesity is a risk factor for a multitude of chronic conditions ranging from type 2 diabetes to coronary heart disease to cancer so it has become a major focus of public health efforts to reduce it.
Dieting is an inexpensive and non-medicinal way to combat obesity, with 40% of women and 20% of men dieting at any given time, and out of the dietary interventions, the daily calorie-restricted appears to be the most used. Its success, however, is varied and rarely results in sustained weight loss as individuals struggle to adhere with it and give-up very quickly so all improvements made are lost. Therefore, in the last decade, intermittent fasting has been gaining more publicity globally in scientific literature and was popularised by Dr Michael Mosley in his ‘Eat, Fast and Live Longer’ documentary aired in 2012 on BBC and later in his book published in 2013, ‘The FastDiet’.
This entails a different approach and commonly consists of fasting for 2 non-consecutive days per week where between 0-25% of the normal calorific intake is consumed; approximately 600 calories for males and 500 calories for females. During non-fasting days, consumption is usually ad libitum- no specific restrictions are in place, and this is its major advantage compared to other approaches where the individual has to constantly diet. A reduction of body-weight by even 5% can result in an improvement in the quality of life and reduce the risk of morbidity and mortality. I became interested in intermittent fasting after reading an article by Conley et al.1 in Nutrition & Dietetics, 2018.
They instructed 23 male obese participants to follow the 5:2 diet and monitored them for a period of 6 months. Intermittent fasting decreased BMI, weight, waist circumference and improved mental well-being. The mean weight loss was 5.3kg (5.5%) across the group which was in line with Varady et al.2 who demonstrated a significant 5.2kg weight loss over 12 weeks with the same diet. Waist circumference, visceral fat, saw a huge drop, with the group losing an average of 8cm off their waistline which reaps many health benefits as it is a major risk factor for type 2 diabetes and heart disease. There were no significant differences recorded in fasting blood glucose or lipids however Klempel et al.3 found that after 8-12 weeks there is an approximate 25% decrease in low-density lipoproteins which can increase the probability of atheroma formation and consequently myocardial infarction. Quality of life was not impacted negatively and psycho-social dimension scores increased and in another study by Harvie et al.4 32% fewer people reported depression and improved mood.
No adverse side effects were recorded- hunger was experienced by over half during the initial 2 weeks but then only 18.2% after 6 months and Kroeger et al.5 also found similar findings. In 27 other trials, binge eating and mood-related side effects were reported but these were no different from the baseline.
17 of the original 23 were able to adhere with the diet so adherence rates were high and consumption of all macronutrients was reduced so nutritionally it was appropriate however there was a lack of fibre in the diet. Intriguingly individuals did not overeat after fast-days to compensate for the calorie deficit generated and it did not promote the consumption of unhealthy food choices which are high in fat, sugar or salt.
In conclusion, research shows that intermittent fasting is a promising and feasible weight loss strategy- it is balanced nutritionally and actually works. However, not all studies support this view and further long-term studies are needed to confirm its effects.
 Conley M, Le FL, Haywood C, Proietto J. Is two days of intermittent energy restriction per week a feasible weight loss approach in obese males? A randomised pilot study. Nutr Diet 2018; 75(1):65-72.
 Varady KA, Bhutani S, Klempel MC, Kroeger CM, Trepanowski JF, Haus JM et al. Alternate day fasting for weight loss in normal weight and overweight subjects: a randomized controlled trial. Nutr J 2013; 12(1):146.
 Klempel MC, Kroeger CM, Varady KA. Alternate day fasting (ADF) with a high-fat diet produces similar weight loss and cardio-protection as ADF with a low-fat diet. Metabolism 2013; 62(1):137-143.
 Harvie MN, Pegington M, Mattson MP, Frystyk J, Dillon B, Evans G et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes (Lond) 2011; 35(5):714-727.
 Kroeger CM, Trepanowski JF, Klempel MC, Barnosky A, Bhutani S, Gabel K et al. Eating behavior traits of successful weight losers during 12 months of alternate-day fasting: An exploratory analysis of a randomized controlled trial. Nutr Health 2018; 24(1):5-10.
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