Globally, overweight and obesity are significant contributors to morbidity and mortality [1
]. Traditionally, behavioural weight loss interventions aim to increase physical activity, improve diet quality and reduce total energy intake to promote weight loss [2
]. Although traditional weight loss interventions achieve modest short-term weight loss (e.g., <3.80 kg over 6 months) relative to control groups [3
], improving sleep in combination with physical activity and diet has the potential to contribute to greater weight loss than interventions only targeting physical activity and diet [5
]. This is relevant as between 20 and 30% of adults engage in a pattern of behaviours characterised by low levels of physical activity, poor dietary behaviours and insufficient sleep [8
Optimal sleep health is characterised by duration, quality and timing of sleep that leaves a person satisfied with their sleep and alert during the day [9
]. Potential mechanisms linking sleep with weight regulation include reduced activity levels among people with short duration or poor quality sleep [10
]. Shorter sleep duration (<5.5 hrs/night) is also associated with increased energy intake, greater likelihood to select energy-dense foods, and poorer regulation of hunger [12
]. Additionally, having poorer quality, shorter sleep duration (<7 hrs/night), or sleep-disordered breathing at the start of a traditional weight loss intervention is associated with lower weight loss in intervention studies [15
]. However, these studies did not specifically aim to improve sleep as part of the intervention [15
]. To our knowledge, only one study has examined how improving sleep, in combination with physical activity and diet, influenced weight loss in adults [5
]. This study reported greater weight loss from a physical activity, diet and sleep health intervention (5%) compared to an intervention without a sleep component (2%) [5
]. The sleep component of the combined intervention commenced in week 4 of the 12-week intervention, potentially limiting the improvements in sleep and reducing potential impacts on weight loss [5
]. Despite these promising results, further research is necessary to examine how improving sleep influences weight loss over longer periods of time.
Due to the high prevalence of overweight and obesity, it is important that intervention approaches have the potential for wide reach and access [3
]. Interventions which include electronic components such as e-health (i.e., website) and m-health (i.e., apps) offer opportunities for delivering behavioural and weight loss interventions in a format that is scalable, and allow participation at times that are convenient to individuals [18
]. Few (n
= 4) m-health interventions target physical activity, diet and sleep behaviours in combination, and none have focussed on weight loss [20
]. The primary aim of the current study was to compare the efficacy of two multi-component m-health interventions pooled together with a wait-list Control group on body weight (primary outcome) and secondary outcomes including cardiovascular risk factors (i.e., waist circumference, HbA1c), behaviours (i.e., physical activity, diet, sleep) and mental health (i.e., depression, anxiety and stress symptoms). The secondary aim was to compare the relative efficacy of a physical activity, dietary behaviour and sleep intervention (Enhanced intervention), with a physical activity and dietary behaviour only intervention (Traditional intervention) on both primary and secondary outcomes. The hypotheses were that the both the Enhanced and the Traditional interventions would achieve greater weight loss than the Control group, and that the Enhanced intervention would achieve greater weight loss than the Traditional intervention.
The primary aim of the current study was to compare the effect of the Pooled Intervention compared to the Control group on the primary outcome of body weight. Body weight did not significantly differ between the Pooled Intervention group compared to the Control at 6 or 12 months, indicating weight loss did not differ between the groups. The Pooled Intervention group reduced energy intake, insomnia symptom severity, and increased resistance training in comparison to the Control group. While body weight did not significantly differ between the two interventions groups, the Traditional group improved waist circumference and sedentary time in comparison to the Enhanced group, and the Enhanced group improved (reduced) the variability in bed time in comparison the Traditional group.
Findings from meta-analyses have shown that e- and m-health weight loss interventions are effective in comparison to control groups [3
]. However, in the current study, body weight did not significantly differ between any of the study groups and this may be due to several potential reasons. Importantly, all groups lost weight relative to baseline including the Control group (Figure 2
a–d). Although weight loss among control group participants is commonly reported in behavioural weight loss interventions [48
], the magnitude of weight loss in the Control group (−1.54 kg at 6 months) in the current study was not anticipated. Potential explanations for this include participants volunteering to participate in a weight loss trial, being allocated to the wait list Control group and engaging in alternative weight loss strategies despite their group allocation. Although no information is available concerning if Control group participants did participate in other weight loss interventions, all participants were asked to not participate in other weight loss interventions during the study.
The physical activity intervention used in this study has been shown to increase resistance training in previous studies [21
], this is consistent with the greater frequency of resistance training in the Pooled Intervention relative to the Control group observed in the current study. Participation in resistance training has important health benefits [4
]. However, it is unclear how the greater frequency of resistance training in the Pooled Intervention influenced the lean muscle mass, body composition and corresponding body weight of these participants and offset any differences in weight loss relative to the Control group. Examining body composition and related outcomes would help to clarify this issue in future studies. Additionally, inclusion criteria did not consider participant lifestyle behaviours, and participants had relatively high levels of moderate-to-vigorous intensity physical activity, and sub-clinical levels of insomnia at baseline [42
]. Consequently, despite modest reductions in energy intake at 6 months, participants may have had limited ability to further improve target behaviours and achieve weight loss over the study period.
