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About this publication
We carried out a systematic mapping review, commissioned by the Norwegian Directorate of Health. Our aim was to describe available research about interventions to reduce weight in adults with overweight or obesity.
- We included 218 publications (165 studies) published 2010 or later .
- Half of the studies had less than 200 participants
- The participants were mainly adults without overweight and obesity-related
- Nearly half of the studies comprised both changing of diet, increasing physical activity and psychological counselling. Less than 20% comprised only one of them.
- Calorie restriction was the most common element in the interventions (137/165 studies) combined with i) advice on food items (50%), ii) a specific proportion of protein, fat and carbohydrates (25%), iii) calorie restriction alone (25%).
- Interventions for increasing physical activitiy were part of 124 studies, 2/3 of these were training without guidance, 1/3 were with guidance.
- Changes in diet and increased physical activity, with or without psychological counselling, was studied in 115 studies. Advice on calorie restriction in combination with advice on food items together with advice on unorganised physical activity, was part of 47 of these studies.
Lifestyle interventions in the 165 identified studies consists of a large nuber of elements and there is a large variety in how these elements are combined. Future studies on this topic will need to define the elements precisely.
The proportion of adults with overweight and obesity is increasing in the Norwegian population. The propotion with obesity is now 23% for both women and men, according to the Nord-Trøndelag Health Study 2017-18. The main strategies to prevent and treat overweight and obesity in the primary health care services are advice regarding diet and physical activity, and offers of bariatric surgery within the specialist health care services.
The Norwegian Directorate of Health is aware of the need for the treatments available to persons with overweight and obesity in the primary health care services are strengthened. The interventions should be designed to promote changes in diet, physical activity, and psychological councelling including motivation to carry through lifestyle changes and manage health challenges. Even though the primary health care can give weight reducing medication, this is not part of our report.
We carried out a systematic mapping review, commissioned by the Norwegian Directorate of Health. Our aim was to describe available research about interventions (minimum one-year duration) to reduce weight given to adults with overweight or obesity, published 2010 or later.
We searched systematically for literature in the two largest and most relevant electronic databases (Medline and PsychINFO). One author screened all titles and abstracts, and three other authors independently screened about a third each. They then assessed full text publications against inclusion- and exclusion criteria in the same manner. One author extracted data and the three other authors verified the data extraction, about a third each. We did not assess the methodological quality of the included studies. We present the studies in tables with information on who performed the study, which professions that took part, and setting, a description of the participants, the duration and outcomes of the interventions, in addition to the content of the interventions. The content comprises the elements that were part of the studies of change in diet, increased physical activity and psychological counselling to change behaviour and increase motivation to change habits.
From the 17,533 references identified by the search, we included 218 full text publications reporting 165 studies. Half of the studies had less than 200 participants. The participants had overweight or obesity and most of them had no obesity-related or other diseases. Twelve per cent of the studies reported that they included adults with pre-diabetes or diabetes type 2. Half of the studies measured outcomes at the end of the intervention (52%), 36% of the studies at one to two years after the intervention and 12% of the studies more than two years after the intervention.
We categorized the interventions, based on the authors’ descriptions, as follows: interventions to change level of physical activity only; interventions to change level of physical activity and psychological counselling; interventions of change of physical activity and change of diet; interventions to change diet only; interventions to change diet and psychological counselling; interventions to change diet, level of physical activity and psychological counselling; psychological counselling only. Approximately half of the studies (46%) comprised interventions to change diet and level of physical activity, and psychological counselling. In 17% of the studies only one of those mentioned above were included.
In 49% of the studies that reported which professions took part, nutritionists in combination with other professions, e.g. physicians, nurses, psychologists, and physiotherapists, gave the intervention. In 22% of the studies a nutritionist was the only profession mentioned. Even though we know that several professions took part in the study, we do not know how the work was organised.
Calorie restriction was the most common intervention (137/165 studies). Calorie restriction was often combined with i) advice on food items (50%), ii) a specific proportion of protein, fat and carbohydrates (25%), iii) calorie restriction only (25%).
Interventions for increasing physical activities were part of 124 studies, 2/3 of these were training without guidance, 1/3 were with guidance.
A combination of changing of diet and increased physical activity, with or without psychological counselling, was studied in 115 studies. Advice on calorie restriction in combination with advice on food items toghether with advice on unorganised physical activity, was part of 47 of these studies.
The studies identified present a wide array of potential interventions to reduce weight among adults with overweight and obesity. This is an area with extensive research, Howver, because of the very broad question in this review, we had to limit the searches and this led to us losing relevant literature. Even so, this review underscores the variety, volume and complexity of this field of research as per today. This report shows that there are several ways of combining lifestyle interventions, and that the elements that are part of the interventions are many and can be combined in many ways. This presentation of the elements are useful to show the necessity of being precise when defining the research question. This is an important challenge for the future research of overweight and obesity.
Needs for further research
The research question for this review comprised use of weight-reducing medicines and studies from primary care settings. Our search for literature has not identified these studies in an adequate way. Each of these topics should be addressed with narrower and more precise search terms in new systematic reviews.
We have not identified literature on overweight and obesity related diseases adequately. The various overweight and obesity related diseases should also be addressed in separate reviews.
Several of the studies have different phases. There should be a separate project addressing these phases, to identify the importance of the duration of the various phases.
While working on this mapping review we have not had the opportunity to see the interventions in relation to factors that may influence how change in diet and physical activity can be maintained after the intervention (i.e. adherence). It seems necessary to view these two elements together.
We found that lifestyle interventions in the 165 studies identified consists of a large nuber of different elements and that there was a large variety in how these elements were combined. Future studies on this topic will need to define the elements precisely.