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Introduction
Diet
Exercise
Conclusion
References
Introduction
Despite increased public awareness, numerous public health initiatives and the proliferation of organisations offering dietary advice and support, obesity levels in the UK are still rising.1 Currently, around one quarter of adults in the UK are obese, with around two thirds being overweight.2 The prevalence of obesity among older adults in the UK is generally higher than among young people and is thought to reflect a lifetime of weight gain.3 Obesity is associated with significant comorbidities including type 2 diabetes and cardiovascular disease (CVD),4 making it a key public health issue. Importantly, the UK has a very large population of individuals at high risk of developing type 2 diabetes, and the annual conversion rate from this group is 5–10%,5 helping to deliver 700 new cases of diabetes each day.
More worryingly, one in five 11 year olds are now obese, highlighting an emerging problem of childhood obesity. The dramatic increases in the incidence of obesity in children is particularly worrying as it introduces the possibility of lifelong obesity, a public health problem we are yet to really see. The increase in childhood obesity introduces the possibility of comorbidities occurring earlier in life.6 The clearest indication of this is the emergence of type 2 diabetes in the young adult (T2DMY), a form of diabetes that is considered to be more aggressive.7 The prevalence of obesity among those with early onset type 2 diabetes is almost double that of older adults,8 which highlights the dangers of childhood obesity.
Despite significant study, there is still a lack of effective obesity treatment options available. Current diet and exercise regimes are often unsuccessful for the majority,9 and further options are limited as there still exists a paucity of licensed pharmaceutical options available for clinicians to treat obesity, although new weight loss drugs are emerging.10 Beyond this, bariatric surgical procedures are effective in treating obesity and type 2 diabetes,11,12 but due to the risks and costs associated with the surgery are not offered to those with a body mass index (BMI) of less than 40kg/m2 unless a significant comorbidity exists.
There is therefore a significant need to establish novel lifestyle changes that might assist clinicians in dealing with the current and future obesity levels, and the type 2 diabetes cases that are associated. Some potential strategies for weight or glycaemic control are reviewed here.
Diet
It is generally accepted that we eat too much. For most overweight or obese individuals the root cause of their excess adiposity is an imbalance between energy intake and energy expenditure toward energy storage. A recent study in the UK suggested that the average person underestimates their daily calorie intake by around 1000 kcal,13 which provides a sound mechanism for the levels of overweightness and obesity we currently see. Whilst a number of popular diets focus on a single nutrient (for example low fat or low carbohydrate) or support group-based activities, a recent meta-analysis reported that across a population these intervention are broadly similar in efficacy,14 suggesting that individuals may respond to weight loss programmes differently.
There has been considerable focus in recent years on introducing fasting periods into a normal diet for beneficial effect. The most popular form of this intervention, intermittent fasting (IF), has gained mass popularity due to dedicated television programmes and a bestselling diet book. IF is a flexible dietary intervention, which can utilise periods of time within a day to fast (such as the 16:8 diet) or days where calorie intake is either partly or totally restricted (such as the 5:2 diet).
Whilst these interventions have become popular there is still a lack of good randomised controlled trials to accurately measure their efficacy.15,16 Despite this, there are a number of studies that have demonstrated reductions in body weight in the range of 3–8% after 3–24 weeks of treatment17 and from these studies the largest weight loss was seen in interventions where the ‘fast days’ actually delivered some food, such as a meal replacement shake.
Beyond weight loss, fasting diets may be of use in those already diagnosed with type 2 diabetes. One recent study showed that a ‘fasting mimicking diet’ regenerated pancreatic beta-cells and improved glycaemic control in mouse models of both type 1 diabetes and type 2 diabetes.18 Clearly, more high quality clinical trials are needed to establish whether IF is better than general calorie restriction, but it has the potential to be a useful tool in the management of obesity and type 2 diabetes.
Very low calorie diets (VLCDs) may not be new, but they have seen increased attention in recent years due to clarification of how they can improve glycaemic control. VLCDs typically provide 400–800kcal/day of balanced macronutrients supplemented with vitamins, minerals, and trace elements.
