Determining how best to support overweight adults to adhere to lifestyle change: Protocol for the SWIFT study

Abstract

Background:
Physical activity plays a critical role in health, including for effective weight maintenance, but adherence to guidelines is often poor. Similarly, although debate continues over whether a "best" diet exists for weight control, meta-analyses suggest little difference in outcomes between diets differing markedly in macronutrient composition, particularly over the longer-term. Thus a more important question is how best to encourage adherence to appropriate lifestyle change. While brief support is effective, it has on-going cost implications. While self-monitoring (weight, diet, physical activity) is a cornerstone of effective weight management, little formal evaluation of the role that self-monitoring technology can play in enhancing adherence to change has occurred to date. People who eat in response to hunger have improved weight control, yet how best to train individuals to recognise when true physical hunger occurs and to limit consumption to those times, requires further study.

Methods/design:
SWIFT (Support strategies for Whole-food diets, Intermittent Fasting, and Training) is a two-year randomised controlled trial in 250 overweight (body mass index of 27 or greater) adults that will examine different ways of supporting people to make appropriate changes to diet and exercise habits for long-term weight control. Participants will be randomised to one of five intervention groups: control, brief support (monthly weigh-ins and meeting), app (use of MyFitnessPal with limited support), daily self-weighing (with brief monthly feedback), or hunger training (four-week programme which trains individuals to only eat when physically hungry) for 24 months. Outcome assessments include weight, waist circumference, body composition (dual-energy x-ray absorptiometry), inflammatory markers, blood lipids, adiponectin and ghrelin, blood pressure, diet (3-day diet records), physical activity (accelerometry) and aerobic fitness, and eating behaviour. SWIFT is powered to detect clinically important differences of 4 kg in body weight and 5 cm in waist circumference. Our pragmatic trial also allows participants to choose one of several dietary (Mediterranean, modified Paleo, intermittent fasting) and exercise (current recommendations, high-intensity interval training) approaches before being randomised to a support strategy.

Discussion:
SWIFT will compare four different ways of supporting overweight adults to lose weight while following a diet and exercise plan of their choice, an aspect we believe will enhance adherence and thus success with weight management.

Trial registration:
Australian and New Zealand Clinical Trials Registry ACTRN12615000010594 . Registered 8(th) January 2015.

Full text

S T U D Y P R O T O C O L Open Access
Determining how best to support
overweight adults to adhere to lifestyle
change: protocol for the SWIFT study
Rachael W. Taylor
1*
, Melyssa Roy
1
, Michelle R. Jospe
2
, Hamish R. Osborne
1
, Kim J Meredith-Jones
1
,
Sheila M. Williams
3
and Rachel C. Brown
2
Abstract
Background: Physical activity plays a critical role in health, including for effective weight maintenance, but adherence
to guidelines is often poor. Similarly, although debate continues over whether a “best”diet exists for weight control,
meta-analyses suggest little difference in outcomes between diets differing markedly in macronutrient composition,
particularly over the longer-term. Thus a more important question is how best to encourage adherence to appropriate
lifestyle change. While brief support is effective, it has on-going cost implications. While self-monitoring (weight,
diet, physical activity) is a cornerstone of effective weight management, little formal evaluation of the role that
self-monitoring technology can play in enhancing adherence to change has occurred to date. People who eat in
response to hunger have improved weight control, yet how best to train individuals to recognise when true
physical hunger occurs and to limit consumption to those times, requires further study.
Methods/design: SWIFT (Support strategies for Whole-food diets, Intermittent Fasting, and Training) is a two-year
randomised controlled trial in 250 overweight (body mass index of 27 or greater) adults that will examine
different ways of supporting people to make appropriate changes to diet and exercise habits for long-term
weight control. Participants will be randomised to one of five intervention groups: control, brief support
(monthly weigh-ins and meeting), app (use of MyFitnessPal with limited support), daily self-weighing (with brief
monthly feedback), or hunger training (four-week programme which trains individuals to only eat when physically
hungry) for 24 months. Outcome assessments include weight, waist circumference, body composition (dual-energy
x-ray absorptiometry), inflammatory markers, blood lipids, adiponectin and ghrelin, blood pressure, diet (3-day diet
records), physical activity (accelerometry) and aerobic fitness, and eating behaviour. SWIFT is powered to detect
clinically important differences of 4 kg in body weight and 5 cm in waist circumference. Our pragmatic trial also
allows participants to choose one of several dietary (Mediterranean, modified Paleo, intermittent fasting) and exercise
(current recommendations, high-intensity interval training) approaches before being randomised to a support strategy.
Discussion: SWIFT will compare four different ways of supporting overweight adults to lose weight while following a
diet and exercise plan of their choice, an aspect we believe will enhance adherence and thus success with weight
management.
Trial registration: Australian and New Zealand Clinical Trials Registry ACTRN12615000010594. Registered 8
th
January 2015.
Keywords: Obesity, Adherence, Mobile applications, Hunger, Self-weighing, Intermittent fasting, High-intensity
interval training, Self-monitoring
* Correspondence: rachael.taylor@otago.ac.nz
1
Department of Medicine, University of Otago, PO Box 56, Dunedin 9054,
New Zealand
Full list of author information is available at the end of the article
© 2015 Taylor et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Taylor et al. BMC Public Health (2015) 15:861
DOI 10.1186/s12889-015-2205-4

