A randomized controlled trial to isolate the effects of fasting and energy restriction on weight loss and metabolic health in lean adults

Iain Templeman, Harry Smith, Enhad Chowdhury, Yung Chih Chen, Harriet Carroll, Drusus Johnson-Bonson, Aaron Hengist, Rowan Smith, Jade Creighton, David Clayton, Ian Varley, Leonidas Karagounis, Andrew Wilhelmsen, Kostas Tsintzas, Sue Reeves, Jean-Philippe Walhin, Javier Gonzalez, Dylan Thompson, James Betts

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Intermittent fasting may impart metabolic benefits independent of energy balance by initiating fasting-mediated mechanisms. This randomized controlled trial examined 24-h fasting with 150% energy intake on alternate days for 3 weeks (0:150; n=12). Control groups involved a matched degree of energy restriction applied continuously without fasting (75% energy intake daily; 75:75; n=12) or a matched pattern of fasting without net energy restriction (200% energy intake on alternate days; 0:200; n=12). Primary outcomes were body composition, components of energy balance, and post-prandial metabolism. Daily energy restriction (75:75) reduced body mass (-1.91+/-0.99 kg) almost entirely due to fat loss (-1.75+/-0.79 kg). Restricting energy intake via fasting (0:150) also decreased body mass (-1.60+/-1.06 kg; p=0.46 versus 75:75) but with attenuated reductions in body fat (-0.74+/-1.32 kg; p=0.01 versus 75:75), whereas fasting without energy restriction (0:200) did not significantly reduce either body mass (-0.52+/-1.09 kg; p≤0.04 versus 75:75 & 0:150) or fat mass (-0.12+/-0.68 kg; p≤0.05 versus 75:75 & 0:150). Post-prandial indices of cardiometabolic health and gut hormones, along with the expression of key genes in subcutaneous adipose tissue, were not statistically different between groups (p>0.05). Alternate-day fasting less effectively reduces body fat mass than a matched degree of daily energy restriction and without evidence of fasting-specific effects on metabolic regulation or cardiovascular health.
Original languageEnglish
Article number598, eabd8034
Number of pages15
JournalScience Translational Medicine
Issue number598
Publication statusPublished - 16 Jun 2021

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