Why A Little Extra Weight May Help Seniors Survive Surgery

Seniors who are considered overweight are more likely to survive elective surgery, research shows. (Photo by Gorodenkoff on Shutterstock)

Three Out of Four Underweight Seniors In Study Died After Surgery, While Overweight Patients Fared Best

LOS ANGELES — For years, doctors have repeated a familiar message: if you’re heading into surgery, shedding pounds could improve your odds of a smooth recovery. Hospitals often encourage patients to slim down before elective procedures, citing risks like infection, heart strain, and breathing difficulties in heavier individuals. But a study from UCLA suggests that this advice may not apply equally to everyone. For older adults, carrying a little extra weight may actually improve the chances of surviving surgery.

The study followed more than 400 adults over age 65 who underwent major operations at a Los Angeles hospital. When the researchers compared outcomes across weight categories, they found something surprising. Seniors in the “overweight” range (a body mass index (BMI) between 25 and 29.9) had the lowest risk of dying within 30 days of their procedures. In fact, only one out of 128 overweight patients died in the month after surgery. By contrast, 25 out of 133 patients with a “normal” BMI did not survive, a rate nearly 20 times higher.

“Our study findings challenge the traditional belief that attaining a normal BMI (18.5–24.9) is ideal before major elective surgery for older adults,” the authors wrote in their paper, published in JAMA Network Open. Instead, the results suggest that for seniors, a little extra weight may sometimes be protective.

Rethinking the ‘Normal’ Weight for Seniors

BMI is a simple ratio of weight to height. For adults, a BMI of 18.5 to 24.9 is considered “normal,” 25 to 29.9 is “overweight,” and anything above 30 is “obese.” Health campaigns often frame “normal” weight as the gold standard. But this study suggests that for seniors, those categories may not tell the full story.

At the other end of the scale, the results were grim. Patients who were underweight (BMI below 18.5) fared the worst of all. Fifteen out of 20 underweight patients died within a month, giving this group the highest mortality rate by far. By comparison, the overweight group had the best outcomes.

The findings highlight a critical point: the meaning of “healthy weight” changes with age. Older adults lose muscle mass, often shrink in stature, and experience shifts in fat distribution. A thin body at 70 or 80 may not reflect youthful fitness but rather declining reserves that make it harder to withstand stress.

The researchers, led by Dr. Cecilia Canales, assistant professor in the Department of Anesthesiology & Perioperative Medicine at the David Geffen School of Medicine at UCLA, can’t say for certain why overweight patients survived at higher rates, but several theories make sense. Surgery places enormous stress on the body. Blood loss, anesthesia, and healing demands drain energy reserves. Having extra fat and muscle may give seniors more of a cushion, literally buying them time to recover.

Nutrition also plays a role. Older adults with slightly higher weight may have better stores of protein and vitamins that the body can draw on to repair tissues and fight off infection. In contrast, thinness in older adults is often a warning sign of hidden illness. Conditions like cancer or heart disease can cause unintentional weight loss, leaving patients weaker and less able to recover after an operation.

The authors explain: “Older adults, particularly frail individuals, may benefit from being in the overweight category.” That idea, often called the “obesity paradox,” refers to the counterintuitive observation that carrying some extra weight can sometimes protect rather than harm, depending on the situation.

The study doesn’t suggest that heavier is always better. At the highest end of the scale, problems piled up. Seniors with morbid obesity (BMI 40 or above) didn’t necessarily die at higher rates, but nearly eight in ten developed complications. Lung issues like pneumonia and breathing trouble were especially common, along with blood clots and strokes.

So, while being moderately overweight seemed protective, extreme obesity still posed major risks. The “sweet spot” in this study was firmly in the overweight category, not in obesity’s upper ranges.

Frailty Adds Another Layer

The UCLA team also looked at frailty — a measure of overall resilience that considers factors like strength, energy, and chronic illness. About a quarter of the patients were classified as frail, while more than a third were “pre-frail.”

Interestingly, the survival benefit of being overweight showed up even among the frailest patients. That suggests the advantage wasn’t just about younger, healthier seniors being heavier — it applied across different health levels.

Weight Loss Ahead of Surgery Could Backfire

These findings raise tricky questions for doctors and patients planning surgery. Many hospitals still recommend or even require weight loss before elective procedures, believing it reduces risks. But for seniors, those delays may backfire. Waiting months for weight loss programs could give underlying diseases time to progress, ultimately making surgery more dangerous.

The researchers also dug deeper into the “normal” weight group by splitting it in half. Nearly all deaths and complications occurred among seniors in the lower end of normal BMI (18.5 to 22.5). Those closer to the top end of normal (22.5 to 24.9) fared much better. This pattern suggests that the biggest danger may lie not in being overweight but in being too thin.

Still, the authors caution that these findings shouldn’t be taken as a free pass to gain weight. As they write, “The obesity paradox does not imply that obesity is protective overall, rather, it highlights the complexity of how weight, fat distribution, and muscle mass interact with specific disease processes and outcomes.”

Important Caveats

As striking as the results are, the study does have limits. It was relatively small, involving just 414 patients at a single academic hospital. The underweight and morbidly obese groups were especially small, so their numbers may not translate widely.

Another limitation is BMI itself. The measure doesn’t distinguish between fat and muscle or reveal where fat is stored in the body. A muscular older adult and a frail patient could have the same BMI but very different health profiles. Finally, because the study is observational, it can’t prove that carrying extra weight directly caused better outcomes, only that the two were linked.

A Changing View of Weight and Aging

Despite those caveats, the study adds to a growing body of research suggesting that the “ideal” weight for seniors is not the same as for younger adults. Public health guidelines tend to focus on reducing obesity-related disease in middle age, but in later life, the dangers of being underweight may loom larger.

With the U.S. population rapidly aging, these findings matter. More seniors are undergoing surgery than ever before, from hip replacements to cancer operations. Understanding how weight affects outcomes could help doctors tailor recommendations more precisely.

“Future investigations should also explore how BMI interacts with other critical factors, including nutritional status, muscle mass, and frailty, to refine preoperative optimization strategies,” the authors conclude.

In other words, it may be time for doctors to look beyond the scale when preparing older patients for surgery. For some seniors, a few extra pounds could mean the difference between life and death.

Disclaimer: This article summarizes peer-reviewed research and is for informational purposes only. It is not medical advice. Patients should consult their doctors before making decisions about surgery, weight, or other health concerns.