Background
Overweight and obesity affect almost two-thirds of New
Zealand adults and rates continue to climb in some
ethnic and demographic groups [1]. The inability of
many individuals to lose significant weight by themselves
or for most to keep it off is due to a myriad of factors in-
cluding making changes to lifestyle that are too drastic
and therefore not sustainable, the widespread availability
of energy-dense foods and sedentary past-times, changes
to work and leisure-time energy expenditure, and in-
sufficient support structures [2, 3]. However, consid-
erable debate and confusion also exists in both lay
and scientific literature regarding whether there is an
“optimal”dietary composition for weight loss [4].
Low-carbohydrate diets in particular have long been
purported to have metabolic and clinical advantages
over other dietary patterns [5–7]. It makes mechanis-
tic sense that lower carbohydrate diets could promote
greater weight loss, principally because of a reduction
in insulin levels reducing the storage of body fat [8].
However, at the practical level, recent meta-analyses
suggest little difference in weight and health outcomes
between diets differing quite markedly in macronutrient
composition, particularly over time frames longer
than 6 months [9–13]. Instead, a far more relevant
factor appears to be the degree of adherence to the
prescribed diet [11, 14, 15], an aspect that is insuffi-
ciently measured [16].
Such findings have led expert groups to recommend
that the most suitable diets are not those that include a
specific nutrient composition per se, but rather ones that
entail moderate energy restriction which participants are
willing and able to follow long-term [17]. It is becoming
clear that several acceptable dietary patterns that differ
quite markedly in terms of macronutrient composition
are suitable for weight loss. The more important ques-
tion then becomes how best to encourage and support
long-term compliance with one, or more, of these pat-
terns [18]. However, while adherence to dietary change
is viewed as a cornerstone of non-communicable disease
prevention and management [19], little practical guid-
ance is available identifying which specific factors en-
hance adherence to dietary advice [3]. The short-term
nature of most studies, marked differences in terms of
how adherence is assessed, and overall low trial quality
limits firm conclusions being drawn about the most effi-
cacious factors [3].
Strong social support is considered an important ad-
junct to successful weight loss or maintenance [20]. The
use of personalised support with nutrition and activity
specialists is known to be effective [21], however it is
expensive and rarely accessed. Alternative forms of
low-intensity but regular support, delivered by non-
specialists can result in similar benefits, at a fraction
of the cost [22]. Brief monthly support, such as is
found in many commercial weight loss programmes,
also appears to maintain weight loss better over 2–3
years than other forms of support including inter-
active websites and self-directed control [23]. However,
because such support cannot continue indefinitely, and
ongoing development of innovative technology, deter-
mining the efficacy of other, low-cost strategies is cur-
rently of great interest [24].
Self-monitoring of weight, food intake and/or activity
levels has been shown to be one of the most effective
strategies employed for successful weight management
[25]. However, monitoring of food and activity is time-
consuming and adherence dramatically declines over
time [26]. The advent of mobile “apps”may offer a more
effective way of monitoring food/ activity patterns due
to instant feedback of a wealth of information [27].
While self-monitoring strategies are a common compo-
nent of the myriad of commercially available apps [24],
whether they are effective at encouraging behaviour
change has rarely been examined, despite their wide-
spread use [28]. Although the top five self-monitoring
apps each have a user base of more than 10 million
people [28], only one appears to have been tested in a
clinical trial [29]. Laing et al. [29] recently demonstrated
that use of MyFitnessPal alone, with no accompanying
dietary or exercise advice, did not produce significant
weight change over 6 months in comparison with usual
care. The apparent lack of effect may be due in part to
the sharp declines in adherence to app use after the first
month [29]. Perhaps this is not surprising given that the
response of individuals to self-monitoring can vary
considerably, ranging from the “well-disciplined”who
endorse this approach, to those that have “diminished
support”, where other co-existing factors take prece-
dence [30].
Compared with monitoring of diet or activity, moni-
toring of body weight is both straightforward and quick.
Although weekly or monthly weighing has traditionally
been recommended, observational studies suggest that
daily weighing may promote weight loss better than less
frequent weighing [31–33]. However, few studies have
examined the efficacy of daily self-weighing in compari-
son to less frequent weighing via randomised controlled
trials. Steinberg et al. [34] reported a weight loss of
6.6 % over a 6-month period in the daily weighing group
compared with only 0.4 % in wait-list controls. It may be
that more frequent weighing offers further advantages;
Oshima et al. [35] demonstrated that twice-daily weigh-
ing resulted in greater weight loss than once-daily
weighing in a small group of overweight adults. How
these changes related to changes in actual body compos-
ition is unknown, but important given that it is widely
acknowledged that fat loss, rather than weight loss,
Taylor et al. BMC Public Health (2015) 15:861 Page 2 of 11

