For years, medical professionals have stressed the importance of maintaining a healthy body mass index (BMI).

While some contend there are more important numbers to focus on, research tells us that a higher than normal BMI could be linked to all sorts of health conditions.

Now, it turns out those conditions might include some types of cancer.

A study in Cancer Letters found that the growth and spread of multiple myeloma increases as a person’s BMI rises.

About 10 percent of all blood cancers are multiple myeloma. Doctors typically detect it with blood tests, though biopsies can be used as well.

In 2015, researchers in Sweden published a report in Cancer Cell about a blood test they developed that accurately detected cancer 96 percent of the time. It also specified the type of cancer detected with 71 percent accuracy.

"Once a person with cancer is out of the normal weight category, their BMI is contributing to multiple myeloma growth and progression," said Katie DeCicco-Skinner, associate professor of biology at American University and lead study author.

While BMI can’t help doctors detect the cancer — laboratory tests do — the finding could help doctors better treat overweight and obese cancer patients.

“Fat cells from overweight, obese, or morbidly obese individuals all enhanced factors linked to cancer progression more than fat cells from normal weight individuals,” DeCicco-Skinner told Healthline. “Even a BMI in the overweight category could accelerate cancer progression.”

She said that numerous epidemiological studies have shown that obese people are more likely to develop multiple myeloma as well as have significantly shorter overall survival.

“BMI is a risk factor for multiple myeloma,” she stated.

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How fat encourages cancer

In her study, DeCicco-Skinner’s team found that fat cells communicate differently with multiple myeloma cells as BMI goes up.

That’s because fat cells grow larger, gain additional lipid, and secrete proteins linked to cancer.

The researchers also found a correlation between BMI and angiogenesis and adhesion, key indicators of cancer progression.

The findings could change how overweight and obese cancer patients receive treatment. What may be the appropriate dose of chemotherapy or other drug treatments in an individual of normal weight may not be the optimal dose in an obese patient.

“Doctors may need to treat obese multiple myeloma patients with drugs that target specific obesity-related factors or consider drug interactions since many obese patients may be taking other drugs to treat obesity-associated conditions such as diabetes,” DeCicco-Skinner said.

Multiple myeloma isn’t the only cancer tied to being overweight or obese.

Excess weight is also linked to breast, colorectal, esophageal, endometrial, kidney, and pancreatic cancers, among others, DeCicco-Skinner said.

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Watch your weight, lower your risk

Dr. Eugene Ahn, an oncologist at the Cancer Treatment Centers of America at Midwestern Regional Medical Center in Illinois, said obesity raises our cancer risk due to many mechanisms.

Those include immune system function as well as hormone and inflammation levels.

Most people may not know there is a connection between obesity and cancer risk.

“After tobacco use, obesity has been identified as the second leading preventable cause of cancer,” Dr. Sara Mijares St. George, an oncologist at the Sylvester Comprehensive Cancer Center in Florida, told Healthline.

“Not only has obesity been linked to risk for developing several types of cancer, it has also been associated with poorer treatment outcomes and increased mortality in those with cancer,” St. George said.

She said that obesity-related cancers make up 27 percent of the total cancer burden.

Mortality from all types of cancer is 52 percent higher in severely obese men and 62 percent higher in severely obese women compared to people in the normal weight range.

Ahn added that excess weight could also cause complications from chemotherapy, radiation, and surgery.

He said weight loss isn’t an alternative treatment for cancer, but it can help improve cure rates for those who receive definitive conventional therapy.

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