New research finds long term weight loss success is more than possible — so long as you’re able to go under the knife.

Researchers tracked down the medical records of severely obese middle-aged veterans who had undergone a Roux-en-Y gastric bypass (RYGB) as far back as a decade earlier and compared their changes in weight to veterans who hadn’t experienced any surgery during the same time period. Ending up with more than 1,700 such patients and 564 who remained in the system ten years later (out of 700 originally), they found that only 3 percent of the latter group had climbed back to the weight they were prior to the surgery, with most keeping off the pounds they had lost. Over 70 percent of bypass patients lost and kept off at least 20 percent of their original weight a decade later, and nearly 40 percent had kept off at least 30 percent, which dwarfed the 11 percent and 4 percent of nonsurgical patients who accomplished the same, respectively.

A second comparison of weight loss outcomes between different types of surgery found that gastric bypass was more effective than either adjustable gastric banding or sleeve gastrectomy as well. The average amount of weight lost four years after the surgery was 28 percent for bypass patients, compared to 11 percent and 18 percent for adjustable gastric banding and sleeve gastrectomy patients, respectively. The researchers' findings were published Wednesday in JAMA Surgery.

“Bariatric surgery, especially RYGB, is effective at promoting long-term weight loss among obese patients,” they concluded.

Though many studies have shown substantial weight loss success and improved health outcomes from bariatric surgery, nearly all of these have only looked at patients a few years at most after their procedure. The current study is among the first, particularly in the U.S., to look at patients this much later into the future and to look at older men, with much of the previous research focusing on women in their 40’s. Earlier research has found similar long term success rates for gastric bypass, however. Sleeve gastrectomy, which involves removing two-thirds of the stomach, is a relatively new procedure so there hasn’t been as much opportunity to study its long term effects, while adjustable gastric banding has become less popular due to its relatively poor sustained success.

Promising as these results are, the researchers are quick to note that there’s still a lot we don’t know about the long term consequences of these very drastic procedures.

“More evidence is needed on postsurgical complications, disease resolution, and long-term mental health outcomes to help surgical candidates choose the procedure that is best for them,” they wrote. Indeed, a recent study published this July in the European Journal of Clinical Nutrition found that the mental health of bariatric patients had steadily declined in the ten years following their procedure, despite having achieved similar weight loss success as seen in the current study.

Ultimately, the researchers believe that weight loss surgery, regardless of how effective it may be, is a decision that shouldn’t be made lightly.

“Engaging patients in a high-quality shared decision-making conversation about their weight loss treatment options (including no treatment) is critical because prior studies have found that patients have unrealistic expectations of the weight loss that bariatric surgery will help them achieve,” they wrote.

Source: Maciejewski M, Arterburn D, Scoyoc L, et al. Bariatric Surgery and Long-term Durability of Weight Loss. JAMA Surgery. 2016.