provides the key health benefits [36]. Whether such fre-
quent weighing produces adverse psychosocial effects is
a matter of concern. However, the limited data to date
suggest that no adverse effects, and potentially even
some benefits, have been observed, at least over 6–18
months [37–39].
One of the major barriers to effective weight manage-
ment is that we eat for a variety of complex and interre-
lated reasons other than hunger, including taste, social
interaction and emotional cues. Observational studies
demonstrate that many environmental and situational
cues influence our eating [40], but those who eat in re-
sponse to hunger, recognise satiety signals, and give
themselves unconditional permission to eat foods of
their choosing (intuitive eaters), are more likely to be a
healthy weight than those who do not [41, 42]. While
people can be trained to eat more intuitively (in re-
sponse to hunger and satiety), whether this increases
weight loss relative to other techniques remains uncer-
tain [43, 44]. An alternative type of hunger training has
been suggested, where subjects are trained over a few
weeks to identify actual (physiological) hunger by con-
necting the physical feelings of hunger with blood glu-
cose levels [45]. This training has been shown in one
small study to produce significant weight loss compared
with a conventional approach which required constant
dietary restraint [46]. Whether this approach is a viable
way of training individuals to eat to their appetites re-
quires further examination, particularly in terms of its
ability to work over longer time frames.
Testing the effectiveness of different support strategies
should theoretically occur with all participants following
the same diet. However, we know that one of the major
difficulties in trials which randomise people to follow
specific dietary patterns is that any particular diet cannot
possibly suit every individual, which undoubtedly influ-
ences adherence. Behavioural choice theory posits that
outcomes are improved when participants receive the
treatment they prefer [47]. It thus seems feasible that
tailoring a diet on the basis of individual personal and
cultural preferences (i.e. choice) may therefore have the
best chance for long-term success [48], perhaps through
enthusiasm, a better fit with their overall lifestyle, or
supporting personal autonomy. However, whether choice
of intervention group versus randomisation affects ad-
herence and outcomes in weight loss studies has been
examined infrequently, and the findings do not generally
support the theory [49]. There was no evidence of a dif-
ference in outcomes from having a preference for a cer-
tain intervention in terms of group versus individual
treatment [50], low fat versus low carbohydrate diets
[51], or choice of commercial diet programme [52]. The
remaining study found significantly greater weight loss
in those randomised to a diet than in those who were
allowed to choose a diet, although clinically important
weight losses were observed in both groups [53]. How-
ever, many of these studies were relatively small and
were unable to provide precise estimates of effects
[50, 52, 53], or lasted less than one year [50]. Thus
further examination of the impact of being able to
choose which diet or activity plan to follow is war-
ranted, particularly given the high drop-out rates typ-
ically observed in randomised controlled trials of
dietary interventions. This is particularly true given
under real-world conditions, people seeking to lose
weight select their own dietary and/or physical activ-
ity approach(es). Moreover, in reality, switching be-
tween weight loss strategies will occur even when a
particular approach has been suggested by a health
professional or within randomised trials.
Two promising and popular dietary approaches,
despite relatively little research around their use in
humans, include paleolithic diets and intermittent fast-
ing. Paleolithic diets are based on evolutionary principles
and include meat, fruit, vegetables and nuts/seeds while
eschewing grains, dairy, and processed foods. Early small
studies have provided encouraging results [54–56].
However, whether overweight adults can adhere to
paleolithic-type diets in the longer-term requires study.
Intermittent fasting is usually defined as normal food in-
take 3–5 days a week and dramatically reduced intake
(down to 2 MJ from typical intake of 8–10 MJ) for 2–4
days. Anecdotally this is believed to be much easier than
reducing energy intake by a smaller amount (usually
2 MJ/day) every day, which forms part of the current
guidelines. While a wealth of animal data supports the
effectiveness of intermittent fasting for weight control
[57], research in humans is less certain [58]. However,
the small amount of data available does show modest
evidence of effectiveness for treatment of obesity and
cardioprotection [59, 60].
Exercise produces more successful weight loss than
dietary change alone [61, 62], seems particularly import-
ant for weight maintenance [63] and has many add-
itional health benefits, over and above that relating to
energy balance. Regular physical exercise is associated
with an approximate halving in the risk of cardiovascular
disease [64], can decrease the incidence of diabetes by
up to 50 % as part of lifestyle counselling [65], and even
decrease insulin resistance in those with established
metabolic syndrome [66]. However, a major public
health challenge is how best to encourage people to be
physically active on a regular basis. Although evidence
that regular physical exercise is beneficial is overwhelm-
ing [67], adherence remains a major issue [68], with lack
of time often cited as a major barrier [69]. Thus there
has been increasing interest in ascertaining the mini-
mum amount of exercise required that might produce
Taylor et al. BMC Public Health (2015) 15:861 Page 3 of 11

