Impacts of Intermittent Fasting on Energy Balance and Associated Health Outcomes
Status:
Completed
Trial end date:
2018-09-28
Target enrollment:
Participant gender:
Summary
Obesity is a global concern with links to conditions such as diabetes. 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, where
periods of normal eating are punctuated by days of fasting. However, despite its popularity,
IMF is scarcely examined within the literature.
This study will examine the impact of IMF on energy balance and the associated health
outcomes relating to conditions such as diabetes. 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 complete a one month control
phase, incorporating 12 days of diet and activity monitoring, to ensure their weight is
stable before moving in to the intervention phase.
The intervention phase will begin with a lab protocol designed to examine body composition,
resting metabolic rate and metabolic responses to two successive meals. Once completed,
participants will be randomised to one of three diets which are listed below. Comparing the
changes seen with diets 1 and 2 will provide the first direct comparison of IMF against more
conventional strategies, while diet 3 will allow us to ascertain the role of weight loss in
mediating any effects of IMF.
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 when feeding
3. IMF without weight loss - Alternate between 24 hour cycles of fasting and feeding with
200% of normal intake when feeding
All three diets will last for 20 consecutive days, with transitions between each 24 hour diet
cycle occurring at 15:00 each day to allow at least one main meal per day. When fasting,
participants will only be permitted water and black tea/coffee to eliminate energy intake.
Once again physical activity and diet will be monitored for 12 days during the intervention
to examine changes in energy expenditure and ensure compliance.
Having completed all 20 diet cycles participants will return to the laboratory to repeat the
protocol described earlier. Comparing these results against the values seen before the
intervention will then allow the effects of IMF to be identified and compared.