At visit one, participants were given weighing scales and
instructed to weigh themselves daily and record their
weight on the record card provided. On the record card
at the end of each week there was a box participants
could use to calculate their average weight for the week
to compare to their target weight loss. Daily weighing
was chosen over weekly weighing as immediate feedback
on behaviour might institute the most effective learning
and self-weighing is more likely to become habitual if it
becomes part of a person’s daily routine [21,22].
As this was an explanatory trial we used behavioural
techniques to help participants weigh themselves daily
and are described in detail in Table 1. These techniques
have been categorised based on the CALO-RE behavioural
change taxonomy which is specific to changing
diet and physical activity behaviours [23]. Briefly, the
main technique used was self-monitoring of behavioural
outcome by self-weighing. The benefits of self-weighing
for weight loss were discussed and participants were
instructed to aim for a weight loss of 0.5 kg per week
and to review their average weight loss across the week
against this target. Participants were told to weigh themselves
at the same time every day to help self-weighing
become a habit. They were also instructed to put the
scales in a place which would help them remember to
weigh themselves. Brief weekly text messages were sent
to participants at times participants suggested were appropriate
to prompt them to weigh themselves.
Outcomes
The primary outcome was change in weight from baseline
to three months. Secondary outcomes were physical
activity and weight management strategies; we measured
these as we hypothesised the behaviour of self-weighing
should prompt a change in energy intake or expenditure
based on the review of daily weight [24]. Diet was not
measured as we wanted to reduce participant burden.
Self-weighing frequency was measured objectively in the
intervention group and was self-reported by both groups
at baseline and three months by asking a single question:
‘how often do you usually weigh yourself?’ Due to technical
failures the objective scale data was not available
and we used participants’ daily record cards in the intervention
group to record the frequency of weighing.
At baseline, participants reported socio-demographic
data including: age, gender, ethnicity, postcode (converted
to an index of multiple deprivation score [IMD]),
occupation, medication and long-term health conditions
[25]. IMD is an area-based measure of the socioeconomic
status and scores were categorised into quartiles
[25]. Height was measured at baseline to the nearest
centimetre and weight (kg) measured at baseline and
follow-up on validated scales (SECA 875). If an objective
measure of weight at follow-up could not be obtained
self-reported weight was used. At baseline and followup,
participants completed a questionnaire about weight
management strategies they had used in the past month
(adapted from a questionnaire previously used) and the
international physical activity questionnaire (IPAQshort)
[26,27]. Physical activity was converted into MET
minutes. Participants in the intervention group were
asked on a Likert scale (1-9) if self-weighing affected
their mood or made them change the way they felt
about their body (a score of five being no difference) to
identify any adverse effects. There was an open question
where participants could provide comments about selfweighing