This blog has been reproduced in full from Evidently Cochrane. To read more Evidently Cochrane blogs, click here.

Let’s get a couple of things straight at the start. We don’t know what causes type 1 diabetes or how to prevent it. We do know that type 2 diabetes is largely preventable. We’re too fat, too sedentary and too many of us now have type 2 diabetes. Now for a bit of detail.

The first World Health Organization (WHO) Global report on diabetes, published this week ahead of World Health Day, makes no bones about the scale of the problem (422 million adults living with diabetes, four times as many as in 1980) or that the skyrocketing numbers of people who are overweight or obese is a significant factor behind this alarming increase, much of it in developing countries. The report reminds us that type 2 diabetes “comprises the majority of people with diabetes around the world, and is largely the result of excess body weight and physical inactivity”. Increasingly, this includes children.

The WHO report highlights the need to address gaps in the diabetes knowledge base. Systematic reviews are a great way to bring together the best available evidence from primary research so we can see what is known to help us make decisions about health and where important gaps remain.

Physical activity and a healthy diet are important for preventing type 2 diabetes

WHO advice on preventing type 2 diabetes

The WHO says that “simple lifestyle measures have been shown to be effective in preventing or delaying the onset of type 2 diabetes. To help prevent type 2 diabetes and its complications, people should:

• achieve and maintain healthy body weight;
• be physically active – at least 30 minutes of regular, moderate-intensity activity on most days. More activity is required for weight control;
• eat a healthy diet, avoiding sugar and saturated fats intake; and
• avoid tobacco use – smoking increases the risk of diabetes and cardiovascular diseases.”

Diet and exercise: better than drugs

The WHO report draws on a Cochrane review on the effects of exercise or diet and exercise for preventing type 2 diabetes, with evidence that “interventions that promote healthy diet, physical activity and weight loss can prevent type 2 diabetes in people at high risk”. The high risk groups include people who are overweight or obese. Citing this review and a more recent, non-Cochrane systematic review (Merlotti, 2014), WHO states that

“Several pharmacological interventions (for example, metformin and acarbose) have also been shown to prevent or delay type 2 diabetes but, in the majority of studies, this is not as effective as changes in diet and physical activity, and the effect dissipates after discontinuation of the medication.”

Evidence shows we all eat more when offered larger portions, packages or tableware

Watch your portion size!

If you missed our blog on recent Cochrane evidence on the impact of portion size on how much we all eat and drink, now is a good time to catch up with it. Along with the blog, you can find our blogshots, infographic and an excellent animation explaining the review here.

Promoting healthy weight in children

Approaches to preventing overweight/obesity

A Cochrane review on interventions for preventing obesity in children found strong evidence to support the beneficial effects of child obesity prevention programmes on body mass index, particularly for programmes targeting children aged six to twelve. The review includes a meta-analysis of 37 studies with almost 28,000 children. Disappointingly, the evidence doesn’t tell us which components of the programmes contributed most to the beneficial effects seen, but promising policies and strategies include school-based approaches to improving diet and physical activity and parent support and home-based activities that encourage children to be more active, eat more nutritious foods and spend less time in screen-based activities. You can hear lead author Elizabeth Waters talking about the review in this podcast.

Approaches to treating overweight/obesity

Multicomponent interventions may be effective for reducing overweight and obesity in children

A new Cochrane review, published last month, brought together the best available evidence on different approaches to treating overweight and obesity in children up to age six, through dietary interventions or multicomponent interventions which included behavioural, dietary and physical activity components. The reviewers conclude that multicomponent interventions may be effective for reducing body mass index and weight in overweight or obese children. Other effects (good and bad) are unclear and the role of dietary interventions remains uncertain. As so often, the review highlights that much research is wasted because of shortcomings in the way studies are designed and reported. We need more, high quality, research to tell us which strategies are effective.

