Can you starve cancer cells with a low-carb diet? A clinical trial seeks to find out

• Scientists think that a fasting-mimicking diet might boost chemotherapy treatment.
• The hope is two-fold: that the diet might ease side effects, and improve treatment outcomes.
• One woman who tried the diet in a clinical trial for breast cancer shares her experience.

Reproductive cancers run in Jeannie Kim's family. Her dad had pancreatic cancer, her grandfather had gastric cancer, and aunts on both sides of her family have had breast, uterine, and ovarian cancers.

When she was 55 years old — the same age at which her dad died of cancer — Kim went in for a routine mammogram, and by the next month, she was diagnosed with an aggressive form of stage 2B breast cancer, with a 2.5-centimeter tumor in her chest. Doctors had discovered she carries one of the key BRCA2 gene mutations that drives breast and ovarian cancer risk.

Within just a few weeks, she was undergoing chemotherapy. But alongside her treatment, Kim decided to try something experimental, aimed at helping ease the well-known, debilitating side effects of toxic chemotherapy: a fasting -mimicking diet.

The diet is meant to trick the body into thinking it's not eating, while still getting some nutrition every day. Scientists believe this diet may trigger a cellular cleanup process that essentially starves cancer cells, while keeping the "healthy" cells of the body functioning well. It's a strategy that's been tested and proven in laboratory experiments, but it's still unclear whether it actually works on people.

Kim is part of one of the first big research studies trying to decipher whether this technique is real. Over the course of roughly 12 years, she and 94 other women have tried a specific low-carb diet during chemotherapy. Their doctors look for improvements in their immediate chemo side effects, like less nausea and vomiting, as well as long-term cancer treatment outcomes.

Scientists want to know: can this 5-day diet improve not only how you feel when you're going through chemo, but also make the cancer treatment itself even more powerful?

One woman's experience on the 5-day, low-carb diet for chemo

During the five-day fasting-mimicking program, Kim ate specially formulated soups, plus oily nut bars for breakfast, and some crunchy kale crackers, which were by far the most savory part of the meager meal plan, she said. It was certainly not the most "delectable" cuisine she'd ever had, but it was palatable.

The low-calorie, low-protein, high-fat meals are designed to trick your body into thinking you're not eating. Ideally, it will start that self-eating process called autophagy.

"The soups, nothing to write home about," Kim said. "They are powdery, pasty, not the most delectable things on the market by any stretch of the imagination. They're palatable."

But during chemo, she didn't mind so much.

"When you don't have an appetite and your taste buds are crappy already to begin with, swallowing this stuff was just like, 'I'm drinking medicine.' That was the mentality."

Kim still had other classic chemo side effects. She lost her hair, had extreme neuropathy pain, and experienced an allergic reaction to one of the drugs.

But Kim also said she didn't have the same nausea, vomiting, and dehydration issues that so many patients suffer when they're doing chemotherapy.

"What the fasting protocol did was it helped with the stomach aspect of it," Kim said. "I was able to continue to pursue and do things that the average person in my situation would not have been able to do."

Can you starve a person's cancer cells? Some scientists are skeptical

"My results were phenomenal," Kim told Business Insider. "I wasn't vomiting. I wasn't as sick as most people are."

Independent experts are less glowing. They say this technique has promise, but it's far from settled science.

"This is a great thing to be studying, but is not something that there is enough evidence that people should just be doing this," Dr. Jennifer Ligibel, an associate professor of medicine at Harvard Medical School who co-authored the guidelines American doctors use to guide decisions about diet and exercise during cancer treatment, told Business Insider.

Scientists think that the hibernation our cells go into when we're fasting might be a boon for cancer treatment , the perfect opportunity to literally starve cancer, while still keeping the body running.

"That's kind of the theory behind this: that you're protecting your normal cells with the fasting, but that the cancer cells don't have that same kind of alternative metabolic pathway and so that they are then more affected by the chemotherapy than your normal cell," Ligibel said.

Ligibel said there's good reason to think that this technique might work for people, and not just lab mice. However, she still has concerns.

On this diet, you're getting just 10% of your calories from protein. That is at the very lowest end of what's recommended to keep muscles strong and the body nourished. Ligibel worries about the potential for too much muscle loss.

Ultimately, Ligibel says, the current evidence isn't strong enough to support trying this outside of a well-monitored trial setting.

There are other evidence-backed ways to soften the blow of chemo

Another tactic Kim religiously adopted during her chemo treatment — regular exercise — is something Ligibel has no problem getting behind.

"There is such good data that exercise, both aerobic exercise and strength training during chemotherapy is incredibly important to reducing side effects and helping people maintain their strength and function," she said. "Specifically during chemotherapy radiation."

After each of her treatments, Kim would walk at least a mile along the beach.

"Sometimes I needed support, sometimes I didn't," she said. "But I think that, too, helped me in terms of being able to have a much better recovery and much better prognosis."

In addition to reducing side effects and helping people maintain their strength and function, regular exercise just helps people feel good.

Ligibel says it's impossible to know how much of Kim's relatively mild side effect profile can be chalked up to the diet, how much might be because of her exercise, and how much might be due to other factors, including her specific genetics and environment.

Only the results of the big, controlled study, with plenty of other people in it, will be able to begin to disentangle some answers.

Kim has been cancer-free for two years now. She says she's told a lot of people about the 5-day system, developed by USC professor Valter Longo , a pioneer of fasting-mimicking diets.

"When any organism fasts, there's a process of it shrinks — something called autophagy — it shrinks and stands by and is just waiting for food. Kind of like, imagine a hibernating bear," Longo told Business Insider.

Once our "bear" comes out of hibernation, the hope is that cancer cells will be dead, and the healthy cells left over will regenerate and revitalize themselves.

"The most powerful part happens when the body re-expands," Longo said.