effective health benefits. An alternative to meeting mod-
erate to vigorous physical activity (MVPA) guidelines
may be the promotion of high intensity interval training
(HIIT). In HIIT, brief periods of high-intensity exercise
are interposed with recovery periods at a much lower in-
tensity [70]. Although HIIT regimes typically include
10 minutes or so of intense exercise performed three
times per week, as little as 3 minutes of intense exercise
per week has been shown to produce cardiovascular and
metabolic improvements [71, 72], although effects on
body composition are less certain [73]. Although HIIT
holds promise, virtually all research to date has been
conducted in the laboratory and it is uncertain whether
these findings will translate into community settings. If
people cannot complete HIIT by themselves, its efficacy
as a public health approach is very limited. Whether par-
ticipants can adhere to a HIIT training regime long-
term is also not currently known.
Aims and objectives
The goal of our study is to determine whether allowing
participants to choose from a selection of appropriate
diet and exercise plans, within the context of a rando-
mised controlled trial evaluating four different support
strategies, enhances adherence and promotes greater
weight loss and positive health outcomes. Giving people
the choice of which diet and exercise regime is best in-
corporated into their particular lifestyle is expected to
improve adherence, reflects real-world conditions, and is
consistent with the lack of evidence for meaningful dif-
ferences between diet modalities. Acknowledging this
concept in conjunction with testing different support
strategies offers a unique opportunity to determine how
best to support individuals to make dietary and exercise
changes under real-world conditions.
The primary aim of our study is to determine the
effectiveness of different support strategies (control con-
dition, brief support, daily self-weighing, app use, hunger
training) on weight loss at 12 and 24 months. Secondary
aims are to determine:
(i) the effect of different support strategies on body
composition, dietary intake, exercise, inflammatory
markers, blood lipids and lipoproteins, adiponectin,
ghrelin, and psychosocial indices at 12 and
24 months
(ii) the degree of adherence to each of the support
strategies over the 24 months
(iii) the degree of adherence to each of the diet
(Mediterranean, intermittent fasting, modified
Paleo) and exercise (current recommendations,
HIIT) plans that are selected over the 24 months
and the outcomes within these self-selected
groups.
Methods/Design
Study design
The Support strategies for Whole food diets, Intermittent
Fasting and Training (SWIFT) study is a 5-arm rando-
mised controlled trial testing the effectiveness of differ-
ent support strategies for encouraging appropriate
behaviour change for effective weight management. Par-
ticipants will be randomised to one of the five groups
for a 12-month intervention, with further follow-up at
24 months (Fig. 1) to determine whether any changes
have been sustained. The primary analysis will be modi-
fied intention to treat (using all available data) and will
focus on the outcomes resulting from the different sup-
port strategies (RCT analysis).
The trial has been approved by the University of Otago
Human Ethics Committee (H14/024) and is registered
with the Australian New Zealand Clinical Trials Registry
ACTRN12615000010594. Written informed consent will
be obtained from all participants before randomisation.
Participants and recruitment
Recruitment will occur by advertisement (flyers, newspa-
pers, email distribution lists) and word of mouth and in-
terested people will be directed to complete an online
screening questionnaire. They will be deemed eligible to
attend a screening appointment if they indicate that they
are at least 18 years of age, their self-reported body mass
index (BMI) is greater than 27, they have internet access,
they intend to remain in the local area for the duration
of the 2-year intervention, and if female, they are not
planning to become pregnant in next two years nor are
currently breastfeeding, and have no history of cardio-
vascular or other serious medical conditions. Presence of
symptoms suggesting undiagnosed heart disease and
current medication use will be reviewed by medical
staff. Further exclusions will occur for diabetes melli-
tus type 1 and 2, endocrine disorders, systemic in-
flammatory diseases and musculoskeletal disorders
preventing exercise. People with stage one hyperten-
sion, dysglycaemia and mild controlled asthma will
be potentially eligible.
Screening appointment
Potentially eligible participants will attend a screening
session following a 12-hour overnight fast. Duplicate
measurements of height, weight, and systolic/diastolic
blood pressure will be undertaken using standard tech-
niques and venepuncture blood samples will be collected
by a registered nurse. Participants will complete a com-
prehensive baseline questionnaire, and be instructed on
how to complete a 3-day weighed diet record over the
next week. Participants will also wear an Actigraph ac-
celerometer for 7 days and nights to assess physical ac-
tivity and sleep during the same time period. Further
Taylor et al. BMC Public Health (2015) 15:861 Page 4 of 11

