Excess body fat, particularly the kind that accumulates around the belly, increases the risk of at least a dozen cancers —pancreatic, colorectal, advanced prostate and breast cancer in us older women. If you already have cancer, it can worsen the prognosis.
So what can you do about it?
Recently, at the AICR’s 26th annual conference, researchers from around the world shared their insights on how body fat fuels the underlying processes that cause cancer to proliferate. The key? Inflammation and growth promoting hormones, says Harvard’s Dr. Edward Giovannucci-— factors within your control.
Svelte readers, stick around for the story. You may be among the small group of people scientists are calling “the skinny fat.”
Ring Around the Belly: How Abdominal Fat Makes Cancer Cells Immortal
Ring Around the Belly, the scourge of us women post menopause, is a sign that your body is in metabolic mayhem. The way your cells are burning fuel for energy is all mucked up.
You’re taking nutrients from food and turning them into hormones that tell cells, including cancer cells, to grow, grow, grow– and not to die like every good cell should.
Insulin is a major culprit, says keynote speaker McGill University’s Dr. Michael Pollak.
Take a normal cell. Once it divides about 50 to 60 times or if it becomes damaged and can’t repair itself, it commits suicide, or apoptosis. Cancer cells refuse to die.
Over the past decade, scientists have identified a dozen or so underlying cell signalling pathways that keep cancer cells immortal–that is, growing and accumulating mutations that enable them to spread. Insulin turns on a major growth pathway. It flips open a molecular switch, called the mammalian target of rapamycin (mTOR), that allows cells to continually send internal messages saying “grow, cell, grow.”
Insulin stimulates about 75 percent of cancer growth, says Pollak, who studies various hormones that are elevated in response to nutrients and cause cancer cells to proliferate. (Insulin Growth Factor-1, which acts like insulin, and sex steroid hormones such as estrogen and testosterone, are other such hormonal messengers.)
Pollak explains: Many cells in the body, both normal and cancerous ones, have receptors for insulin. And when insulin’s abundant, your cells respond by doing what they’re designed to do. Epithelial cells, which line the surfaces of tissues and are the source of most cancers, keep on dividing–thus growing. Fat cells, in the presence of insulin, store fat– especially around the abdominal organs.
And here’s the rub: Belly fat is biologically active; it secretes compounds that magnify your problems handling insulin, that trigger inflammation throughout your body and that tell cells to grow.
In other words, more insulin =more and bigger fat cells=more insulin and inflammation=more fat, and on and on. That’s what scientists call a positive feedback loop–an escalating, self-fueling, destructive tornado, like the “The Dance of Anger” described so wisely by another Harriet (last name Lerner, not Sugar, but both equally appropriate, don’t you think?)
Granted, not everybody who is overweight is metabolically challenged. And a percentage of people who are normal weight or even thin are actually considered metabolically obese– the “skinny fat,” in scientists’ slang. So how can you know if you have a problem with insulin? Doctors should be measuring insulin levels after you eat, says Pollak. (His second choice of markers: C peptide proteins.)
To get off the treadmill that’s wreaking havoc with your metabolic health, AICR scientists have two main suggestions: Up your exercise and change your dietary patterns.
Kickstart your Metabolism: Physical Activity
The good news is that independent of body weight, physical activity can help lower cancer risk and increase survival, says Penn State’s Dr. Connie Rogers.
The prescription: aerobics and resistance training. For survivors, at least 150 minutes of moderate intensity exercise spread throughout the week and resistance training with weights twice weekly improved the metabolism of women with breast cancer in this four month study.
Exercise can reduce belly fat and obesity-related cancers. It can reduce side effects of treatment and improve treatment outcomes. It seems to work, at least in part, by lowering inflammation, insulin and other growth promoting hormones and improving immune status.
Strengthening muscles is vital. Muscles are critical to getting insulin out of your blood. (Plus, when muscles are contracting, they act as a filter to remove circulating tumor cells, says Rutger’s Dr. Thomas Findley. That’s why you never see cancers in the heart. )
Let’s say you’ve just enjoyed dinner. As your blood sugar rises, your pancreas produces insulin. Like a freight train, insulin transports glucose from your blood into cells that use glucose for fuel. Muscles love glucose.
But when harmful fats build up inside of muscle cells, the train of insulin gets blocked from entering. Instead of taking sugars into cells, insulin– and glucose–start puddling in your blood. That’s Insulin Resistance, muscles resistant to the actions of insulin, the first step in the metabolic fury known as “Metabolic Syndrome.” The pancreas keeps working harder and harder, trying to pump out insulin to transport glucose, and eventually poops out. You’ve now got Diabetes, Type 2– a condition that can lead to heart disease and many kinds of cancer, as AICR dietitian Karen Collins has been discussing for years .
