Obesity Crisis Fuelled More By Diet Than Lack Of Physical Activity: Duke University Study

Contrary to the widely held belief that reduced physical activity in increasingly industrialised societies is the primary cause of rising obesity rates, a new global study led by researchers at Duke University’s Pontzer Lab has highlighted dietary changes as the more significant contributing factor.

The study, which analysed health data from over 4,200 adults aged between 18 and 60 years across 34 diverse global populations, suggests that increased calorie consumption, rather than declining energy expenditure, is the principal driver of the global obesity crisis.

The study comes at a time when there is a growing global consensus on the need to curb the consumption of unhealthy foods, limit screen time, and promote outdoor physical activity — particularly among both adults and children — as part of broader efforts to address the escalating obesity crisis.

“Despite decades of public health efforts, there has been considerable uncertainty around whether declining physical activity or dietary habits are more responsible for rising obesity. This large, international collaborative study allows us to test these competing hypotheses. The data clearly point to diet — not reduced activity — as the dominant factor,” said Dr. Herman Pontzer, the lead researcher and professor of evolutionary anthropology at Duke University.

The participants represented a broad spectrum of socioeconomic contexts, ranging from traditional hunter-gatherer and pastoralist communities to urban, industrialised societies. To assess the level of economic development, researchers used the United Nations Human Development Index (HDI), which considers parameters such as life expectancy, education, and income levels.

According to the findings, while there was a slight decline in energy expenditure — adjusted for body size — with increasing levels of industrialisation, these changes were not sufficient to explain the corresponding rise in body fat levels.

“This points strongly to other contributing factors, primarily dietary shifts, as the main cause of increased obesity rates in developed societies,” noted Dr. Amanda McGrosky, lead author of the study and currently an assistant professor of biology at Elon University.

The researchers underscored the importance of refining public health communication and strategies. While they cautioned that the findings should not undermine the role of physical activity, the evidence calls for a renewed focus on dietary interventions.

“Physical activity and diet must be viewed as essential and complementary elements in addressing obesity. They are not interchangeable,” the study emphasised.

The implications of the study are especially concerning in light of the sharp increase in childhood obesity rates. From 1990 to 2022, the prevalence of obesity among children has reportedly quadrupled. This surge brings with it a host of health complications including an elevated risk of liver cirrhosis, cardiovascular diseases, and other chronic conditions.

In India too the situation is not very encouraging as there has been growing national concern over rising obesity rates. According to the India’s National Family Health Survey (NFHS-5), one in every five urban adults in India is either overweight or obese.

A study published with support from The Lancet projects that the number of overweight or obese individuals in India could rise sharply — from 18 crore in 2021 to an estimated 44.9 crore by 2050 — positioning India as the country with the second-highest obesity burden globally.

Also, obesity has been recognised as a key risk factor for a wide spectrum of non-communicable diseases (NCDs), including type 2 diabetes, cardiovascular disease, and certain cancers. It is also increasingly linked to mental health challenges and diminished productivity.

The burden is not limited to affected individuals but extends to families and public healthcare systems as treatment costs for obesity-related diseases is quite high.