An earlier review found 64 studies with over 5000 children, evaluating lifestyle or drug interventions for treating obesity. Whilst there was not enough good evidence to say which intervention is more effective than another, the reviewers found that:

“combined dietary, physical activity and behavioural component appears effective. Evidence from this review shows that family-based, lifestyle interventions with a behavioural program aimed at changing diet and physical activity thinking patterns provide significant and clinically meaningful decrease in overweight in both children and adolescents compared to standard care or self-help in the short- and the long-term.”

The addition of drug treatment to a lifestyle programme for moderate to severely overweight adolescents was found to enhance weight loss but a range of adverse effects were seen.

Another Cochrane review found that diet, physical activity and behavioural interventions delivered to only the parents of overweight or obese 5 to 11 year olds may be an effective treatment option, and had similar effects to those delivered to parents and their children. The evidence is limited, but the reviewers identified ten ongoing trials which they hope will contribute to future updates of the review.

I’ll leave the last word to the WHO, from their new report:

Key messages from WHO on preventing diabetes

• Type 2 diabetes is largely preventable
• Multisectoral, population-based approaches are needed to reduce the prevalence of modifiable diabetes risk factors – such as   overweight, obesity, physical inactivity and unhealthy diet – in the general population
• A combination of fiscal policies, legislation, changes to the environment and raising awareness of health risks works best for promoting healthier diets and physical activity
• Diabetes can be delayed or prevented in people who are overweight and have impaired glucose tolerance (IGT). Diet and physical activity interventions are more effective than medication

Preventing diabetes: eating, exercise and evidence by Sarah Chapman is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.
Based on a work at http://www.cochranelibrary.com. Photographic mages have been purchased for Evidently Cochrane from shutterstock.com and may not be reproduced.

Links:

World Health Organization. “World Health Day 2016: WHO calls for global action to halt rise in and improve care for people with diabetes”. [Press release]. World Health Organization, Media Centre, 6 April 2016. Web. 7 April 2016.http://www.who.int/mediacentre/news/releases/2016/world-health-day/en/

World Health Organization. Global Report on Diabetes. Geneva: World Health Organization; 2016. Available from:http://www.who.int/diabetes/global-report/en/

Orozco LJ, Buchleitner AM, Gimenez-Perez G, Roqué i Figuls M, Richter B, Mauricio D. Exercise or exercise and diet for preventing type 2 diabetes mellitus. Cochrane Database of Systematic Reviews 2008, Issue 3. Art. No.: CD003054. DOI:10.1002/14651858.CD003054.pub3

Merlotti C, Morabito A, Pontiroli AE. Prevention of type 2 diabetes; a systematic review and meta- analysis of different intervention strategies. Diabetes, Obesity and Metabolism. 2014;16:(8)719–727. http://www.ncbi.nlm.nih.gov/pubmed/24476122

Chapman S. “Let’s talk about portion size and overeating”. Evidently Cochrane. 15 September 2015. Web. 07 April 2016. http://www.evidentlycochrane.net/lets-talk-about-portion-size-and-overeating/

Waters E, de Silva-Sanigorski A, Burford BJ, Brown T, Campbell KJ, Gao Y, Armstrong R, Prosser L, Summerbell CD. Interventions for preventing obesity in children. Cochrane Database of Systematic Reviews 2011, Issue 12. Art. No.: CD001871. DOI: 10.1002/14651858.CD001871.pub3.

Podcast of this review: https://www.cochrane.org/podcasts/10.1002/14651858.CD001871.pub3

Colquitt JL, Loveman E, O’Malley C, Azevedo LB, Mead E, Al-Khudairy L, Ells LJ, Metzendorf MI, Rees K. Diet, physical activity, and behavioural interventions for the treatment of overweight or obesity in preschool children up to the age of 6 years. Cochrane Database of Systematic Reviews 2016, Issue 3. Art. No.: CD012105. DOI: 10.1002/14651858.CD012105.

World Health Organization. “Global Strategy on Diet, Physical Activity and Health”. [online resource]. World Health Organization, Programmes. Web. 07 April 2016. http://www.who.int/dietphysicalactivity/en/