Impact of intermittent fasting on energy balance (v 1.0)

  • Research type

    Research Study

  • Full title

    Impacts of intermittent fasting on energy balance and associated health outcomes



  • Contact name

    Jean-Philippe Walhin

  • Contact email

  • Sponsor organisation

    University of Bath

  • Duration of Study in the UK

    3 years, 7 months, 29 days

  • Research summary

    Obesity is a global concern with prominent links to cardiovascular disease. Historically, these conditions have been managed by reducing energy intake on a daily basis, which is often hampered by low adherence rates and compensatory reductions in physical activity. Intermittent fasting (IMF) has become popular as an alternative method of weight loss, wherein periods of normal consumption are punctuated by days of fasting. However, despite its popularity, IMF is scarcely examined within the published literature. The proposed research will therefore seek to ascertain the impact of IMF on energy balance and the associated health outcomes.

    To achieve this, 36 lean adults and 36 overweight/obese adults will be recruited, excluding those with conditions which may be adversely affected by fasting. Once enrolled, participants will be asked to complete a one month control phase to ensure their weight is stable before being randomised to one of three diets which are listed below. All three diets will last for 20 consecutive days, with transitions between each 24 hour cycle occurring at 15:00 each day.

    1. Daily calorie restriction - Reduce energy intake by 25% on a daily basis
    2. IMF with weight loss - Alternate between 24 hour cycles of fasting and feeding with 150% of normal intake on feeding cycles
    3. IMF without weight loss - Alternate between 24 hour cycles of fasting and feeding with 200% of normal intake on feeding cycles.

    When fasting, participants will only be permitted water and black tea/coffee to eliminate energy intake. Two half-day laboratory visits placed before and after the assigned diet will examine changes in body composition and metabolic responses, whilst energy intake, sugar profiles and physical activity will be monitored during the diet. Although demanding, such an approach is necessary to understand the potential of fasting-based diets and has been applied in a pilot study with no adverse consequences.

  • REC name

    South West - Frenchay Research Ethics Committee

  • REC reference


  • Date of REC Opinion

    9 Feb 2015

  • REC opinion

    Further Information Favourable Opinion