You might be interested in…Obesity

Obesity (Part 1)
Overweight and obesity is a major health crisis and a real and present threat to global health progress. In 2021, 3·71 million deaths and 129 million disability-adjusted life-years (DALYs) were attributable to overweight and obesity. In the past two decades, the global age standardised DALY rates associated with overweight and obesity increased by over 15 per cent, placing it as one of the top risk factors for health, and the risk with the steepest increase in attributable burden. Forecasting future trajectories of the obesity epidemic is crucial for providing an evidence base for policy change.

Dr Ray O’Connor

The report of the Global Burden of Disease Collaborators on Obesity was recently published.1 The authors used established methodology from the Global Burden of Diseases, Injuries, and Risk Factors Study, to estimate the prevalence of overweight and obesity among individuals aged 25 years and older, by age and sex for 204 countries and territories from 1990 to 2050.

The findings are stark. Rates of overweight and obesity increased at the global and regional levels, and in all nations, between 1990 and 2021. In 2021, an estimated 1·00 billion adult males and 1·11 billion adult females had overweight and obesity. China had the largest population of adults with overweight and obesity (402 million individuals), followed by India (180 million) and the USA (172 million).

The highest age-standardised prevalence of overweight and obesity was observed in countries in Oceania and north Africa and the Middle East, with many of these countries reporting prevalence of more than 80 per cent in adults. Compared with 1990, the global prevalence of obesity had increased by 155·1 per cent in males and 104·9 per cent in females.

The most rapid rise in obesity prevalence was observed in the north Africa and the Middle East super-region, where age-standardised prevalence rates in males more than tripled, and in females more than doubled. Assuming the continuation of historical trends, by 2050, the authors forecast that the total number of adults living with overweight and obesity will reach 3·80 billion, over half of the likely global adult population at that time.

As if this were not bad enough, another paper from the same study group looks at obesity trends in children and adolescents.2 The authors make the point that despite the well-documented consequences of obesity during childhood and adolescence, and future risks of excess body mass on non-communicable diseases in adulthood, coordinated global action on excess body mass in early life is still insufficient.

Inconsistent measurement and reporting are a barrier to specific targets, resource allocation, and interventions. The findings are that between 1990 and 2021, the combined prevalence of overweight and obesity in children and adolescents doubled, and that of obesity alone tripled. By 2021, 93·1 million individuals aged 5–14 years and 80·6 million aged 15–24 years had obesity.

At the super-region level in 2021, the prevalence of overweight and of obesity was highest in north Africa and the Middle East, and the greatest increase from 1990 to 2021 was seen in southeast Asia, east Asia, and Oceania. By 2021, for females in both age groups, many countries in Australasia and in high-income North America had already transitioned to obesity predominance, as had males and females in a number of countries in north Africa and the Middle East and Oceania.

From 2022 to 2050, global increases in overweight (not obesity) prevalence are forecasted to stabilise. However, the authors conclude that increases in obesity are expected to continue for all populations in all world regions. They recommend that, because substantial change is forecasted to occur between 2022 and 2030, immediate actions are needed to address this public health crisis.

The link between obesity and type 2 diabetes is well-known and documented. I sought to look at some other clinical conditions associated with the condition. One consequence of obesity is the increased risk of certain cancers. General obesity commonly is an established risk factor for colorectal cancer (CRC). However, it is unclear to what extent this association is accounted for by central obesity.

The aim of this study using data from the UK Biobank3 was to evaluate the associations between Body Mass Index (BMI), waist-to-hip ratio (WHR), and waist circumference (WC) with CRC risk and to investigate if and to what extent these associations are independent from each other. Data from more than 500,000 male and female participants aged 40–69, recruited in the UK Biobank study between 2006 and 2010, were analysed.

