The study, conducted by researchers from the Karolinska Institute in Stockholm, Sweden, found that the savings made on medication and healthcare as a result of weight loss surgery meant that the overall cost of treating diabetes did not increase.
For the current study, Neovius and colleagues followed 4,030 patients for about 15 years. Roughly half of them received bariatric surgery, while the rest did not.
Within each group at the start of the study, many patients did not have diabetes, while some had elevated blood sugar that suggested they might be at risk for developing the disease and others already had full-blown diabetes.
"Greater weight should be given to preoperative blood sugar status to help identify the patients who have the most benefit from bariatric surgery," study co-author Martin Neovius of the Karolinska Institute in Stockholm said by email. "We have shown previously that this makes sense from a health outcomes perspective, and now we show that it makes sense also from an economic perspective."
When people without full-blown diabetes got bariatric surgery, their treatment costs including the operations and follow-up care were higher than similar patients who did not have the procedures.
But for diabetics, the costs for the surgery group and the nonsurgical group were roughly the same after 15 years. The cost of surgery was largely offset by less use of healthcare and lower prescription drug costs, the study found.
Globally, 1.9 billion adults are overweight or obese, according to the World Health Organization (WHO). Obesity increases the risk of heart disease, diabetes, joint disorders and certain cancers.
According to the WHO, one in nine adults have diabetes. Most of these people have Type 2 diabetes, which happens when the body can't properly use or make enough of the hormone insulin to convert blood sugar into energy.
Left untreated, diabetes can lead to nerve damage, amputations, blindness, heart disease and strokes.
A growing number of extremely obese patients have turned to surgery after failing to achieve significant weight loss through diet, exercise or medication - strategies that can also manage diabetes. Like all surgery, it is not risk free, and bariatric operations in particular carry a risk of malnutrition.
Clinical guidelines used in many parts of the world only recommend bariatric surgery for patients who are extremely obese, based on a measure of weight relative to height known as body mass index (BMI).
An obese adult who is 5 feet 9 inches tall would weigh at least 203 pounds and have a BMI of 30 or more, for example. Only adults with a BMI greater than 40 should get bariatric surgery, according to widely followed recommendations from the U.S. National Institutes of Health, although some patients with serious health problems, including diabetes, may be candidates with a BMI over 35.
One limitation of the study is that it relied in part on self-reported drug costs, and lacked data on costs related to nonprescription drugs, nursing homes, medical equipment and certain services like dietitians and psychologists, the authors acknowledge in The Lancet Diabetes and Endocrinology.
The researchers have revealed, "to our knowledge, this is the first prospectively controlled study to assess long-term healthcare costs in obesity surgery patients according to their preoperative diabetes status versus matched controls."
"We show that for obese patients with type 2 diabetes, the upfront costs of bariatric surgery seem to be largely offset by prevention of future health-care and drug use. This finding of cost neutrality is seldom noted for health-care interventions, nor is it a requirement of funding in most settings."