Evidence based interventions
There are multiple ways of looking at this topic.
What are the guidelines and recommendations?
What is the evidence behind the recommendations?
- Prevention of the development of physical inactivity and obesity
- The benefits of intervention on increasing physical activity and reducing obesity
- Further extension to any subsequent health effects of the interventions
Despite the acknowledgement of the health risks physical inactivity and obesity, evidence of the most appropriate interventions and of the benefits is small – as are the effects of most interventions!
Because so many of the interventions discuss both diet and physical activity, we will present them together.
First – the recommendations
In 2014 (later confirmed), WHO released its Noncommunicable Diseases Global Monitoring Framework: Indicator Definitions and Specifications (pdf) This included the following targets and indicators:
Target: At least 10% relative reduction in prevalence of insufficient physical activity
Indicators: Prevalence of insufficiently physically active adolescents, defined as less than 60 minutes of moderate to vigorous intensity activity daily
Age-standardised prevalence of insufficiently physically active persons aged 18+ years (defined as less than 150 minutes of moderate-intensity activity per week, or equivalent).
Target: Halt the rise in diabetes & obesity
Indicators: Prevalence of overweight and obesity in adolescents (defined according to the WHO growth reference for schoolaged children and adolescents, overweight – one standard deviation body mass index for age and sex, and obese – two standard deviations body mass index for age and sex)
Age-standardized prevalence of overweight and obesity in persons aged 18+ years (defined as body mass index 25kg/m² for overweight and body mass index 30 kg/m² for obesity)
This was updated in 2018 with a more detailed Global action plan on physical activity 2018–2030: more active people for a healthier world
Target: A 15% relative reduction in the global prevalence of physical inactivity in adults and in adolescents by 2030 (relative to 2016).
Four strategic objectives provide a universally applicable framework for the 20 multidimensional policy actions, each identified as an important and effective component of a population-based response to increasing physical activity and reducing sedentary behaviour. In combination, they capture the whole-of-system approach required to create a society that intrinsically values and prioritizes policy investments in physical activity as a regular part of everyday life.
The four strategic objectives are:
1. Create an active society – social norms and attitudes:
Create a paradigm shift in all of society by enhancing knowledge and understanding of, and appreciation for, the multiple benefits of regular physical activity, according to ability and at all ages.
2. Create active environments – spaces and places: Create and maintain environments that promote and safeguard the rights of all people, of all ages, to have equitable access to safe places and spaces, in their cities and communities, in which to engage in regular physical activity, according to ability.
3. Create active people – programmes and opportunities: Create and promote access to opportunities and programmes, across multiple settings, to help people of all ages and abilities to engage in regular physical activity as individuals, families and communities
4. Create active systems – governance and policy enablers: Create and strengthen leadership, governance, multisectoral partnerships, workforce capabilities, advocacy and information systems across sectors, to achieve excellence in resource mobilization and implementation of coordinated international, national and subnational action to increase physical activity and reduce sedentary behaviour.
The WHO in its Obesity and overweight factsheet has a section:
How can overweight and obesity be reduced?
Overweight and obesity, as well as their related noncommunicable diseases, are largely preventable. Supportive environments and communities are fundamental in shaping people’s choices, by making the choice of healthier foods and regular physical activity the easiest choice (the choice that is the most accessible, available and affordable), and therefore preventing overweight and obesity.
At the individual level, people can:
- limit energy intake from total fats and sugars;
- increase consumption of fruit and vegetables, as well as legumes, whole grains and nuts; and
- engage in regular physical activity (60 minutes a day for children and 150 minutes spread through the week for adults).
Individual responsibility can only have its full effect where people have access to a healthy lifestyle. Therefore, at the societal level it is important to support individuals in following the recommendations above, through sustained implementation of evidence based and population based policies that make regular physical activity and healthier dietary choices available, affordable and easily accessible to everyone, particularly to the poorest individuals. An example of such a policy is a tax on sugar sweetened beverages.
The food industry can play a significant role in promoting healthy diets by:
- reducing the fat, sugar and salt content of processed foods;
- ensuring that healthy and nutritious choices are available and affordable to all consumers;
- restricting marketing of foods high in sugars, salt and fats, especially those foods aimed at children and teenagers; and
- ensuring the availability of healthy food choices and supporting regular physical activity practice in the workplace.
You can find details of a national approach for physical activity in the UK, through UK Motivate 2 Move module “to give all health care professions, the background information to educate and motivate patients about the health benefits of physical activity.” They summarise the approach:
“Regular physical activity provides a range of physical and mental health benefits. These include reducing the risk of disease, managing existing conditions, and developing and maintaining physical and mental function. It also contributes to a range of wider social benefits for individuals and communities, which include: improved learning and attainment, managing stress, self-efficacy, improved sleep, the development of social skills, and better social interaction.”
There are many other national guidelines, but most have similar recommendations.
You might also like to explore information from the advocacy group Exercise Works! which has many links and offers a curriculum on exercise for medical students.