A recent systematic review reported that VLCDs in people with type 2 diabetes were associated with significant weight loss, reduction in blood glucose profile and improvement in cardiovascular risk profile, high tolerability and good safety outcomes.19
Several studies have indicated that VLCDs are safe for use by obese diabetic patients.20,21 This form of dietary intervention is associated with rapid weight loss and improvement in glycaemic control and recent studies have suggested that this is due to reductions in lipid storage in the liver and pancreas and that with the appropriate diet structure reversal of type 2 diabetes is possible22 with study participants coming off medication and remaining non-diabetic in follow up. There remain doubts about the long-term efficacy of these diets as weight gain is commonly seen five years after follow up, as with conventional dieting. Clearly, these diets have a powerful effect, but must be undertaken with close medical supervision, especially in those diagnosed with type 2 diabetes.
Exercise
Alongside calorie restriction, exercise is amongst the most powerful tools available to prevent or treat obesity and type 2 diabetes. As a nation, the UK has alarmingly high levels of physical inactivity, with an estimated 20 million adults currently being physically inactive.23 Whilst the benefits of exercise clearly go beyond weight control, meta-analyses have identified that a combined ‘diet and exercise’ approach is the more effective as a weight loss tool than ‘diet’ or exercise alone.24,25
Interestingly, studies have highlighted the importance of resistance training over endurance training in driving weight loss.26,27,28 Current government guidelines for physical activity do include instructions for strength training alongside at least 150 minutes of moderate aerobic activity every week, but it is difficult to assess how many people undertake sufficient resistance training. For type 2 diabetes prevention, resistance training has been shown to be an effective, maintainable strategy for reducing prediabetes prevalence and increasing muscular strength29 and a randomised clinical trial showed that combining resistance training with endurance training induced improvements in HbA1c that were not seen in either resistance training or endurance training alone.30 Resistance training can be particularly important in older adults, with evidence that it can be effective for promoting increases in muscular hypertrophy, strength, and power among untrained older adults31 as well as being an important tool in treating sarcopenia and preventing frailty.32
Physical inactivity is a major modifiable risk factor for obesity and type 2 diabetes, and it is clear that most benefit occurs if people combine resistance training with endurance training and the advice to at risk patients should highlight this.
Recently, newer exercise modalities have been developed and improved that could easily be incorporated into the clinical arsenal of primary care. Often, the perceived barriers to physical activity include time and physical limitations, peer pressure and family responsibilities33 and these barriers can prevent sufficient physical activity from being taken. Introducing exercise forms that can overcome these barriers is therefore essential to promoting physical activity.
One potential form of exercise that eliminates the perceived barrier of time is high-intensity interval training (HIIT). HIIT is a form of exercise alternating short periods of intense anaerobic exercise with less intense recovery periods and is performed in short bursts. HIIT has been shown to be safe if done properly and it can improve blood pressure34 and glycaemic control in older adults with type 2 diabetes,35 as well as being effective in treating depression.36 Support for those undertaking HIIT is a necessity, particularly in older adults, as some form of estimation of physical exertion is needed for people to ensure they are exercising safely, but also at a level that will have a benefit. This can be achieved by using a heart monitor or a rate of perceived exertion scale, such as the Borg scale,37 but care must always be taken to ensure patient safety.
More recently, interesting evidence has emerged to suggest that breaking up exercise into small portions may be an effective way to prevent or manage type 2 diabetes. This so called ‘exercise snacking’ involves multiple bouts of brief periods of exercise and has been shown to control blood glucose levels better than a single, continuous workout.38 This study by Francois et al compared blood glucose in participants who exercised for 30 continuous minutes and also when they divided their exercise up into three small portions performed shortly before their meals. Interestingly, breaking up exercise into smaller portions lowered blood glucose for 24 hours and did so significantly better than a single 30-minute exercise session. Similarly, a separate study showed taking a 10-minute walk after each meal significantly improves glycaemic control in people with type 2 diabetes compared with a single 30-minute walk each day.39
Conclusion
These studies collectively demonstrate that there are new and different ways we can think about how we introduce diet and exercise programmes to overweight or obese individuals, with or without type 2 diabetes. The advice we give to those in need of weight loss needs to reflect these interventions to increase the likelihood of successful adherence and long-term weight management.
J James
M Fotherby
A.K. Mistri
University Hospitals of Leicester NHS Trust
Conflict of interest: none declared
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