To surgeons, fat has long been the tissue that gets pulled out of the way to clear space for the delicate work of repairing a heart or removing a tumor. Now, a new mouse study provides evidence that fat is more than just bodily bubble wrap.
The new work, led by researchers at Brigham and Women’s Hospital, shows that a short-term switch to a low-fat diet can change the way fat responds to the trauma of surgery—and perhaps could reduce complications and speed recovery.
The research builds off two ideas that have been percolating through medicine. First, it has become increasingly clear that drastic, long-term alterations in diet—such as adopting an extremely low-calorie diet—can have profound health effects, prolonging life in laboratory animals. Second, there has been a growing realization that fat is important for health, releasing hormones and other chemicals that help maintain balance in the body and are important for the immune system.
The researchers began to wonder whether one way of aiding patients’ recovery after surgery would be to prime them beforehand, with a short-term restricted diet.
“Over the last few decades, we’ve learned that if you minimize trauma to the liver, kidney, blood vessels, or heart when you operate, it helps accelerate people’s recovery from surgery,” said Dr. C. Keith Ozaki, a vascular surgeon at the Brigham. “We never really think of that fat tissue. We bore right through it, burn and yank it aside.”
In the study, published in the April issue of the journal Surgery, Ozaki and colleagues provide early evidence in mice that short-term changes in diet in the weeks prior to an operation can have biological effects that may translate to healthier recovery.
The researchers raised three groups of mice: one on a low-fat diet, another on a high-fat diet, and a third group that was raised on the high-fat diet and then switched to the healthier low-fat diet three weeks before surgery. Then, the researchers mimicked surgical procedures on each mouse. They cut into their fat, opened and closed a clamp several times in the animals, and burnt a section of fat tissue before stitching them back up.
The researchers found that the fat behaved differently in each case. In the high-fat group, genes involved in inflammation were very active compared with in the mice raised on the low-fat diet and production of specialized hormones decreased. But the mice that had eaten the low-fat diet for just three weeks had fat that behaved more like the fat tissue in mice that had been raised only on a low-fat diet, suggesting that even the temporary change had an effect.
Ozaki said that he hopes to move forward with pilot studies in people. Based on the animal research so far, Ozaki believes modifying a patient’s diet for as little as one week before surgery—for example, by cutting back on protein—might be a way to have a meaningful effect. In an accompanying paper, the scientists describe an idea they would like to test—whether the dietary restriction could be useful in reducing compliations after vascular surgery.
Valter Longo, a professor of gerontology at the University of Southern California who was not involved in the study, said that evidence is accumulating that short-term restricted diets can have beneficial health effects.
Longo’s laboratory is examining the role fasting plays in chemotherapy. Animal studies have suggested that fasting could offer protection from cancer drugs’ side effects and make the drugs more effective, and a phase one trial showing that the dietary intevention was safe in cancer patients recently completed.
He said the new work on surgery was well done, though preliminary.
“The point here was just to show that inflammation is reduced,” Longo said. “Inflammation is well known to contribute to the problems in recovery” from surgery. Ultimately, he said, the team needs to show in mice that the diet leads to better surgery outcomes, and test the diet in patients.