The findings were that during a median follow-up of 12.5 years 5,977 developed CRC. Multivariable adjusted hazard ratios (HRs) per standard deviation increase of BMI, WHR, and WC were 1.10, 1.18, and 1.14, respectively. WHR showed strong, statistically significant associations with CRC risk within all BMI categories. The authors conclude that central obesity is a much stronger predictor of CRC and may account for most of the CRC risk linked to obesity. They suggest that their findings also emphasize the need for incorporating measures such as WHR alongside BMI in clinical practice to improve obesity prevention and management.

Two-thirds of obesity-related excess mortality is attributable to cardiovascular disease (CVD). Despite the increasingly appreciated link between obesity and a broad range of CVD manifestations including atherosclerotic disease, heart failure, thromboembolic disease, arrhythmias, and sudden cardiac death, the authors of this European Society of Cardiology (ESC) clinical consensus statement4 claim that obesity has been underrecognized and sub-optimally addressed compared with other modifiable cardiovascular risk factors.

In view of major repercussions of the obesity epidemic on public health, attention has focused on population-based and personalized approaches to prevent excess weight gain and maintain a healthy body weight from early childhood and throughout adult life, as well as on comprehensive weight loss interventions for persons with established obesity.

This statement discusses current evidence on the epidemiology and aetiology of obesity; the interplay between obesity, cardiovascular risk factors and cardiac conditions; the clinical management of patients with cardiac disease and obesity; and weight loss strategies including lifestyle changes, interventional procedures, and anti-obesity medications.

Engaging in moderate to vigorous physical activity (MVPA), particularly aerobic activity, is widely acknowledged as a therapeutic strategy for improving cardiometabolic risk factors. It has been postulated that modulating the timing of MVPA may offset diurnal variations in glucose tolerance and insulin sensitivity, potentially leading to durable improvements in cardiovascular morbidity.

The aim of this prospective study5 was to assess the association between timing of aerobic MVPA and risk of CVD, microvascular disease (MVD), and all-cause mortality in adults with obesity and a subset with obesity and type 2 diabetes (T2D).

The core sample included 29,836 adults with obesity, with a mean age of 62.2 years. Over a mean follow-up period of 7.9 years, 1,425 deaths, 3,980 CVD events, and 2,162 MVD events occurred. Compared with activity in the reference group, evening MVPA was associated with the lowest risk of mortality (HR 0.39), whereas afternoon (HR 0.60) and morning MVPA (HR 0.67) demonstrated significant but weaker associations. Similar patterns were observed for CVD and MVD incidence. The authors recommend that timing of physical activity may play a role in the future of obesity and T2D management.

References:

1. GBD 2021 Adult Global BMI Collaborators. Global, regional, and national prevalence of adult overweight and obesity, 1990–2021, with forecasts to 2050: a forecasting study for the Global Burden of Disease Study 2021. Lancet 2025; 405: 813–38 Published Online March 3, 2025. https://doi.org/10.1016/S0140-6736(25)00355-1
2. GBD 2021 Adolescent BMI Collaborators. Global, regional, and national prevalence of child and adolescent overweight and obesity, 1990–2021, with forecasts to 2050: a forecasting study for the Global Burden of Disease Study 2021. Lancet 2025; 405: 785–812 Published Online March 3, 2025. https://doi.org/10.1016/S0140-6736(25)00397-6
3. Safizadeh F et al. Central obesity may account for most of the colorectal cancer risk linked to obesity: evidence from the UK Biobank prospective cohort. International Journal of Obesity; https://doi.org/10.1038/s41366-024-01680-7
4. Koskinas K et al. Obesity and cardiovascular disease: an ESC clinical consensus statement. Eur Heart J 2024 Oct 7;45(38):4063-4098. doi: 10.1093/eurheartj/ehae508
5. Sabag A et al. Timing of Moderate to Vigorous Physical Activity, Mortality, Cardiovascular Disease, and Microvascular Disease in Adults With Obesity. Diabetes Care 2024;47:890–897  https://doi.org/10.2337/dc23-2448