The effects of the 5:2 intermittent fasting diet and sprint interval training on body composition and markers of cardiovascular and metabolic health in overweight individuals

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Deasy, William (2020) The effects of the 5:2 intermittent fasting diet and sprint interval training on body composition and markers of cardiovascular and metabolic health in overweight individuals. PhD thesis, Victoria University.


The global prevalence of obesity has increased almost threefold in recent decades, predicated on the increased availability of energy dense foods, decreased physical activity and the increasingly sedentary nature of the modern workforce. The 5:2 intermittent fasting diet (IF) and sprint interval training (SIT) are two time efficient and easy to follow strategies that have recently become popular alternatives to CR and MICT strategies for weight loss. The efficacy of IF and SIT on weight measurement and health outcomes have been demonstrated separately but the combined effects of these protocols (IFSIT) are currently unknown. Therefore, the purpose of this thesis is to investigate the effects of these protocols (individually and in combination) on body composition, as well as cardiovascular and metabolic risk factors associated with obesity in a free-living, adult population. Additionally, this thesis will investigate the effects of these protocols on mood state, satiety and activity levels to further understand the wider effects of these strategies on motivation and wider health. Thirty-four participants were randomised into three groups (fasting only, SIT only & a combined protocol). The 5:2 protocol uses 2 non-consecutive days of severe energy restriction interspersed with 5 days of ad libitum food consumption per week. The SIT protocol used in the current study used 20 seconds of supramaximal exercise (150% VO2max) interspersed with 40 seconds of active rest over 3-6 cycles. VO2 testing was carried out using a ramped load program on an electrically braked cycle ergometer. Body composition was assessed using DEXA and pqCT and blood analysis was performed following an overnight fast and analysed either commercially or using enzyme-linked immunosorbent assay. The findings of this thesis demonstrate that following a 16-week intervention in an unrestricted, free-living population that IF, with or without SIT, has reduced body weight (IF= -4.1 kg, IFSIT= -4.5 kg), BMI (IF= -1.4, IFSIT= -1.6) and fat mass (IF= -3.3 kg, IFSIT= -2.9 kg) , whilst SIT alone had little effect on these parameters despite significant effects being reported in other studies. Interestingly, IFSIT led to a greater loss of lean mass when compared to IF alone (IF= -0.75 kg, IFSIT= -1.8 kg). Additionally, significant increases to VO2peak (ml/kg.minute) (SIT= +2.1, IFSIT= +4.6) in both exercise groups were observed. However, there was little improvement to other cardiovascular risk factors such as arterial compliance, blood pressure measurements or lipid profiles. Significant decreases in serum leptin levels were recorded in both the IF and IFSIT groups when compared to the SIT group, with little change in other parameters such as glucose tolerance, fasting glucose, HBA1c and other metabolic hormone levels. Additionally, there was no significant effects on mood state, satiety, quality of life measurements, attitudes to food or total activity levels recorded in any group. In conclusion, this thesis is one of the first to demonstrate that the 5:2 diet is effective in the reduction of body weight, leptin levels, BMI and fat mass in a free-living population, whilst SIT had no impact on whole body adiposity despite improvements to VO2peak measurements. When combined with the 5:2 diet, sprint interval training led to greater reductions in lean muscle mass when compared IF alone but otherwise produced no further additive effects. These data suggest that the 5:2 diet is an effective and safe alternative to more traditional energy restriction diets for weight loss in free living adult population.

Item type Thesis (PhD thesis)
Subjects Historical > FOR Classification > 1106 Human Movement and Sports Science
Historical > FOR Classification > 1111 Nutrition and Dietetics
Current > Division/Research > Institute for Health and Sport
Keywords 5:2 diet; fasting; interval training; body composition; intermittent fasting diet; IF; sprint interval training; SIT; body weight; BMI; leptin
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