While all of these initiatives are to some extent evidence based, they mainly rely on the evidence relating to risk - the evidence base of successful interventions is weak.
Preventing obesity and physical inactivity
Interventions aimed at preventing and reducing overweight/obesity among children and adolescents: a meta‐synthesis suggests: "Overall, the results of this meta‐synthesis suggest that interventions result in statistically significant effects albeit of relatively little clinical relevance."
Interventions to prevent global childhood overweight and obesity: a system is more positive: "The effectiveness of school-based interventions that combined diet and phyiscal activity components suggests that they hold promise for childhood prevention worldwide."
Interventions to Prevent Obesity: A Systematic Review says: "...the evidence shows that school-based interventions can reduce weight gain and the development of obesity in children and adolescents (strong scientific evidence). The fact that two thirds of the studies fail to demonstrate a positive effect may reflect the difficulty of achieving lifestyle changes in children and adolescents with school-based interventions alone that do not include the home environment, free time, and the community at large.
Based on all of the studies involving adults, obesity can be prevented by interventions that improve diet and physical activity (moderately strong scientific evidence).The lack of effects in nearly half of the studies may be explained by the difficulty in achieving lifestyle changes, that the interventions have been too limited or they were limited to recommendations focusing only on increased physical activity."
The Cochrane review Community wide interventions for increasing physical activity concludes: "Although numerous studies have been undertaken, there is a noticeable inconsistency of the findings in the available studies and this is confounded by serious methodological issues within the included studies. The body of evidence in this review does not support the hypothesis that the multi‐component community wide interventions studied effectively increased physical activity for the population, although some studies with environmental components observed more people walking."
Physical Activity: Health Impact, Prevalence, Correlates and Interventions finds: "Regular PA is an effective primary and secondary preventative strategy against at least 25 chronic medical conditions with risk reduction typically in the 20-30% range. While approximately 75% of adults meet recommended PA guidelines, the prevalence is slightly lower for women compared to men, and considerably lower for youth, older adults and those in higher income countries. Motivation, self-efficacy and self-regulation remain consistent correlates of PA. Interventions show PA changes in the small effect size range for adults and youth but the heterogeneity is considerable across studies. Only a few (aggregate of behavioural regulation strategies, supervision, high frequency of contact) reliable moderators of intervention success were identified across study quality, sample characteristics, theory/behaviour change techniques and delivery modes/settings."
Reducing levels of obesity and increasing physical activity
An important review shows that while exercise can be useful in achieving weight loss, the gains are small.
Physical activity and obesity: what we know and what we need to know “Our critical review of the literature, after eliminating studies that were ill‐equipped to answer the question at hand, indicated that diet + exercise combined interventions were more effective than diet‐only interventions in inducing Weight Loss (WL) at 6 months. Such interventions typically result in 8–11% WL. Notably, however, moderate‐intensity to high‐intensity Aerobic Exercise (AE)‐only interventions without prescribed diet, conducted at a frequency of at least three to five times per week, were also effective in giving rise to approximately 2–3% loss of the initial weight within 6 months. In addition, interventions that target low‐intensity walking and habitual activity that typically targets increasing daily ‘step counts’ also appear to produce modest WLs of 1–1.5% of the initial weight at 3–6 months. Conversely, Resistance Training (RT) alone does not appear to be effective in inducing WL
Weight loss programmes vary considerably in how they present their recommendations. However, in our experience, a frequently recommended approach (particularly in public health domains) is to target increases in physical activity that focus only on increasing daily steps to 10,000. Our review suggests that this strategy may not be optimal. In fact, taken together, our findings suggest that recommendations for physical activity to achieve WL should target each of moderate‐intensity AE and RT in planned prescribed exercise sessions coupled with recommendations to target 10,000 steps in addition to structured exercise for maximum benefit as this form of activity appears to contribute independently to WL.”
When is comes to maintaining any achieved weight loss, the authors state: “Strong evidence for the value of exercise in maintaining lost weight is sparse, and frequent assertions that exercise is more important for maintenance than initial WL appear not to be supported by our findings.”
Are physical activity interventions for healthy inactive adults effective in promoting behavior change and maintenance, and which behavior change techniques are effective? A systematic review and meta-analysis finds: "Physical activity interventions were effective at changing behavior and maintaining behavior change after 6 months or more. Sedentary behavior interventions were not effective."
Another Cochrane review Diet, physical activity and behavioural interventions for the treatment of overweight or obese children from the age of 6 to 11 years concludes: "Multi-component behaviour-changing interventions that incorporate diet, physical activity and behaviour change may be beneficial in achieving small, short-term reductions in BMI, BMI z score and weight in children aged 6 to 11 years. The evidence suggests a very low occurrence of adverse events. The quality of the evidence was low or very low."
The setting: Individual, primary care or population approaches?
