Breast cancer is a disease every woman should be concerned about. According to statistics, one in seven will develop this disease at some point over a lifetime. One risk factor for post-menopausal breast cancer is being overweight or obese. In fact, obesity increases the risk of a number of types of cancer, including cancer of the pancreas, esophagus, colon, rectum, uterus, kidney, thyroid, and gallbladder. In women, up to 7% of cancers, in general, can be blamed on obesity. Yet, at least in terms of breast cancer risk, metabolic health, that is normally associated with obesity, may be spurring the growth of breast cancer.
Breast Cancer, Obesity, and Metabolic Health
One of the most common health problems women who are overweight or obese have to deal with is insulin resistance. What is insulin resistance? It’s a condition where cells don’t respond as well to the insulin your pancreas produces. As you know, insulin is the “key” that unlocks the door of a cell to let the nutrients you take in through diet in.
After you eat a meal, your insulin level rises transiently. You need a certain amount of insulin to get glucose and amino acids into cells but you don’t want a high insulin level all the time. Yet, that’s exactly what happens to people with insulin resistance. They have to produce more insulin to get the doors to cells to open up. This is what we call insulin resistance.
Metabolically Healthy Obesity
A significant number of people who are obese are also insulin resistant – but not all. As many as a quarter of obese men and women are metabolically healthy, meaning they aren’t insulin resistant and don’t suffer from the conditions associated with it, like high blood pressure and elevated lipids. Unfortunately, a number of the metabolically healthy obese will, over time, go on to acquire these health problems.
What does this have to do with breast cancer risk? According to a study carried out at Imperial College London School of Public Health in England, metabolic health is a more powerful determinant of post-menopausal breast cancer risk than body weight. Could it be that excess weight per se isn’t driving breast cancer but the insulin resistance that goes along with it?
To explore this hypothesis, Dr. Marc Gunter, and his colleagues at Imperial College London School of Public Health followed 3,300 women over eight years. They looked at factors like their fasting insulin level, degree of insulin resistance, and their body weight. Surprisingly, what they found was overweight and obese women who had normal insulin levels and weren’t insulin resistance were NOT at higher risk of breast cancer, whereas normal-weight women with high insulin and insulin resistance WERE. In fact, having a high insulin level was linked with double the risk of developing breast cancer, irrespective of weight.
Although more research is needed, this suggests is breast cancer risk may depend more on how metabolically healthy you are rather than how much you weigh. Further support for this idea are studies showing women with type 2 diabetes have a higher risk of some forms of cancer, including breast cancer. Most people with type 2 diabetes are also insulin resistant.
How Might Insulin Resistance Increase Breast Cancer Risk?
Although the exact way insulin promotes breast cancer isn’t completely understood, we know that insulin is a growth factor and one that can spur the development of tumor cells. In fact, breast cancer cells have receptors for insulin on them. Insulin also exerts its growth activity through another insulin-like factor called IGF-1.
Another way insulin may promote breast tumor growth is by its effect on estrogen. As you know, estrogen is a female sex hormone that has benefits but can also stimulate breast cancer cells to grow. You need a certain amount of estrogen but too much and you overstimulate breast cells and increase the risk of a cancer-causing mutation. Your liver produces proteins that bind to estrogen and inactivate it. Having more of these estrogen binding proteins means less free estrogen is available to stimulate breast tissue. When you have a high insulin level, you have fewer estrogen binding proteins. Therefore, there’s more free estrogen to over-activate breast tissue.
Metabolic Health: Signs that You May Be Insulin Resistance
If you’re insulin resistance, you want to know it. Here are some signs that suggest you’re not metabolically healthy and suffer from some degree of insulin resistance:
. You’re overweight
. You’re over the age of 40
. You have high or borderline high blood sugars
. You have high blood pressure
. Your lipids are abnormal (high triglycerides, low HDL)
. You have a waist size greater than 35 inches
. You have a history of polycystic ovary disease
. You don’t exercise regularly
Metabolic Health: Improving Insulin Resistance
Some things you can do to reduce insulin resistance and lower your risk of breast cancer:
Exercise – Both aerobic and resistance training are two of the best ways to decrease insulin resistance.
Maintain a healthy body weight – Insulin resistance is more of a problem in people who are overweight or obese.
Eliminate refined carbohydrates & sugar from your diet: Both cause a rapid rise in blood sugar that worsens insulin resistance.
Sleep at least 7 hours a night.
The Bottom Line
Obesity and insulin resistance are common but it may be insulin resistance that’s the greatest threat for developing breast cancer. Fortunately, the lifestyle you lead can impact how your body handles insulin and glucose. Even if you’re of normal weight, your risk of breast cancer may be higher due to a high insulin level. Make sure you’re not fueling the flames of insulin resistance with a bad diet, inadequate sleep, and lack of exercise.
WebMD. “Unhealthy Insulin Levels May Up Breast Cancer Risk”
National Cancer Institute. “Obesity and Cancer Risk”
Experimental Diabetes Research Volume 2012 (2012), Article ID 789174, 12 pages.
Science Daily. “Assessing insulin resistance can inform about breast cancer risk”
Journal of Experimental & Clinical Cancer Research, 2013; 32 (1): 14 DOI: 10.1186/1756-9966-32-14
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