Regardless of lifestyle and other health-related factors, heavier people were more likely than lean ones to be hospitalized for a variety of conditions, according to an Australian study.
What's more, this was the case not just for obese people but also for those who were merely overweight as well, the researchers wrote in the International Journal of Obesity.
Among middle-aged adults, researchers found that every extra body mass index (BMI) point - equal to about 2.7 to 3.2 kilograms (six or seven lbs) - was tied to a four per cent higher chance of being admitted to the hospital over a two-year period.
"There is considerable evidence that severe obesity is bad for your health, resulting in higher rates of disease and consequently higher use of health services and higher death rates," said lead author Rosemary Korda, from the Australian National University in Canberra.
"What this study shows is that there is a gradual increase in risk of hospitalization as BMI increases, starting with people in the overweight range. In other words, even being overweight (but not obese) increases your risk."
Korda and her colleagues recruited close to 250,000 people aged 45 and above from New South Wales. After surveying them about their height, weight and other health and lifestyle issues, the researchers tracked participants through hospital data.
Over the next two years, they had more than 61,000 total hospitalizations lasting at least one night.
Korda's team found that among people considered in the normal range for BMI, there were 120 hospitalizations for every 1,000 men and 102 per 1,000 women each year. For those considered severely obese, on the other hand, there were 203 hospitalizations for every 1,000 men and 183 per 1,000 women, on average.
Overweight and moderately obese people had hospitalization rates somewhere in between.
A BMI of 25 to 30 is classified as overweight, while obese is from 30 on up.
That pattern held up even after taking into account whether participants smoked, how physically active they were and their general health at the start of the study.
Extra weight seemed especially to play a role in people's chances of being hospitalized for diabetes, heart disease, chest pain, arthritis and asthma, the researchers reported.
"Extending the research to overweight individuals... is a unique contribution," said Robert Klesges, a preventive medicine researcher from the University of Tennessee Health Science Center in Memphis.
"Basically it tells tens of millions of Americans that, 'you are now at risk'," added Klesges, who wasn't involved in the study.
According to the Centers for Disease Control and Prevention, just under 36 per cent of American adults are obese. Another 33 per cent are overweight.
"While increasing weight leads to increasing risk, this also means that a gradual decrease in weight is likely to gradually decrease your risk - ie, if you are overweight or obese, even small decreases in weight may make a positive difference to your health," said Korda.