New evidence on physical activity and type 2 diabetes 

Research on the impact of physical activity on health outcomes is hampered by its reliance on participants’ self-reporting of their daily exercise, which is subjective. A new study, reported in Diabetes Care, quantifies physical activity with data from a wearable tracker and shows that there is a linear relationship between daily energy expenditure on physical activity and reduced risk of type 2 diabetes, particularly if that activity is more intense. Dr Susan Aldridge reports. 

‘Move more’ has long been part of standard advice for prevention of type 2 diabetes as there is a well-established inverse relationship between physical activity and incidence of the condition. However, most research to date has relied on self-reporting of physical activity, which is subject to bias and difficult to quantify. This makes it hard to be precise in public health messaging when it comes to how much physical activity is needed to make a significant impact on type 2 diabetes incidence. 

The ‘gold standard’ method for measuring physical activity energy expenditure (PAEE) involves the use of calorimetry with radiolabelled water (the ‘stable isotope’ method), which is impractical and expensive for use in large population studies. However, the use of wearables, such as the accelerometers popularised by Fitbits and similar devices, now offers a viable alternative to quantifying dose-response associations of PAEE with health outcomes. 

Few studies have taken this new approach to looking at the impact of PAEE on type 2 diabetes risk. Those that exist have been small and none has validated measurement methods against the gold standard. Accordingly, Søren Brage and Nick Wareham of the Institute of Metabolic Science at Cambridge University have carried out a new study to look at the association between accelerometer-derived PAEE and incident type 2 diabetes in a large cohort of middle-aged adults without diabetes at the start of the study. 

Quantifying daily physical activity

The study population was drawn from the UK Biobank, a prospective health study of over half a million adults recruited between 2006 and 2010. At five years after recruitment, a subsample of 90,096 individuals was invited to wear a wrist accelerometer for a seven-day period. 

Data was summarised according to proportions of daily time spent at different movement intensity levels, from which the researchers calculated PAEE in units of kilojoules per kilogram per day. They also validated their measurements against the stable isotope method in a sub-group of 97 participants. In addition, they worked out the fraction of PAEE from moderate-to-vigorous physical activity (MVPA), as this is an important component when it comes to health outcomes, including type 2 diabetes. Meanwhile, the Hospital Episodes Statistics database, or participant self-report, was used to record incident diabetes up to November 2020. There were 2,018 cases of type 2 diabetes occurring during this time period. 

The researchers also investigated a number of factors that could potentially influence the relationship between PAEE and incident type 2 diabetes. These included sex, age, ethnicity, body mass index (BMI) and genetic predisposition to type 2 diabetes. They also looked at grip strength, cardiovascular fitness, cardiovascular disease and cancer status. This level of detail would allow physical activity advice to be tailored more precisely to the individual. 

Take an extra brisk walk

This was a large, prospective study with objective measurement of PAEE and it revealed a linear inverse relationship between PAEE and the risk of type 2 diabetes, both with and without adjustment for BMI. Furthermore, there was no attenuation in the relationship, even at higher PAEE levels. 

Quantifying PAEE showed that each 5 kJ/kg/day was associated with a 19% lower risk of type 2 diabetes and 11% lower when BMI was adjusted for. This is equivalent to an additional 20-minute brisk walk per day. The findings suggest that the benefits of ‘moving more’ are constant, whatever an individual’s initial level of physical activity. Put simply, ‘some is good, but more is better’. 

The strength of the association between PAEE and type 2 diabetes did differ by sex, BMI and genetic susceptibility to obesity, but the linear inverse relationship persisted among all the subgroups investigated (save for those of non-White ethnicity, where there were too few participants to reach a significant conclusion).

Further analysis showed that intensity of physical activity also had an impact. Accumulating the same PAEE through a higher intensity of exercise was associated with lower risk of type 2 diabetes than accumulating it through a lower intensity activity. This is in line with the authors’ previous research on all-cause mortality and cardiovascular disease. It highlights an important health message – health benefits can be achieved through a variety of combinations of volume and intensity (often put as ‘whatever you enjoy, whatever is sustainable for you’). However, if possible, go for more intense activity, as it delivers more. 

Previous research has shown that higher intensity activities may impact the risk of type 2 diabetes through metabolic adaptations, while lower intensity activities are mediated through changes in BMI. Higher intensity work means greater reliance on carbohydrate oxidation which, in turn, could increase the expression and activity of proteins involved in glucose metabolism and insulin signalling. And perhaps greater stimulation of cardiovascular-related pathways leads to improved cardiovascular fitness which, in itself, lowers the risk of type 2 diabetes. 

So, in summary, there is a strong inverse relationship between accelerometer-derived PAEE and incident type 2 diabetes in a large sample of middle-aged adults. A difference in PAEE equivalent to an extra 20-minute brisk walk per day was associated with 19% lower odds of developing type 2 diabetes. These findings support physical activity for diabetes prevention in the whole population, given that the association persisted across all subgroups, and engaging in more MVPA was associated with additional benefit. 

Therefore, activity intensity, over and above its contribution to PAEE, is particularly important for avoiding incident type 2 diabetes. These new findings add weight to health messaging encouraging physical activity for prevention of type 2 diabetes and should be taken on board by all involved in the prevention agenda.

To read this paper, go to: Strain T, Dempsey PC, Wijndaele K, Sharp SJ, Kerrison N, Gonzales TI, Li C, Wheeler E, Lagenberg C, Brage S, Wareham N. Quantifying the relationship between physical activity energy expenditure and incident type 2 diabetes: a prospective cohort study of device-measured activity in 90,096 adults. Diabetes Care 2023; 46(6):1145–1155. https://doi.org/10.2337/dc22-1467

To learn more, enrol on the EASD e-Learning course ‘Lifestyle intervention’ with ‘Module 2: Promoting physical activity for people with diabetes’ launching soon.

Any opinions expressed in this article are the responsibility of the EASD e-Learning Programme Director, Dr Eleanor D Kennedy.