With the exception of reduced (i.e., improved) bed time variability in the Enhanced group, no other sleep outcome differed between the two intervention groups. Though insomnia treatments typically focus on reducing wake time variability to help improve sleep drive [50
], reduced bed time variability is part of sleep hygiene recommendations (e.g., have a regular sleep pattern), and is associated with less frequent insufficient sleep [44
]. The reduced bed time variability may reflect changes in participant behaviours to improve sleep in the current study. In trials that included participants with poorer sleep quality and more severe insomnia symptoms than in the current trial, the sleep interventions improved various indicators of sleep health at three and 6 months [21
]. As cognitive and/or behavioural interventions for sleep produce larger improvements when participants have poorer sleep quality at baseline [51
], participants in the current study may have had limited the potential for improvement in sleep quality. Additionally, both intervention groups received the same physical activity intervention and were more likely to meet resistance training guidelines at 6 months than the Control group. As resistance training has been shown to improve sleep quality [52
] this may have attenuated the additional effect of the sleep intervention in the Enhanced group [22
Although the mechanisms are not well established [7
], poor sleep may contribute to weight gain by increased energy intake [12
] and reduced physical activity levels [11
]. Consequently, it was hypothesised that the Enhanced group which included the sleep intervention would produce greater weight loss and improvements in activity and diet behaviours than the Traditional group; this did not occur. Most studies that have examined how sleep influences diet are short term (<5 days) laboratory-based experiments that restrict the sleep duration (<5.5 hrs/d) of people with recommended sleep durations (i.e., 7–9 hrs/d) [12
]. In addition, the previously mentioned study that reported greater weight loss when physical activity, diet and sleep were targeted, compared to physical activity and diet, only examined weight loss over 12 weeks [5
]. By comparison, the current study included participants with mostly sub-clinical levels of insomnia and average sleep durations of 6.5 hrs/d, and aimed to improve sleep over six months in the community setting in the context of a weight loss intervention. These differences may partly explain why the two intervention groups did not differ on weight and energy intake. Moreover, as the dose–response relationship between improved sleep (i.e., dimension of sleep health, magnitude and duration of change) and daily energy intake is unclear, it is possible that the modest improvements in sleep quality and insomnia symptoms over the study period were not sufficient to have any influence on total energy intake.
Self-monitoring behaviours and weight are important determinants of behaviour change and weight loss, respectively [3
]. While there is no consensus on the amount of use and engagement needed to change behaviours, consistent with the current study, most m-health and e-health interventions report that usage declines over time [21
]. The proportion of participants who succumbed to non-usage attrition in the current study (Traditional = 70.7%; Enhanced 84.6%) did not differ between intervention groups and is broadly comparable to other interventions using the Balanced app to target physical activity and sleep combination (68–89%) [21
]. However, direct comparisons between studies are difficult due to differences in self-monitoring methods as the current study used a combination of Fitbit and manual entry, and the previous studies only used manual entry [21
]. As the Enhanced group had a significantly lower number of self-monitoring entries that were manually entered by participants (i.e., steps, resistance training, food, and weight) (Table 4
), it is possible that the self-monitoring requirements in the Enhanced group were too burdensome. This issue combined with the number of different intervention components and delivery modalities used in the intervention (see Table S1
) may have overwhelmed some participants limiting their behavioural changes and subsequent weight loss [58
]. Although efficacy of simultaneous and sequentially delivered interventions does not appear to differ [58
] the self-monitoring differences between groups highlights the importance of carefully targeting and operationalising intervention components in simultaneous multiple behaviour interventions [59
The current study has several strengths. These include the randomised design, the length of the intervention and follow-up relative to many weight loss interventions, and targeting improved sleep health as part of a weight loss intervention [3
]. Limitations, however, include the potential presence of undiagnosed sleep conditions (although the baseline scores on the PSQI and insomnia severity index indicate participants did not have severely impaired sleep). Further, the wrist worn accelerometer is less useful than thigh worn devices for assessing sedentary behaviour, due to the postural component needed to accurately define sedentary behaviour [61
In conclusion, relative to the Control group, the Pooled Intervention group did not differ in terms of body weight, but improved resistance training, and reduced energy intake and insomnia symptom severity. Additional improvements in weight loss, physical activity, diet and sleep behaviours associated with targeting improvements in physical activity, diet and sleep in combination compared to physical activity and diet were not evident. Participants had relatively favourable behavioural profiles at baseline which may have limited the ability of participants to further improve behaviours, and all groups lost weight relative to baseline potentially limiting the ability to detect between-group differences in weight loss.