exclusion criteria will be applied at this point: measured
BMI less than 27, fasting blood glucose greater than
7 mmol/L (if randomised to hunger training, fasting
blood sugars consistently above 7 mmol/L would result
in difficulties for the participant to adhere to hunger
training guidelines), systolic BP greater than 160 mmHg
or diastolic BP greater than 100 mmHg (because they re-
quire medical management for their hypertension). All
participants will also undergo a dual-energy x-ray ab-
sorptiometry (DXA) scan at baseline (see outcome
measures).
Exercise safety screening
All participants will undergo medical screening by ques-
tionnaire to allow identification of those at higher risk of
an adverse event during exercise. High-risk participants
with known or likely occult heart disease will be ex-
cluded. Participants who choose high intensity regimes
will be individually medically assessed and be stratified
into categories of risk for cardiovascular events as per
American College of Sports Medicine/American Heart
Association (ACSM/AHA) guidelines [74]. Participants
who are considered to be in a moderate-risk category
who wish to participate in high-intensity exercise pro-
grammes will have a focussed medical examination, as
per current ACSM guidelines.
Choice of diet and exercise plan
If a participant is eligible and has completed all baseline
assessments, they will be provided with information on
each of the possible three dietary and two exercise ap-
proaches, and allowed to choose which might suit them
best.
Their choice of dietary approaches will be:
1) Mediterranean –High amounts of fruit, vegetables
and wholegrain cereals, moderate amounts of
protein (particularly from fish), nuts (up to 30 g
per day), olive oil and dairy foods, and limited
amounts of processed and sugary foods. Calorie
counting will not be required (unless randomised
to MyFitnessPal), but energy intake should be
reduced by appropriate levels through promotion
of appropriate foods and serving sizes.
2) Modified paleolithic –Strict paleolithic diets remove
all processed and cereal-based foods, legumes and
dairy products which we believe is not sustainable
for most overweight people long-term. Participants
who choose this diet can decide to remove these
foods; but we will also suggest they follow an 80:20
rule where up to one serving of dairy products,
legumes and appropriate low glycaemic index,
wholegrain carbohydrates are allowed each day.
Fig. 1 Overview of the study design including choice of diet/exercise plan and randomisation to support strategy
Taylor et al. BMC Public Health (2015) 15:861 Page 5 of 11

We believe this still fits the paleolithic philosophy
while promoting greater long-term adherence through
flexibility. Calorie counting will not be required (unless
randomised to MyFitnessPal), but energy intake should
be reduced by appropriate levels through promotion of
appropriate foods and serving sizes.
3) Intermittent fasting (5:2 plan) –Participants choose
two days per week (any days, not consecutive, can
vary from week to week to fit lifestyle) where energy
intake cannot exceed 2 (females) –2.5 (males) MJ.
In practice, this usually means a small breakfast
(e.g. plain porridge), no or limited food during
the day, and non-starchy vegetables only for the
evening meal, although other variations are possible.
Participants can eat ad libitum on the remaining days.
The choice of exercise approaches will be from:
1) Current New Zealand guidelines –recommend that
participants engage in “at least 30 minutes of
moderate intensity physical activity on most if not
all days of the week. If possible, add some vigorous
exercise for extra health benefit and fitness”
(http://www.health.govt.nz/our-work/preventative-
health-wellness/physical-activity). Standard
printed resources available from the Ministry of
Health will be used for counselling with this
group. Typical recommended activities include
walking briskly, exercise classes, and gardening
but no mention is made of HIIT type activities
(brief sessions of very high intensity exercise).
2) Home-based high-intensity interval training (HIIT) –
Those choosing HIIT attend a private 1-hour
training session which includes focused medical
evaluation and HIIT training (cycle ergometer)
using rating of perceived exertion in combination
with heart rate monitoring. This typically includes 3
intervals of durations of up to 30 seconds, including
two maximal sprint intervals. Fitness is likely to vary
amongst participants at baseline, so clinical judgment
is required to adapt the initial training of participants
who have low baseline cardiorespiratory fitness
or other significant issues influencing exercise
tolerance. However, it is intended that all participants
experience at least one observed interval that achieves
80-90 % of their estimated maximum heart rate
which allows the participant to recognise the
required intensity, and for further identification of
any undisclosed cardiac symptoms. Participants then
use heart rate monitors to record unsupervised
HIIT sessions for another week, ensuring further
confirmation that the required intensity is being
achieved. Training and resources are then provided
outlining how HIIT can be achieved at home.
Four different protocols are provided including a
“beginners”HIIT protocol (e.g. 10 second intervals
at 90 % intensity repeated 3–5times),andthen
three harder options. These include maximal
(90 % maximum heart rate) and submaximal
(80 %) options, involve a variety of interval lengths
(e.g. 30 seconds to 4 minutes), and number of repeats
(3–10 times) [70,72,75,76]. In general, participants
will be encouraged to gradually increase their
HIIT from a beginners level to ultimately being
able to complete three approximately 15-minute
(allowing for warm-up and cool-down) sessions
of HIIT each week following one of the submaximal
or maximal options. A variety of possible exercises
are suggested including sprinting, stair climbing,
exercise equipment such as exercycles or rowing
machines, and activities such as star jumps, burpees
and the like, as long as it is “exercise that uses most
of your body and is very hard to do within seconds”.
Partictipants could also choose to do high intensity
sports sessions that involved sprint intervals, or use
commercial gym-based HIIT classes as acceptable
alternatives.
An additional resource will be provided to all partici-
pants which focuses on evidence-based behavioural
weight loss strategies known to be successful, including
stimulus control, problem solving, stress reduction and
dealing with negative thinking [77].
Randomisation
Once participants have chosen their diet and exercise
approach, randomisation will occur using sequentially
numbered opaque sealed envelopes prepared by the stat-
istician. The participants will be stratified by sex and
random length blocks will be used to allocate the treat-
ment. Participants will then be booked into their first
intervention session.
Intervention groups and sessions
1) Control –those randomised to the control condition
will meet with research staff to discuss which
diet and exercise options would suit them best.
They will also receive the resource detailing the
evidence-based behavioural weight loss strategies
noted above. They will then be left to their own
devices for the remainder of the study (except
for attending all outcome assessments).
2) Regular brief support –Participants in this group
will attend an appointment at the study clinic once a
month to be weighed. During this time they will
have the opportunity for a 5–10 minute conversation
with research staff to assess progress, review and
Taylor et al. BMC Public Health (2015) 15:861 Page 6 of 11

