by Lancet

Credit: Unsplash/CC0 Public Domain

Over the past three decades, there has been a startling increase in the prevalence of obesity across the U.S., at least doubling in adult men and women (aged 25 and older) and older female and male adolescents (aged 15–24 years) since 1990, with the number of people living with overweight and obesity reaching over 208 million in 2021—a trend set to continue in the coming decades without significant reform, according to a major new analysis from the Global Burden of Disease Study Collaborator Network, published in The Lancet.

Especially high levels of overweight and obesity have already been reached in several US states, with over half (52%) of older adolescent males (aged 15–24 years) in Texas and nearly two-thirds (63%) of older adolescent females in Mississippi living with overweight or obesity in 2021. Similarly, in adults (aged 25 or older), around 80% of men in North Dakota and women in Mississippi were estimated to have overweight or obesity in 2021.

The study predicts devastating trends at the population level. The total number of US children and adolescents with overweight and obesity is expected to reach 43.1 million by 2050 (an additional 6.74 million from 2021), and the number of adults 213 million (an additional 41.4 million), underscoring the urgent need for concerted population-wide action to reverse these trends and the stark geographical and sex disparities.

"Our analysis lays bare the decades-long failure to tackle the growing overweight and obesity epidemic in the U.S. The catastrophic consequences of the surge in overweight and obesity among children are already evident in the rising prevalence of childhood hypertension and type 2 diabetes," said lead author Professor Emmanuela Gakidou from the Institute for Health Metrics and Evaluation (IHME), University of Washington, U.S.

"Overweight and obesity can trigger serious health conditions—many of which are now occurring at younger ages, including diabetes, heart attacks, stroke, cancer, mental health disorders, and even premature death.

"The soaring health system and economic costs will be equally pervasive, with over 260 million people in the U.S., including over half of all children and adolescents, expected to be living with overweight or obesity by 2050. United efforts and urgent investments are needed to alter these troubling trajectories and ensure a healthier future for current and upcoming generations."

The new analysis estimated the prevalence of overweight and obesity for children and young adolescents (aged 5–14 years), older adolescents (aged 15–24 years), and adults (aged 25 and older) from 1990 to 2021 with forecasts to 2050 (assuming continuation of past trends and patterns) using 134 unique data sources, including all major national surveillance survey data.

The new analysis provides in-depth forecasts, broken down at the state level, as well as by age and sex. Adjustments were made to correct for self-reporting bias.

For individuals older than 18 years, overweight was defined as having a BMI of 25 kg/m² to less than 30 kg/m² and obesity was defined as a BMI of 30 kg/m² or higher. For individuals younger than 18 years, definitions were based on International Obesity Task Force criteria.

213 million American adults predicted to have overweight or obesity in 2050

Almost three-quarters of the adult population (172 million adults aged 25 or older) in the U.S. were estimated to be living with overweight or obesity in 2021. The prevalence of obesity rose especially rapidly, doubling between 1990 and 2021 in both adult men (from 18.6% to 41.5%) and women (from 22.8% to 45.6%).

The estimated prevalence of adult overweight and obesity was high across all states in 2021. In men, levels ranged from 80.6% in North Dakota to 65.3% in Washington DC; while in women, levels ranged from 79.9% in Mississippi to 63.7% in Hawaii.

Continuation of these trends would see overweight and obesity prevalence among adults (age-standardized to allow comparisons between states and over time) rise from an estimated 75.9% in 2021 to around 81.1% for men and from 72.6% to 82.1% for women. This would mean an estimated 41.4 million additional adults living with overweight or obesity by 2050 (raising the total to 213 million, of whom 146 million will have obesity).

Concerningly, the prevalence of obesity is projected to increase at a more rapid rate than overweight, and faster among adult men than women. Between 2021 and 2050, the highest rise in obesity prevalence among men is expected in Colorado (up 44.2%) and New Mexico (up 41.2%), and among adult women in Kansas and Colorado (both up 34.9%).

However, the highest levels of obesity are expected to remain in the southern states, with around two-thirds of adult men in West Virginia and Kentucky forecast to be living with obesity by 2050, as well as two-thirds of adult women in 12 states, with especially high rates of obesity predicted in Mississippi, West Virginia, and Arkansas and Alabama (both around 69%).

Interestingly, the onset of obesity has become earlier over subsequent generations. For example, approximately two out of five women born in the 1960s were living with obesity at the age of 45, however the same proportion were living with obesity by the age of 30 for women born in the 1980s, and by the age of 20 for women born in 2000.

"Obesity is at a crisis point throughout the U.S., with every state challenged to some degree," said co-author Affiliate Associate Professor Marie Ng from IHME, University of Washington, U.S.

"Over the past three decades, the country has experienced extensive economic, demographic, and technological transitions that have triggered profound changes to food and agricultural systems, urbanization, and wealth and educational inequalities together with underlying structural racism that all interact to drive population-wide obesity—whether it be the marketing of unhealthy food products to children, the proliferation of sedentary online activities, or food deserts (neighborhoods that lack healthy, affordable food options) that are more common in racial and ethnic minority neighborhoods."

