Long-Term Obesity Linked to Higher Heart Attack, Stroke Risk

We often hear that being overweight increases the risk of heart disease, but a study published in PLOS One suggests that how long someone carries excess weight may matter even more than their weight at a single point in time.

Using data from two large, long-running studies (Nurses’ Health Study and Health Professionals Follow-Up Study), a team of investigators followed more than 136,000 adults to examine how long-term exposure to excess weight affects the risk of major cardiovascular events, such as heart attack and stroke.

Instead of looking only at body mass index (BMI) at one moment, the team calculated “cumulative excess BMI,” a measure of how much and how long a person’s BMI stayed above 25 (the threshold for being overweight) over a 10-year period. They then tracked participants for cardiovascular events over the following years.

The findings showed that people with the highest long-term exposure to excess weight had a significantly higher risk of heart attack or stroke, especially at younger ages. For example, women under 35 and men between 35 and 50 with the highest cumulative weight exposure had up to a 60% increased risk compared with those with lower exposure.

“Excess weight at any given point in time is not a life sentence,” said study investigator Alexander Turchin, M.D., M.S., of the Division of Endocrinology in the Mass General Brigham Department of Medicine. “What happens to someone’s weight over long periods of time matters more for heart health. Our study suggests that if a person lowers their weight, their health outcomes can improve.”

Interestingly, a person’s BMI at the start of the study alone was not a strong predictor of risk once long-term exposure was considered. This suggests that the duration of being overweight may be more important than a single weight measurement.

The increased risk was most noticeable in younger and middle-aged adults, while it was less clear in older age groups. Researchers say this may reflect how long-term exposure earlier in life can have lasting effects on heart health.

Investigators noted several strengths that make its findings more reliable. It included a very large number of participants and followed them over many years, which allowed the team to look closely at differences by age and sex. The data were collected over time (rather than relying on memory), with very little missing information, helping reduce bias. In addition, outcomes like heart attack and stroke were carefully verified in the original studies, which improves the accuracy of the results.

However, there are also important limitations to consider. Participants reported their own height and weight, which can sometimes be inaccurate. The study population also lacked diversity, with most participants having similar socioeconomic backgrounds and a majority being women, which may limit how well the findings apply to other groups.

Another key limitation is the use of BMI as the main measure of weight. While BMI is widely used, it doesn’t always reflect body fat distribution, such as harmful fat around organs, which may be more closely linked to health risks. This means the results may not fully apply to people whose BMI doesn’t accurately represent their body composition. Lastly, because this was an observational study, it can show a link between long-term excess weight and heart risk, but it cannot prove that one directly causes the other.

The study highlights the importance of maintaining a healthy weight over time, not just in the short term. Preventing or reducing long-term excess weight, especially earlier in adulthood, could play a key role in lowering the risk of serious cardiovascular events later in life.

“These findings should give patients and their clinicians an impetus to address excess weight to improve their long-term health,” concluded Turchin.