Impacts of Intermittent Fasting on Energy Balance and Associated Health Outcomes
Condition: Obesity; Type 2 Diabetes
Study type: Interventional

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.
    

Detailed description: 
      Recruitment

      Local advertising in the form of posters will distributed throughout the research
      institution, nearby organisations and the city of Bath. The posters will encourage interested
      persons to contact the chief investigator to receive more information on what the study will
      involve. The research team will be looking to recruit 72 (36 lean, 36 overweight/obese)
      individuals who satisfy the entry criteria (discussed later).

      Enrolment

      Potential volunteers will use the contact details provided in advertising materials to
      express their interest to the research team who will then provide them with a copy of the
      participant information sheet to read through at their convenience. Those interested in
      participating will then be invited to a pre-enrolment consultation where they will be given
      the opportunity to ask any questions they may have about the study before being screened for
      the inclusion and exclusion criteria. This will involve measurements of weight and height, as
      well as the completion of an entry criteria questionnaire, the Eating Disorder Examination
      Questionnaire and the Physical Activity Readiness Questionnaire. Providing they satisfy the
      relevant criteria they will be talked through the study and before being asked to complete an
      informed consent form. As part of this, the procedure for an adipose tissue biopsy will be
      discussed with the participant and they will be asked to decide whether or not they would
      like to include this as it is an optional test.

      Baseline Lab Protocol (LAB 1)

      Having formally enrolled in the study, participants will be invited to begin their
      involvement in the study with a 60 minute visit to the University of Bath following a 12 hour
      fast. During this visit, the researcher will obtain a urine sample to check hydration levels
      using an Osmometer, before taking measurements of height, weight and waist circumference. A
      fasting blood sample will also be obtained using venepuncture to measure resting levels of
      key hormones and metabolites. To conclude this visit participants will be asked to perform a
      submaximal exercise test to calibrate the 'Actiheart' monitor being used throughout the study
      to measure physical activity energy expenditure. For this, participants will be asked to
      remain on a treadmill as the intensity increases over the following four stages:

        -  Stage 1 - level walking at 3.2 km/h

        -  Stage 2 - brisk walking at 5.2 km/h

        -  Stage 3 - brisk walking at 5.8 km/h with a steep gradient of +10.2%

        -  Stage 4 - level running at 12.5 km/h

      Stage 4 will only be included for those who are formal exercisers, as non-exercisers are
      unlikely to be doing this kind of activity in their normal routine rendering a calibration at
      this intensity unnecessary. Formal exercisers will be identified using the entry criteria
      questionnaire. In addition, the treadmill protocol will be stopped earlier if the participant
      asks to stop or if their heart rate exceeds 85% of their age-predicted maximum.

      Monitoring Phase

      Before leaving the lab, participants will be provided with an Actiheart monitor, a small
      device applied to the chest which measures physical activity by recording heart rate and
      movement every minute. They will also be provided with a set of kitchen scales and a log book
      to create a weighed record of their food and fluid intake and a set of body weight scales to
      track their weight and help keep it stable.

      During the four week monitoring phase, participants will be asked to complete four 3-day
      monitoring periods, each comprising two weekdays and one weekend day whilst they continue in
      their normal dietary and exercise habits. The researchers will arrange the collection and
      delivery of monitoring equipment where necessary. The purpose of this is firstly to ensure
      weight stability to minimise any confounding influences, secondly to provide accurate
      baseline values for key variables such as physical activity, and finally to ensure the
      dietary records provided are a valid reflection of habitual intake.

      Provided the data obtained in the control phase satisfies the relevant reliability criteria,
      participants will be invited to return to the physiology lab at least four weeks after their
      first visit. In preparation for this, participants will be asked to avoid strenuous exercise,
      alcohol and caffeine, before fasting overnight until they arrive at the lab the following
      morning.