brainstorm solutions to problems if any exist, and
encourage adherence. These sessions are modelled on
our successful HEAT study and provide an opportunity
for support and ongoing assistance with strategies [22].
3) App –Participants in the app group will attend an
appointment to learn how to use MyFitnessPal to
monitor their energy and macronutrient intakes.
They will be provided with assistance in setting up
their MyFitnessPal account to be compatible with
their chosen diet, and will be shown how to use
the app on their smartphone and/or computer.
Participants will be asked to monitor their dietary
intake every day for the first month, and for one
week of every month for months 2–12.
4) Daily self-weighing –Individuals randomised to this
group will receive instruction and support about
weighing themselves every day (same time of day
and degree of clothing). Participants will text their
weight or enter it online using a web page connected
to our secure database each day which will have a
graphical display. Progress and adherence to entering/
sending weight data will be checked every week and
reminder texts sent where necessary. Every month,
research staff will provide personalised progress
feedback and support by email.
5) Biochemical hunger training –This group will follow
a 4-week protocol that trains them to recognise “real”
(biochemical) hunger by associating feelings of hunger
with blood glucose levels following fingerprick testing
with portable glucometers. Our protocol is based on
that of Ciampolini et al. [45] but adapted slightly
following piloting. In the original method, participants
are only able to eat if blood glucose is less than
4.7 mmol/L [45]. Our pilot testing showed that
use of an individualised blood glucose cut-off
(average of fasting blood glucose over two days)
rather than 4.7 mmol/L improved adherence to
testing and reduced eating when blood glucose
was not below the cut-off [78]. Before every desired
eating occasion, participants will be instructed to note
their intensity of hunger on a 100mm visual analogue
scale and their measured blood glucose. If their blood
glucose is higher than their personal cut-off, they are
advised to engage in some other activity as a distrac-
tion and wait at least one hour. At this time, they as-
sess their feelings of hunger again and repeat the
measurement if they still want to eat, until their blood
glucose is under their individualised cut-off. Over
time, participants learn to relate physical feelings of
hunger with their blood glucose and to eat only
when physically hungry. Participants will be advised
to follow this procedure for two weeks. In weeks 3
and 4, the blood glucose testing is optional, but all
other recording (intensity and type of hunger, and
resulting food intake) continues. Participants will be
in regular contact with support staff, who will advise
them how to proceed, answer any queries and provide
encouragement. In months 2–12, participants will be
advised to repeat the recording process (with or with-
out fingerprick blood glucose testing) for one week of
every month.
Outcome assessments
Outcome assessments will occur at 0 (baseline), 6 (mid-
point of intervention), 12 (end of intervention) and 24
(end of follow-up) months as shown in Table 1. Adher-
ence measures are more frequent as outlined elsewhere.
Anthropometry and body composition
All measures (except DXA) will be obtained in duplicate
by trained assessors blinded to support group allocation.
If duplicate measures differ by more than 1 %, a third
measurement is obtained and the median is used as the
final value. Height will be measured by fixed stadiometer
Table 1 Timing of outcome assessments in the SWIFT study
*
Outcome Month
0
†
61224
Height x
Weight
§
xxx x
Bioimpedance x x x x
DXA scan x x
Blood pressure x x x x
Blood samples x x x
3-day diet record x x x x
Accelerometry x x x x
Aerobic fitness x x x x
Questionnaires x x x x
Demographics x
Personality x
Resilience x
Dieting and weight history x
Intuitive eating x x x x
Dutch eating behaviour questionnaire x x x x
Depression, anxiety, stress x x x
Disordered eating x x x
Self-monitoring x x x x
Self-efficacy x x x x
Satisfaction with diet and exercise x x x
*
Two visits are required at each time point in order to complete
all measurements
†
0 refers to baseline
§
More frequent weights will be available for those in the regular brief support
and daily self-weighing groups but these are for adherence measures rather
than outcomes
Taylor et al. BMC Public Health (2015) 15:861 Page 7 of 11

