The Intake and Composition of Intermittent Fasting, the 5:2 Method

Abstract

Background: Obesity is a major contributing factor to the development of metabolic disease worldwide, with dietary intervention a primary intervention strategy. Currently, a common approach to weight loss is daily energy restriction (DER), otherwise known as continuous energy restriction (CER). The DER regimen limits energy intake every day and has been proven to be effective at achieving significant weight loss. However, the long-term effectiveness is limited due to decreased adherence over time (1). As a result, new dietary approaches are investigated. Recently intermittent fasting (IF) has become popular as a weight-loss diet. There are multiple versions of intermittent fasting and all of them are popular, due to greater flexibility in regime when compared with traditional weight loss diets. However, the macronutrient and micronutrient intake and composition of the intermittent fasting diet have often been over looked. Objective: The primary aim of this study was to describe the macronutrient and micronutrient intake and composition of the 5:2 method of the intermittent fasting diet (IF 5:2). Additional aims included describing the change in intake from baseline to week six, as well as describing the food and beverages consumed on fasting days. Design: This was a secondary analysis of two previous studies that used IF 5:2 as a dietary intervention. The final analysis included 38 participants, which were overweight and obese, males and females. The dietary intervention was two days per week of fasting, either consecutive or non-consecutive, with an energy intake of 2090-2508 kJ/d. The remaining five days were non-fasting days and participants were advised to have habitual intakes. Prospectively filled out 4-day estimated food records were used to assess dietary intake at baseline and week six. Participants recorded at least one fasting day per week. Intakes were analysed using the computer software program Foodworks (2). Results: During IF 5:2 the macronutrient composition was within the acceptable macronutrient distribution range for protein and fat, above for saturated fat, and below for carbohydrates. Fibre intake was lower than both male and female recommendations. The weighted weekly intake of calcium, zinc, magnesium and potassium during intermittent fasting were lower than recommendations. Furthermore, sodium intakes exceeded the suggested daily target. The intake of all macronutrients and micronutrients, except caffeine, decreased on fasting days. Conversely, the percent of total energy from protein significantly increased (p=0.02). On non-fasting days the energy intake decreased in week six when compared with baseline, despite intake being unrestricted. Additionally, participants intake on fasting days indicates that they followed meal suggestions provided. Conclusion: This composition of IF 5:2 was a high protein, moderate fat, low carbohydrate diet. The intake for fibre and some micronutrients during intermittent fasting were lower than recommendations. Further research is required assessing adequacy of this diet to inform individuals if there are nutritional risks to following it. Currently the 5:2 method of intermittent fasting appears as though it is a suitable alternative weight-loss diet.