Stuart and Flemming published data from the longest fast, 382 days, on an obese man in Dundee, making it into the Guinness Book of Records, after reaching a 75% WL
We can conclude that fasting is a ‘quick fix’ to achieve a substantial WL (up to 5% loss in 6 days). There is, however, the problem of elevated hunger during food restriction and this may provide too great a challenge to a ‘faster’ in not breaking compliance to the dieting regime and reaching for the biscuit barrel. Also, fasting results in minimal loss of fat tissue, in comparison with other dietary regimes and does involve substantial loss of lean (protein) tissue and this may impact on physiological function. Therefore, short-term fasting may not be a regime that optimizes the health benefits of fat loss per se. During fasting, increased fatigue can reduce spontaneous physical activity by ∼1–2 MJ d−1, and this will ultimately limit negative energy balance and may be seen as counter-productive. Nonetheless, a zero calorie intake does guarantee WL and this overrides some of the impact of reduced energy expenditure. Post WL, it is unclear what mechanisms or behavioural traits promote weight stability and whether fasting could contribute to maintenance of WL in some phenotypes. This continuous fast regime is not suitable for all individuals and would require medical supervision. For medical reasons we cannot promote it as a public health WL strategy. Nonetheless, intermittent fasting remains an intriguing intervention that may provide a novel method of body weight control for certain individuals."