What the heck is cancer metabolism?

Google the signs and symptoms of endometrial cancer, and you’ll discover ‘losing weight without trying’ in the top three or four. For me, it was one of the ways I knew something wasn’t right in my body.

At the end of August, I came home high on the endorphins of running camp — a weekend in the northern Pennsylvania woods with accomplished women who share your passion for running is something I encourage everyone to experience. Camp gives you the chance to run 2-3 times each day, and even if you don’t do doubles, your Garmin will be evidence that you’ve amped up your activity level from your baseline. Despite eating all the great food, I wasn’t surprised I was a few pounds lighter when I hopped on the scale as I got out of the shower on the first morning I was home.

But two weeks later I was a few more pounds lighter, and by the time my clinic appointment rolled around in early October, my scale was reading ten pounds lighter. I’m not a person who loses weight easily unless I make a concerted effort as part of a training block, and then I’d lose 10 pounds over a three to four month period by changing diet and upping my running volume. This wasn’t the case here.

It was enough for me to mention to my doctor about other changes I’d noticed besides spotting, and when I had my biopsy appointment, my gynecologist connected dots that might have been a trigger for my symptoms.

In post-menopausal women most of our estrogen is produced by fat tissue. Weight loss shifts this balance and can trigger spotting. It’s a bit of a chicken and egg thing though — is the weight loss a trigger or a symptom? I’ve known rapid weight loss as a means of losing your period as an athlete, not the reverse. My gynecologist simply described it as ‘relevant information’ to include in my file as we investigated further.

All this has taken me down the rabbit hole of learning about the links between cancer, carbs, and lactate. I know nothing about cancer and metabolism, and what I know about carbs and lactate I’ve acquired from 10 years of running and racing.

Is this the reason for my sweet tooth?

I love to cook. And to garden. I make Greek yogurt from scratch each week. It’s a combination that means I eat healthy on the average day. I’ve experimented with different ways of eating — I tried keto for awhile to manage inflammation. But mostly I stick with whole foods and meals made from scratch.

It’s also true though that I have a sweet tooth that needs to be fed periodically. My drug of choice is Lifesaver Gummies. They are great fuel on a long run but eating the whole bag while you watch your favorite show won’t meet any nutritionist’s approval.

I’m interested to learn more about blood sugar as a factor in my cancer. Research shows a link between glucose dysregulation and the growth of endometrial tumors. This is one of the reasons why obesity and diabetes rank as significant risks. Current science suggests too much sugar in our diet and a sedentary lifestyle impacts the level of obesity, and that condition sets the stage for cancer to develop more easily. Mitigating those risks by lowering your blood sugar makes logical sense as a preventative measure, but whether sugar directly feeds cancer cells is less clear.

I’m not ready to give up my Lifesaver Gummies as fuel for a long run. But I am paying closer attention to what sugar goes into my body as part of my regular diet.

And I am asking the question how my own metabolism is changing as a consequence of this cancer in my body.

What does this mean for my running?

Compared to normal cells, cancer cells have a different metabolism – their rate of glycolysis is significantly higher, meaning they produce more lactate as a consequence.

Cancer cell or not, glycolysis is the process by which lactate is formed as glucose is converted into energy. If you’re a distance runner, you’re familiar with that burning sensation in your legs as lactate builds up faster than your body can use it. Speed workouts are where I feel this effect most often. Through training you can adapt your lactate threshold, getting to better performance levels before that burn kicks in.

The worrying bit I encountered is the research that describes lactate as a key in oncogenesis — the process by which normal cells become cancer. If running hard increases lactate output, and lactate is bad in the context of cancer growth, doesn’t that mean, by extension, that running is bad for cancer patients?

It turns out it’s not so simple.

Studies show that running can be a way of mitigating risk. Exercise may also be a tool in managing cancer progression. Just as you can train your lactate threshold to achieve better athletic performance, that same effect may help the body when the aim is to disrupt the loop that promotes tumor growth. By using lactate more efficiently, so it doesn’t build up in the body, are we essentially reducing the available fuel supply for cancer cells to develop? Bringing insights from exercise physiology to the study of cancer seems promising — enough for me to have added it to my list of questions for the next time I see my doctors.

Where do we go next?

Some days I feel like the poster child for this diagnosis — 60 years old, no children, early periods (I was 10 going on 11), late menopause (55 or 56), and overweight for my entire adult life. When they were still happening, my periods were often heavy and hard to manage. I’m still surprised that I never knew — until after I was diagnosed — that taken together, this put me at higher risk for endometrial cancer. We have a lot of work to do to create the same level of awareness about endometrial cancer as we have created for breast, ovarian and cervical cancer.

I’m fortunate to have access to excellent medical care, and to be able to afford additional services through my insurance. I had already planned to investigate what exercise would help me maximize my recovery and return to running. Now, I’m adding questions about how my running might be used as a tool to manage my cancer and mitigate recurrence.

I’m only beginning to wrap my head around all this information. It’s all fodder for how I approach managing this diagnosis, treatment, and the path forward. Even with the best results from surgery, with no need for chemo or radiation, I’ll have two to three years of regular monitoring every three to four months, and then switching to every six months. Annual checkups will only return after five years if all goes well. I need to get comfortable with the reality that I’ll be navigating a lot more medical appointments than I’m used to.

For now, I have more questions than I have answers – about how this disease affects my own metabolism, and what are the unique characteristics of the cancer’s metabolism itself.