Impacts of Intermittent Fasting on Energy Balance and Associated Health Outcomes

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.

Conditions

• Obesity
• Type 2 Diabetes

Interventions

DEVICE

Physical Activity Monitoring (Actiheart)

Monitor physical activity using an Actiheart monitor during the required periods.

OTHER

Energy Intake Monitoring

Monitor energy intake by weighing and recording all foods/drinks consumed during the required periods.

OTHER

Body Weight Monitoring

Monitor body weight during monitoring phase to ensure stability despite other monitoring activities.

PROCEDURE

Intravenous Cannulation

Fitting of an intravenous cannula to a vein on the forearm for blood sampling during laboratory protocols.

PROCEDURE

Adipose Tissue Biopsy

This is an optional feature which if included involves the removal of a 0.5 gram sample of adipose tissue from just below the skin using a needle.

DRUG

Lidocaine Hydrochloride

The anaesthetic that will be used to numb the site of the adipose tissue biopsy in the event it is included.

OTHER

Post-Prandial Meal Tests

Consume two successive meals with regular blood samples throughout the ensuing hours (2-3 hours each).

RADIATION

DEXA Scan

Undergo a dual energy x-ray absorptiometry scan to examine body composition.

OTHER

Actiheart Calibration

Submaximal treadmill test to calibrate monitoring equipment.

OTHER

Daily Calorie Restriction

Reduce energy intake by 25% on a daily basis.

OTHER

Intermittent Fasting with Weight Loss

Alternate between 24 hour cycles of fasting and feeding with 150% of normal intake when feeding.

OTHER

Intermittent Fasting without Weight Loss

Alternate between 24 hour cycles of fasting and feeding with 200% of normal intake when feeding.

Sponsors & Collaborators

• University of Bath

  lead OTHER

Principal Investigators

• James A Betts, BSc., Ph.D · Fellow of the American College of Sports Medicine

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

NONE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

65 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2015-05-31

Primary Completion

2018-09-04

Completion

2018-09-28

Countries

• United Kingdom

Study Locations