      Pre-Intervention Lab Protocol (LAB 2)

      Before beginning their intervention participants will be asked to attend a pre-intervention
      lab protocol, as outlined below. Female participants will be asked to schedule this so that
      it coincides with the follicular phase of their menstrual cycle (3-10 days after the onset of
      menses) as this is when their hormone profiles are at their most stable.

      On the day of their visit participants will be asked to consume one pint of water at 06:30
      before preparing themselves to arrive at the lab by 07:30, wearing light clothes (i.e.
      shorts, t-shirt) with no metal components or jewellery. They will then need to provide a
      small urine sample to check hydration levels before measurements of height, weight and waist
      circumference are taken (NOTE: If weight varies by more than 1.0 kilograms compared to their
      baseline measurement they may be asked to repeat the monitoring phase).

      At 07:45 participants will be asked to lie in a semi-recumbent position and rest for 30
      minutes. This is in preparation for the measurement of resting metabolic rate and substrate
      oxidation which will be completed at 08:15 over three 5-minute periods using indirect
      calorimetry while the participant remains rested. Following this an intravenous cannula will
      be fitted to the antecubital vein at the elbow for blood sampling throughout the visit. At
      this point a 12 ml fasting blood sample will also be drawn to measure resting levels of key
      metabolites (e.g. glucose, insulin, cholesterol, leptin, ghrelin, etc.).

      At 08:45, participants who have elected to include the adipose tissue biopsy will undergo
      this procedure. If included, an area on the side of the abdomen just above the waistband will
      be sterilised and injected with an anaesthetic (Lidocaine Hydrochloride) to numb the area.
      Using a larger needle a 0.5 gram sample of adipose tissue will then be taken from just below
      the skin. There will some bruising, but if left to heal there should be no scarring. Those
      who choose not to include this biopsy will simply continue resting.

      At 09:00 participants will be asked to complete visual analogue scales (VAS) which will
      provide subjective measures of appetite, fullness and desire to eat. Immediately after this,
      participants will be provided with a test breakfast of instant porridge made with whole milk
      and sugar which they will need to consume within 10 minutes. Key measures will then be taken
      at the following intervals:

        -  12 ml blood sample - 15, 30, 45, 60, 90, 120, 180

        -  Visual analogue scales - 30, 60, 90, 120, 150, 180

        -  Metabolic rate (indirect calorimetry) - 60. 120, 180

      (Note: total urine output will also be quantified throughout the postprandial period to
      adjust substrate oxidation values for protein oxidation)

      At 12:05 participants will be asked to place the hand of their cannulated arm in a padded
      Perspex box which will be heated to 55 degrees. This is to allow the venous blood to be
      arterialised which will provide a better indication of whole body glucose metabolism in the
      test which follows. At 12:15 a 7 ml blood sample will be drawn after which the participant
      will be asked to consume a milkshake which provides 33% of their energy requirements. Blood
      samples (7 ml) will then be drawn every 15 minutes for the ensuing two hours to test for the
      presence of a second meal effect. At 14:15 the final blood sample for this visit will be
      drawn and the cannula will be removed.

      To conclude the pre-intervention protocol participants will be taken to a separate lab for a
      dual-energy x-ray absorptiometry (DEXA) scan. This is a specialized form of whole-body scan
      which measures how a person's weight is distributed between fat and muscle tissue. It takes
      approximately eight minutes and requires the participant to lie still throughout. It does
      administer a small dose of ionizing radiation, but this is equivalent to 7 microSieverts
      which is accompanied by a risk of detrimental radiation effects in the region of 1 in 10
      million. The application of this method has been approved in this study by an independent
      medical physics expert and a clinical radiation expert.

