.LONDON (AP) – Preventing obesity and smoking can save lives, but it doesn’t save money, researchers reported Monday.

It costs more to care for healthy people who live years longer, according to a Dutch study that counters the common perception that preventing obesity would save governments millions of dollars.

“It was a small surprise,” said Pieter van Baal, an economist at the Netherlands’ National Institute for Public Health and the Environment, who led the study. “But it also makes sense. If you live longer, then you cost the health system more.”

In a paper published online Monday in the Public Library of Science Medicine journal, Dutch researchers found that the health costs of thin and healthy people in adulthood are more expensive than those of either fat people or smokers.

Van Baal and colleagues created a model to simulate lifetime health costs for three groups of 1,000 people: the “healthy-living” group (thin and nonsmoking), obese people, and smokers. The model relied on “cost of illness” data and disease prevalence in the Netherlands in 2003.

The researchers found that from age 20 to 56, obese people racked up the most expensive health costs. But because both the smokers and the obese people died sooner than the healthy group, it cost less to treat them in the long run.

On average, healthy people lived 84 years. Smokers lived about 77 years, and obese people lived about 80 years. Smokers and obese people tended to have more heart disease than the healthy people.

Cancer incidence, except for lung cancer, was the same in all three groups. Obese people had the most diabetes, and healthy people had the most strokes. Ultimately, the thin and healthy group cost the most, about $417,000, from age 20 on.

The cost of care for obese people was $371,000, and for smokers, about $326,000.