Explained: Why 75% US adults are now overweight or obese

The study authors were particularly alarmed by the steep rise in obesity among children, more than 1 in 3 of whom are now overweight or obese.

The paper defined “overweight” adults as those who were age 25 and over with a body mass index at or over 25, and “obese” adults as those with a BMI at or over 30. (Source: Unsplash)

Nearly three-quarters of the adult population in the United States is overweight or obese, according to a sweeping new study. The findings have wide-reaching implications for health and medical costs as the US faces a growing burden of weight-related diseases.

The study, published in The Lancet on Thursday, reveals the striking rise of obesity rates nationwide since 1990 — when just over half of adults were overweight or obese — and shows how more people are becoming overweight or obese at younger ages than in the past.

Both conditions can raise the risk of diabetes, high blood pressure and heart disease, and shorten life expectancy.

The study (‘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’: GBD 2021 US Obesity Forecasting Collaborators) documented increases in the rates of overweight and obesity across ages.

The study authors were particularly alarmed by the steep rise in obesity among children, more than 1 in 3 of whom are now overweight or obese. Without aggressive intervention, they forecast, the number of overweight and obese people will continue to go up — reaching nearly 260 million people in 2050.

The paper defined “overweight” adults as those who were age 25 and over with a body mass index at or over 25, and “obese” adults as those with a BMI at or over 30.

The authors acknowledged that BMI is an imperfect measure that may not capture variations in body structure across the population. But from a scientific perspective, experts said, BMI is correlated with other measures of body fat and is a practical tool for studying it at a population level.

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The authors found a steady increase in the share of people who are overweight or obese over the past three decades. The rate of obesity in particular rose steeply, doubling in adults between 1990 and 2021 to more than 40% — and nearly tripling, to 29%, among girls and women aged 15 to 24.

The implications are serious: A Joint Economic Committee Republicans report released this year predicted that obesity will result in up to $9.1 trillion in excess medical expenditures over the next 10 years. Obesity increases the likelihood of numerous metabolic conditions and their associated complications. It is also linked to infertility, cancer and poorer mental health outcomes.