(Heightronic, QuickMedical, WA, USA) and weight by
electronic scales (Tanita BC-418) with participants wear-
ing light clothing and no shoes. Waist circumference will
be measured at the narrowest point between the lower
costal border and the top of the iliac crest by non-elastic
tape. Body composition will be measured by segmental
Bioelectric Impedance Analysis (BIA, Tanita BC-418) at
each time point and by dual energy x-ray absorptiometry
(Lunar Prodigy) at 0 and 12 months only. Measures of
systolic and diastolic blood pressure will be obtained
using an automated sphygmomanometer (Omron Model
HEM-907).
Blood tests
Blood samples will be collected from participants by a
registered nurse following a 12-hour overnight fast.
High-sensitivity CRP will be measured using a CRP
Unimate kit from Roche Diagnostics on a Cobas
Mira Plus Analyzer (Roche), Interleukin-6 by using
Quantikine ELISA Kits (R&D Systems) following the
instructions provided by the manufacturer, adiponec-
tin by radioimmunoassay (Linco Research, St Charles,
MO, USA), ghrelin (active) by immunoassay (Human
Gut Hormone Panel LINCOplex Kit, LINCO Research,
St. Charles, MO, USA), and plasma total cholesterol
(TC), HDL cholesterol (HDL-C), and TG concentrations
by enzymatic methods using a Cobas Mira Plus Analyzer.
LDL cholesterol (LDL-C) will be calculated using the
Friedewald formula [79].
Diet, physical activity and fitness
Participants will complete a weighed 3-day diet record
(one weekend day, two week days) with energy and nu-
trient intakes calculated using Kai-culator (University of
Otago, 2011). Physical activity (counts per minute and
intensity categories) and sleep duration and timing
(minutes, bed time, wake time) will be measured using
ActiGraph accelerometers (GT3X, ActiGraph, Pensacola,
FL) worn around the waist over 7 days. Participants wear
the accelerometers for the full 24-hour periods, which
provides both sleep and activity data and lowers the
chance of missing data from participants not remember-
ing to reattach the accelerometer straight after waking.
Aerobic fitness will be evaluated by estimating partici-
pants’VO
2
max, using the YMCA submaximal cycle erg-
ometer test [80].
Questionnaires
Demographic information (age, sex, education, ethnicity,
employment, income, household structure) will be ob-
tained at baseline using the relevant New Zealand census
questions (http://www.stats.govt.nz/Census). Other ques-
tionnaires to be completed at baseline only include the
Ten-item personality inventory [81] which gives broad
scores for the ‘Big Five’personality dimensions, the Brief
Resilience scale [82] which assesses the ability to bounce
back or recover from stress, and the Dieting and weight
history questionnaire [83]. Questionnaires completed at
baseline, and repeated at 6, 12 and 24 months (not all
measures at all time points) will include the Intuitive
Eating scale [84] which measures the tendency to follow
hunger and satiety cues when eating, the Dutch Eating
Behavior questionnaire [85] which evaluates dietary re-
straint and emotional and external eating, the Depression
Anxiety Stress scale (DASS21) [86], a well-accepted short
measure of depression, anxiety and stress, the Disordered
Eating questionnaire EDE-Q [87] investigating restraint
and concerns about eating, shape and weight, a self-
monitoring questionnaire [39], assessing how often they
weigh themselves and track their eating and physical activ-
ity, selected questions on perceived benefits, self-efficacy
and enjoyment of physical activity, self-efficacy for health
eating and behavioural skills used for weight management
[88] and satisfaction with the dietary and exercise ap-
proaches chosen.
Adherence
Adherence to support strategies will be assessed as
follows:
Brief support: attendance at monthly sessions.
App use: frequency, consistency, and comprehensive-
ness of food recording during first month (daily) and for
one week every month for months 2–11 inclusive.
Daily-self weighing: by the number of daily weights
recorded in the database.
Hunger training: analysis of the 4-week booklets in
month 1 and the weekly recordings for months 2–12 the
percentage of times participants measured their glucose
before eating, and only ate if blood glucose was lower
than the personal cut-off.
Adherence to the dietary regimes will be measured
using the 3-day diet records. Those choosing to follow
intermittent fasting will complete a 4-day diet record at
6, 12 and 24 months to allow collection of two fasting
and two non-fasting days. Adherence to the exercise
regime will be measured by the accelerometers. In
addition, HIIT participants will wear a Polar RC3 GPS
heart rate monitor during all home HIIT sessions for a
one-week period at baseline, 3, 6, 9 and 12 months to
evaluate intensity attained during the sessions.
Statistical analyses and power calculations
Based on a standard deviation (SD) for baseline weight
of 15 kg, and a correlation between repeat measures of
r = 0.90 (obtained from our previous studies involving
similar populations), our study has 90 % power using a
two-sided 5 % level of significance to detect a clinically
important difference in change in body weight of 4 kg
Taylor et al. BMC Public Health (2015) 15:861 Page 8 of 11