Unprecedented epidemic of childhood and adolescent obesity

The new analysis estimates that older adolescent obesity prevalence rose substantially in the U.S. between 1990 and 2021, more than doubling in both males (from 8.8% to 22.7%) and females (from 10.1% to 28.8%).

In 2021, an estimated 15.1 million children and young adolescents and 21.4 million older adolescents were living with overweight or obesity.

However, they impact segments of the American population differently, with older adolescent females (50.8%) experiencing higher prevalence in 2021 than older adolescent males (46.7%), with especially high rates among older adolescent females in Mississippi, Alabama, and Oklahoma (where levels exceeded 59%), and among older adolescent males in Texas and West Virginia (where levels exceeded 52%).

The new study predicts that an additional 3.3 million children and young adolescents and 3.41 million older adolescents will be living with overweight or obesity by 2050 (raising the total to 43.1 million, of whom 24 million will have obesity).

With the increase in obesity projected to outpace the increase in overweight, around one in five children and at least one in three adolescents are expected to be living with obesity in 2050.

The rising tide of adolescent obesity is projected to reach the highest levels among older adolescent males in Oklahoma (43%), Mississippi (39.8%) and West Virginia (37.7%) in 2050, and affect at least half of older adolescent females living in Mississippi, Arkansas, Oklahoma, and Alabama.

However, the largest numbers of older adolescents with obesity will continue to be in California (1.53 million) and Texas (1.49 million) in 2050.

Associate Professor Ng said, "The mechanisms behind the rising obesity prevalence are much more complex than just a matter of excessive energy intake and physical inactivity. Existing interventions which focus on lifestyle-based behavioral changes do not produce sufficient and sustainable reductions in overweight and obesity, especially among children and adolescents.

"Addressing the structural drivers of population obesity and emphasizing prevention must be central to any future strategies. Future interventions also need to account for societal shifts in acceptance of obesity, alongside tailoring solutions by sex and for states with high obesity rates."

Population-level prevention and a cross-government strategy key to tackling obesity crisis

The analysis notes that while anti-obesity medications like glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have a place in obesity management, they alone will not be enough to solve the obesity epidemic.

As Associate Professor Ng explains, "Given the predicted surge in overweight and obesity, demand for anti-obesity medication will definitely increase, but it is not a silver bullet. With concern surrounding prohibitive costs and equitable access, together with varying effectiveness and potentially serious side-effects, prevention will remain a primary strategy."

The authors stress that prevention needs to become a much more dominant focus of obesity control and that any policies aiming to tackle the obesity crisis must be a priority at federal and state governments and backed by high-level political commitment.

They should also be comprehensive, reaching individuals across the life course and targeting inequalities. For example, given that obesity is intergenerational, the authors say that intervention needs to begin with pregnant women and early feeding practices.

"Rather than relying on individual agencies, stronger governance is needed to support and implement a multifaceted whole-system approach to radically disrupt the structural drivers of overweight and obesity at both national and community levels, as well as within households and schools," said Professor Gakidou.

"Federal policymakers must look beyond short-term political goals to target policy interventions not just within the health sector, for example, ensuring all children have access to nutritious primary school meals and that there is greater regulation of junk food marketing."

She added, "Above all, reversing the US obesity epidemic will rely on the government supporting programs that increase levels of physical activity, such as investing in safe and walkable neighborhoods, guaranteeing the availability of healthy food to children and adolescents, regulating the food and marketing industries, and achieving environmentally sustainable food systems."

The authors note some important limitations, including that while the study uses the best available data, predictions are constrained by the quality and availability of data, and for that reason, they were unable to estimate the prevalence of childhood overweight and obesity at the state level.

They also note that the definition of overweight and obesity is based on BMI, which might not account for variations in body structure across the population, and that they did not examine racial and ethnic disparities in obesity.

Finally, past trends are not always predictive of what will happen in the future, and some factors, like the recent surge in the use of GLP-1 anti-obesity medications could alter the longer-term forecasting trends of overweight and obesity.

Writing in a linked Comment, Professor Syvain Sebert from the University of Oulu in Finland (who was not involved with the study) said, "A multifaceted, whole-system approach is needed to address the overweight and obesity crisis, with the challenge that it has now surpassed every known level of epidemic progression.

"Extensive collaboration is needed across all health sectors, and both public and personalized health approaches need to be combined to confront and address the challenge together. There is great hope in new therapeutic approaches, such as GLP-1 analogs, for more effective and well tolerated treatments for overweight and obesity; however, these treatments should not be seen as a reason to abandon prevention efforts.

"Health-care systems cannot manage the epidemic solely through life-long secondary prevention policies … Hopefully this excellent new report will find its way onto the global policy agenda to aid in prevention efforts for all causes identified and all potential consequences of the obesity crisis."

More information: National-level and state-level prevalence of overweight and obesity among children, adolescents, and adults in the USA, 1990–2021, and forecasts up to 2050, The Lancet (2024). DOI: 10.1016/S0140-6736(24)01548-4 , www.thelancet.com/journals/lan … (24)01548-4/fulltext

Journal information: The Lancet 

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