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Research Updates | Obesity / Overweight

Trends in adult BMI from 1975 to 2014

27 / 07 / 16

NCD Risk Factor Collaboration, "Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled analysis of 1698 population-based measurement studies with 19·2 million participants". The Lancet 387. 10026 (2016): 1377-96.

A large research network of scientists, known as the NCD Risk Factor Collaboration have estimated trends in mean adult body mass index (BMI) in 200 countries from 1975 to 2014.  The team, led by a group from Imperial College London pooled 1698 population based data sources that had measured height and weight of more than 19.2 million adults.

Results showed that in the time period investigated, the mean BMI in men increased from 21.7kg/m2 to 24.2kg/m2 and from 22.1kg/m2 to 24.4 kg/m2 in women. These increases (per decade) are equivalent to the "world's population having become on average more than 1.5kg heavier each decade." The largest increase in men's mean BMI occurred in high-income English speaking countries and in women in central Latin America.

Overall, prevalence of obesity increased from 3.2% to 10.8% in males and 6.4% to 14.9% in women. Conversely, and largely overshadowed by the prevalence of obesity is the fact that over the four decades investigated, global prevalence of underweight decreased from 13.8% to 8.8% in men and from 14.6% to 9.7% in women, with South Asia having the highest prevalence of underweight than any other country.  

It can be expected then that if these trends in obesity prevalence continue the probability of meeting the global obesity target by 2025 is highly unlikely. The authors of the study note that in the lower income countries where accessibility to medical and pharmacological treatment is not as accessible, rising BMI's will have a large effect on population health. Furthermore, underweight and its associated health risks remains a global health problem which requires attention in the form of social and food policies to enhance food security in poorer households. The authors of this study list the following strengths and limitations of the study:

Strengths:

  • The study includes the first-ever estimates of underweight and severe and morbid obesity
  • Great emphasis was placed on data quality and only population based data sources that had measured weight and height were used in order to avoid the bias of self-reported data
  • Data was pooled using a statistical model designed to take into account the epidemiological features of the outcomes such as BMI
  • The model also gave more weight to national data than subnational and community studies

Limitations:

  • Some countries had few data sources especially those in Polynesia and Micronesia, the Caribbean and central Asia
  • Only 42% of sources included people older than 70 years
  • Did not estimate trends in measures of adiposity such as waist circumference and waist to hip ratio