between any pair of groups with 42 participants per
group. While this may be viewed as a large difference,
anything smaller does not really represent a difference
of any importance between strategies. Thus we will re-
cruit 250 participants in total across the five groups
which allows for 15 % drop-out/unusable data. Fifty per
group at baseline also provides 80 % power to detect
differences of 5 cm in waist circumference (baseline
SD 12, r = 0.80).
The primary analysis will follow modified intention-to-
treat principles (using all available data) and will com-
pare the outcomes resulting from the five different
support strategies (RCT analysis). Linear mixed models
will be used to model outcomes at 6, 12 and 24 months
after adjusting for baseline values. Standard mixed
model diagnostics will be performed. Although this ana-
lysis does not take diet and exercise choice into account
because meta-analyses show there is little difference in
outcomes from different treatments, further analysis
adjusting for diet and exercise will be considered.
However, because participants do have choice over
which diet and exercise plan they would like to follow,
we are able to investigate the data in a number of ways.
The baseline data will allow a cross-sectional analysis to
assess the popularity of approaches among participants
and then to examine what it is about people that lead
them to choose to follow these different diet and exer-
cise approaches (subject to sufficient numbers choosing
each approach). Once the RCT analysis has been com-
pleted, we will be able to undertake a cohort analysis to
determine whether adherence differs for each of the
different diet and exercise approaches, subject to suffi-
cient numbers making that particular choice, and how
this differing adherence affects our study outcomes of
interest.
All analyses will be performed using Stata 13.1 or a
later version with all statistical tests performed at the
two-sided 0.05 level.
Discussion
Despite continued debate regarding which diet is best
for weight loss, it is becoming increasingly apparent that
a variety of possible diets, ranging in macronutrient con-
tent, are suitable healthy options [17]. A more pressing
issue thus becomes determining how best to support
people to follow one of these approaches [89]. Determin-
ing whether high-intensity exercise can be a viable pub-
lic health approach to improving weight and health is
also warranted, particularly given an intriguing recent
finding that MVPA is more consistently associated with
body weight than is diet quality [90]. The SWIFT trial
aims to compare five (including a control group) differ-
ent ways of helping people to follow one of several pos-
sible dietary and exercise combinations, a choice that we
believe should enhance adherence and thus success with
weight management. We believe our trial offers a prag-
matic way of assessing whether simple support strat-
egies, that require limited to no expert involvement, are
viable ways for overweight adults to successfully manage
their weight over a two-year period.
Competing interests
The authors declare that they have no competing interests.
Authors’contributions
RT is the Principal Investigator of SWIFT, will have overall responsibility for
the project, and wrote first and subsequent drafts of the manuscript. MR and
MJ will undertake the intervention. RB is responsible for the dietary aspects
of the study, KM-J will undertake the body composition assessments, and
MR and HO will oversee the medical aspects of the project. SW designed the
statistical plan and will undertake all statistical analyses. All authors are
co-investigators and provided expert input into the design of the study
and ongoing advice and support. All authors have read and approved
the final manuscript.
Acknowledgements
Funding for the SWIFT project was obtained from a private bequest. The
funder was not involved in the study design and will not contribute to data
collection, analysis, interpretation of data or manuscript drafting and
submission.
Author details
1
Department of Medicine, University of Otago, PO Box 56, Dunedin 9054,
New Zealand.
2
Department of Human Nutrition, University of Otago, PO Box
56, Dunedin 9054, New Zealand.
3
Department of Preventive and Social
Medicine, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
Received: 28 January 2015 Accepted: 2 September 2015
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Taylor et al. BMC Public Health (2015) 15:861 Page 11 of 11