How Can Physical Activity Be Promoted Among Children and Adolescents? A Systematic Review of Reviews Across Settings "The review of reviews identified a number of promising strategies for PA promotion among children and adolescents. Among reviews, multi-component interventions in childcare facilities and schools stand out prominently. At the same time, the review of reviews indicated that there is still a lack of studies on the efficacy of interventions that go beyond the individual level. We recommend that future research should also target community and policy level interventions and interventions other than the school setting. In order to make more specific recommendations regarding the scale-up of promising intervention strategies, further knowledge about the effectiveness, health equity and cost effectiveness of interventions is needed."
Are brief interventions to increase physical activity cost-effective? A systematic review "Brief interventions promoting physical activity in primary care and the community are likely to be inexpensive compared with usual care. Given the commonly accepted thresholds, they appear to be cost-effective on the whole, although there is notable variation between studies."
A 2019 paper Diet and physical activity interventions targeting children and youth have different, yet small, effects on preventing obesity concludes: "Obesity prevention interventions which include both diet and physical activity may reduce the risk of obesity in pre-school children. Once at school, physical activity appears to be more effective for weight loss than diet alone. Resulting weight loss form any intervention, if any, has been very small with unclear benefits to the individual or population."
A published commentary on the paper says: "Despite an increase in the number of trials included in this review, the evidence is still scant. While individual-level interventions may show small impact they appear short-lived and of limited clinical significance.
Policymakers may take the view that some evidence is better than no evidence and continue to pursue diet and physical activity interventions, as part of a whole system approach, safe that they will not increase health inequalities. Others will take the view that population-level approaches including improved food formulation and creating active environments, may have larger impacts despite the lack of randomised trial evidence."
Another, different population approach is described here:
Built environment for physical activity—An urban barometer, surveillance, and monitoring "Holding individuals responsible for obesity detracts from the obesogenic built environments. Pedestrian priority and dignity, wide pavements with tree canopies, water fountains with potable water, benches for the elderly at regular intervals, access to open‐green spaces within 0.5‐km radius and playgrounds in schools are required. Facilities for physical activity at worksite, prioritization of staircases and ramps in building construction, redistribution of land use, and access to quality, adequate capacity, comfortable, and well‐networked public transport, which are elderly and differently abled sensitive with universal design are some of the interventions that require urgent implementation and monitoring.
Bold actions towards protecting and creating health and environment‐sensitive built environments with dynamic urban barometers for monitoring and surveillance is the need of the hour."
Health effects of weight loss and increasing physical activity
It is much easier to show the risk of health outcomes of obesity or physical inactivity than to demonstrate reversal after an intervention, but here are a few examples from systematic reviews:
Behavioral and Pharmacotherapy Weight Loss Interventions to Prevent Obesity-Related Morbidity and Mortality in Adults: An Updated Systematic Review for the U.S. Preventive Services Task Force "We found that behavior-based weight-loss interventions with or without weight loss medications resulted in more weight loss than usual care conditions....we noted that weight loss interventions resulted in a decreased risk of developing diabetes, particularly among those with prediabetes, although the prevalence of other intermediate health outcomes was less well reported. Limited evidence exists regarding health outcomes associated with weight loss interventions. Weight loss medications, but not behavior-based interventions, were associated with higher rates of harms compared with control arms."
Behavioral Counseling to Promote a Healthful Diet and Physical Activity for Cardiovascular Disease Prevention in Adults Without Known Cardiovascular Disease Risk Factors: Updated Systematic Review for the U.S. Preventive Services Task Force "In general, diet and physical activity behavioral interventions for generally unselected adults who were not targeted for counseling based on their CVD risk resulted in consistent modest benefits across a variety of important intermediate health outcomes, including blood pressure, low-density lipoprotein, and total cholesterol levels as well as adiposity, with evidence of a dose-response effect with higher intensity interventions resulting in greater improvements. Small-to-moderate improvements were also seen in dietary and physical activity behaviors. Very limited evidence exists on health outcomes or harmful effects of these interventions. The improvements we saw, however, in intermediate and behavioral health outcomes could translate into long-term reduction in CVD-related events, with minimal to no harms, if such changes were maintained over time."
There is evidence for beneficial effects of physical activity on mental health:
Health benefits, safety and cost of physical activity interventions for mental health conditions: A meta-review to inform translation efforts "33 reviews (including 155 unique studies) were included and 32 reported that PA has a positive effect on at least one main outcome of interest (symptoms of mental illness, quality of life and/or physical health)."
Although not published as a research paper, How physical exercise makes your brain work better reviews the evidence and concludes: "A wave of studies exploring the unexpected links between mental and bodily fitness is emerging..."
There is a great deal of evidence of the harmful effects of obesity and physical inactivity on health. There is some evidence that interventions may help in the prevention and management of both conditions, but the impact is small. There is little research to provide evidence of population level interventions, or of the health benefits of interventions. There are, however, a number of guidelines that encourage interventions. The best summary of what to do might be from the commentary to one of the reviews listed above:
"Policymakers may take the view that some evidence is better than no evidence and continue to pursue diet and physical activity interventions."