Key Question: Is the government right to prescribe cycling to tackle obesity?
Recently you have probably seen articles about the government’s idea to prescribe cycling as part of a 12-week plan to counteract obesity... sometimes accompanied by a (rather funny) picture of Boris Johnson riding a bike. If not, you can click here for the BBC’s full article. The article outlines that the UK has a population where many people can be classified as obese, hints that having obesity causes an increased risk of COVID-19, and states the following:
1) GPs will be encouraged to prescribe cycling in pilot areas identified as having poor health outcomes.
2) Surgeries will provide access to bikes and…local cycling infrastructure will be improved.
3) This may include segregated cycle lanes, low traffic neighbourhoods and secure cycle parking.
However, there are some flaws. Firstly does having obesity cause an increased risk of severe complications with COVID-19? It is not clear cut. Instead it could be another common trait that people classified as obese are likely to have, such as a low fitness level, which contributes to the increased risk. That is not the main point of today’s article but it can be frustrating to see science reported with such simplicity.
The Good?
Let's get something clear. Encouraging more exercise is a wonderful initiative. Exercise is often described as being a medicine, and can help to reduce the risk of a huge number of diseases (for a review covering 26 of those you can click here) and can also have benefits for psychological well-being. It is also well publicised that the UK’s population do not exercise enough and are often highly sedentary and these behaviours also increase the risk of many diseases. Public Health England produce reports based on population studies and these suggest close to 50 % of the UK population is not active enough for good health. Behaviour change is not easy and requires (among other factors), opportunities and the environment to be able to perform the chosen behaviour, social-support and self-regulation. So is the news that the government will spend more money on helping people to increase their physical activity levels with support and in a safe environment a good thing? Yes!
The Bad?
However, will 12 weeks of cycling solve the obesity problem? Probably (almost definitely) not! For most people exercise will create a relatively small calorie deficit. Resting conditions have a metabolic equivalent (MET) score of 1, so we can compare other physical activities to this score. For example, an activity with a MET score of 3 means you would be burning three times as much energy as rest. To work out energy expenditure in calories for an activity you can use an equation: MET x your body weight in kg x the duration in hours. You can click here for a list of MET scores. Cycling for leisure gets a MET score of ~5, depending on the speed. If someone weighs 100 kg and cycled for 1 hour this would be an energy expenditure of (5 x 100 x 1) = 500 kcal. If they cycled for three hours a week (exceeding the government guidelines of 150 minutes of exercise) this would mean a weekly expenditure of 1500 kcal. This is a small amount of energy as we consume around 1 MILLION calories every year, and the 500 kcal from the bike ride could be eroded by a snack or a decrease in non-exercise activity, including activity (e.g. gardening) you might be doing instead of exercising.
Indeed, a review published in 2018, concluded that people 'seeking to lose weight without changing their dietary habits need to be counselled that high PA levels (225–420 min/week of exercise) are necessary to achieve clinically significant weight loss '. There have been many studies showing that exercise interventions for a short period of time (e.g. 12 weeks) will produce a very modest weight loss and sometimes no weight loss. That does not mean that people don’t get healthier or reduce the risk of diseases with exercise, but for obesity, doing a relatively modest amount of exercise might not be the solution. Another big problem is that people often have unrealistic expectations regarding exercise and weight loss, and fail to achieve these goals. Their confidence in their ability to achieve weight loss and their motivation can then be reduced, which increases the likelihood of giving up. This is where inaccurate messages in the media can end up doing more harm than good.
The Really Bad?
When it comes to obesity, the messaging in the media leaves a lot to be desired. Obesity is a complex disease state, which develops due to an array of interlinking environmental, genetic, social and hormonal factors. However, unlike many other diseases (e.g. cancer), obesity is associated with a stigma or shame factor. Obesity is not simply a failure of willpower and in the last decade an ever increasing number of barriers to physical activity and healthy eating have developed. These include changes in our work patterns (desk jobs), the availability and marketing of food, the layout of supermarkets to name a few. The most disadvantaged people also face the most barriers, for example in having the time and money to exercise and the access to healthy food. We are not talking about a lack of willpower and should not portray obesity as a failure. It’s a complex disease and needs a coordinated, well-structured and multi-layer approach that considers exercise and diet. Organisations like Public Health England do great work and you can read more here.
After the article on the BBC on the 26th July regarding cycling for weight loss, I woke up this morning to another article about reducing 'buy one get one free deals' in supermarkets to target certain highly-processed foods. In my opinion this is a step in the right direction. This review article highlights the benefits of diet and combined diet and exercise interventions for weight loss compared to exercise alone if you want to read more about that.
The take-home message: Encouraging exercise is a great initiative. However prescribing cycling for weight loss may not be the most successful approach and we need to remember that obesity is a complex disease state (not simply a lack of willpower), and requires a comprehensive strategy that targets both diet and exercise. Don't forgot to sign up for the blog (click here) and follow us on Instagram (click here).