Kickstart Your Metabolism: Plants, “Lupper” and other Promising Dietary Patterns
More good news: A little weight loss can go a long way in improving your metabolic health, according to Dr. Giovannucci. But it may not be the weight loss per se that does the trick. Shutting off incessant mTOR signalling could be the key, says UNC’s Dr. Stephen Hursting, citing his studies in animal models.
Here are some guidelines for dietary patterns that emerged from three days in Blue Heaven (Chapel Hill, NC, the site of this year’s conference and my alma mater):
1/ Eat plants, says Texas A&M’s Dr. Robert Chapkin—a pattern that AICR and its sister organization, the World Cancer Research Fund, have been recommending for a long while. Weill-Cornell’s Dr. Andrew Dannenberg echoed that suggestion. He’s hoping to do clinical trials to test the effects of plant-based diets and physical activity on women with early stage breast cancer.
Unlike animals, plants contain a combination of fiber and phytonutrients that create a garden of healthy immune cells in your gut– tamping down inflammation and controlling insulin by slowing the release of glucose into your blood. According to Germany’s Dr. Bodo Melnik (not at the conference but among my top picks for next year’s guests), there’s evidence that some plants help close the mTOR switch:
- green tea
- whole soy
- resveratrol-rich grape skins and berries, and, drum roll please for,
- crucifers. As at past AICR conferences, crucifers garnered special attention.
Why AhR broccoli, Brussels sprouts, watercress and their ilk so important? For one, they contain indole compounds, which activate aryl hydrocarbon receptors in your gut’s immune cells–thus turning on a slew of health-promoting genes. AhR receptors may also play a role in inhibiting cancer stem cells–“the origins of cancer,” not destroyed by traditional therapies and a subject in need of much more scientific attention , Chapkin says.
- high fat diets, warned Chapkin; they promote inflammation.
- foods that cause rapid spikes in blood sugar, thus insulin– that is, sugars and refined carbs.
- And had longevity researcher Dr. Luigi Fontana been in attendance (my top personal pick for next year), he’d likely have added to the avoid list: high protein diets and foods rich in branched chain amino acids –in other words, animal foods once again. In a small clinical trial of overweight men, Fontana found that restricting protein alone to 7 to 9 percent of calories rapidly improved metabolic health. In just 43 days, it significantly decreased body fat and improved signs of insulin sensitivity. In Fontana’s rodent studies, restricting animal protein also significantly inhibited cancer growth. Why? Again, mTOR may the mechanism, he thinks.
3/ Eat less– and less often.
While the evidence is preliminary (that is, mainly in animals), UNC’s Dr. Stephen Hursting is excited about the metabolic changes that restricted dietary patterns may bring about–including patterns of Intermittent Fasting:
- 5-2 Diets: 5 days healthy Mediterranean, 2 days of limited calories (Some say 500 max), and
- Long overnight fasts: Restrict yourself to a window of eating—ideally within 8 hours. Every day? Does it matter what you eat otherwise? What if you fast for less than 16 hours? This study of breast cancer survivors found metabolic changes after just 13 hours of fasting. Nobody really knows for sure yet what the best parameters are.
In humans, intermittent fasting “can increase insulin sensitivity more than daily calorie restriction that achieves similar weight loss,” says Fontana. “Although preliminary, recent case studies in human patients suggest potential applications …in the treatment of a range of cancers.”
Putting it all Together: Hedge your Bets
It takes 15 years for good science to get out of the laboratory and into practice, say AICR scientists. I don’t know about you, but at 65, I don’t have time to wait.
As humans, we’re always making decisions based on imperfect evidence. We weigh the risks– both the likelihood and gravity of the consequences of choosing one path or another. For 15 years now, since the one and only recurrence of a slow growing cancer, I’ve been following the science of nutrigenomics (how nutrition changes the expression of genes), practicing the precautionary principle and choosing mainly plants.
Lupper’s now going on the menu. Dear family, After late lunch/early supper, I’m shutting down the kitchen in hopes of changing our metabolism and getting rid once and for all of what the cousins endearingly call “Sugar lumps.” Dear AICR, On behalf of the 3000+ followers of this blog, thanks for the heads-up.
About the author: Harriet Sugar Miller has been a freelance health journalist, cancer survivor and keeper of the family kitchen for three decades. She studied journalism and law in Blue Heaven and now lives in Montreal–or White Hell, depending on the season.