      Intervention Phase

      Before exiting the lab participants will be randomised to one of three treatment conditions
      outlined below. All three diet groups will last for 20 days in total, with transitions
      between each 24 hour cycle occurring at 15:00 each day, the idea being that it will allow
      them to consume at least one main meal per day in all cases. For the intermittent fasting
      groups (IMF), please note that during fasted cycles participants will be asked to only
      consume water and black tea/coffee with no milk or sugar. During feeding cycles, and
      throughout the daily calorie restriction diet, participants will be asked to recreate their
      control phase diet record with appropriately modified quantities to give 75%, 150% or 200% of
      their normal calorie intake in accordance with the group they are assigned to. Where
      recreation is not possible, participants will be asked to note the item that has been removed
      and/or the item that was added in a new diet record that will be provided before they leave
      the lab. Physical activity will also be monitored for the first and last week of the
      intervention using an Actiheart monitor to examine behavioural adaptations to the diets.

        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

      At 15:00 on the day of their initial lab visit, male participants will begin their assigned
      diet, although this can be postponed by up to one week if necessary. Female participants will
      be asked to delay this by six days in all cases in order to ensure their post-intervention
      lab visit falls within the same phase of their menstrual cycle to minimise the impact of
      monthly hormonal fluctuations.

      Post-Intervention Lab Protocol (LAB 3)

      Following the completion of 20 consecutive 24 hour dietary cycles, participants will return
      to their normal diet for one day (prescribed) whilst avoiding strenuous exercise, smoking,
      alcohol and caffeine, before fasting until they arrive at the lab the following morning for
      their post-intervention lab visit. Having consumed a pint of water at 06:30 and arrived at
      07:30 in light clothing, participants will undergo the same lab protocol described earlier
      for their pre-intervention visit. However, instead of being randomised to a diet group they
      will be asked to complete a feedback questionnaire on their experience of the study.

      Follow-up

      Four weeks after their post-intervention lab visit participants will be invited to a feedback
      session to discuss all available results. The results from the meal test and the study as a
      whole will follow at a later date due to logistics and cost-effectiveness. Where convenient
      participants will also be asked to include a weight measurement to provide an indication of
      weight loss sustainability.

      Aim

      Once datasets are obtained for all 72 participants, the daily calorie restriction group will
      be compared against the IMF with weight loss group. This will permit the comparison of the
      effects of an IMF diet against the effects of a more conventional approach when matched for
      energy deficit. The final group, IMF without weight loss, will then highlight the relative
      contributions of weight loss and fasting-dependent mechanisms in producing any observed
      effects.
    

Intervention name(s): Physical Activity Monitoring (Actiheart); Energy Intake Monitoring; Body Weight Monitoring; Intravenous Cannulation; Adipose Tissue Biopsy; Lidocaine Hydrochloride; Post-Prandial Meal Tests; DEXA Scan; Actiheart Calibration; Daily Calorie Restriction; Intermittent Fasting with Weight Loss; Intermittent Fasting without Weight Loss
Intervention type(s): Device; Other; Other; Procedure; Procedure; Drug; Other; Radiation; Other; Other; Other; Other
Intervention description(s): Monitor physical activity using an Actiheart monitor during the required periods.; Monitor energy intake by weighing and recording all foods/drinks consumed during the required periods.; Monitor body weight during monitoring phase to ensure stability despite other monitoring activities.; Fitting of an intravenous cannula to a vein on the forearm for blood sampling during laboratory protocols.; 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.; The anaesthetic that will be used to numb the site of the adipose tissue biopsy in the event it is included.; Consume two successive meals with regular blood samples throughout the ensuing hours (2-3 hours each).; Undergo a dual energy x-ray absorptiometry scan to examine body composition.; Submaximal treadmill test to calibrate monitoring equipment.; Reduce energy intake by 25% on a daily basis.; Alternate between 24 hour cycles of fasting and feeding with 150% of normal intake when feeding.; Alternate between 24 hour cycles of fasting and feeding with 200% of normal intake when feeding.
Intervention MeSH terms: Lidocaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Diet; Fasting; Intermittent Fasting; Alternate-day Fasting; Physical Activity; Glucose; Insulin; Appetite