Exploring the Interplay Between Cancer Risk, Physical Activity, and Obesity: Unveiling the Pathways to Prevention

In an era where health consciousness is gaining paramount importance, the relationship between cancer risk, physical activity, and obesity has emerged as a significant area of investigation. As you and I – and many of our friends –  are impacted by this scary disease, understanding the intricate connections between these factors can reduce our fears.  Spoiler alert, you have way more control at reducing your chances of developing cancer than you may think.

This article will take you on a fascinating journey of how a healthy cell becomes a cancer cell, and shine a light on how physical activity and obesity intertwine to shape our vulnerability to this devastating disease. By unraveling the underlying mechanisms, we aim to empower you with the knowledge needed to reduce cancer risk and foster a healthier, happier future.

Cancer Statistics In the US

In 2020 there were 1.8 million new cases of cancer in the US and 600,000 will die from the disease. 43% of cancer in men is from prostate, lung, and colorectal.  50% in women are from breast, lung, and colorectal. But there is good news. 30-40% of cancers are potentially preventable. So, given these somewhat scary statistics, lets go a little deeper into what cancer is, how it develops and how it spreads.

What is cancer and how does it develop

Our bodies are made up of trillions of little cells. Within each cell is a nucleus that contains genes that serve as an instruction manual for that cell. The genes tell a cell when to grow, work, divide, and die. A gene is made up of strands of DNA. DNA is like the OG of each individual human. It was the instruction manual assigned to you in the womb.

When our DNA is working properly, it tells a cell when to divide and become 2 cells. This is how normal tissue grows. One cell divides and becomes two. Those two cells divide and become four and so on.

But genes can become damaged and mutate. When this happens, a cell can turn from a normal cell into a cancer cell. Cancer cells have mutated genes that don’t function properly. Cancer cells grow and divide uncontrollably. When this happens, they start to take up space, “pushing out” normal, healthy cells. At this point, Houston we have a problem. Now, malfunctioning cancer cells start growing into organ systems and effecting the entire organs from functioning properly.

There are Inherited gene mutation and Acquired Gene mutations. Acquired gene mutations are not inherited from a parent and occur throughout life. Acquired mutations occur in one cell and are passed on to another cell.

How do genes effect cancer?

Some genes are responsible for controlling when a cell grows, divides (turning 1 cell into cells), dies and repair damaged DNA. Oncogenes make sure cells divide. Tumor suppressor genes make sure cells die at the appropriate time, and DNA repair genes repair damaged genes. Changes to these genes can cause a cell to divide uncontrollably, outlive their appropriate “life-span”, or lead to a build up of “DNA changes”.

What causes genes to mutate and turn into cancer cells?

There are still a lot of unknowns in cancer research. However, there is some consensus that gene mutation can be inherited or they can develop as we age via the genes “wearing out”. Genes may also become damaged as a result of exposure to cigarette smoke, alchohol, or unltraviolet light. But there is another condition that causes genes to mutate, inflammation.

Role of Inflammation In Cancer Development

Inflammation is critical in that it protects humans from disease, bacteria, viruses, infections, and promote tissue repair. Simplified, when an injury occurs or a foreign invader enters the body, the cells in the area release pro-inflammatory cytokines that trigger the immune system to deploy immune cells from the lymph nodes.  These immune cells travel in the blood to the area, remove the foreign invader, clean up any dead or damaged cells, and start the repair process (in the case of an injury). Oh, and most importantly, the immune cells leave the area via the release of anti-inflammatory cytokines. Put a pin in the term “anti-inflammatory cytokines” because that will be important in a little bit.

There are two types of inflammation. There is acute inflammation and chronic inflammation. If the immune cells do not leave the area, or for some reason there is an imbalance between the pro-inflammatory mechanisms and the anti-inflammatory mechanisms, immune cells will stick around and lead to chronic inflammation, autoimmunity, and tissue damage.

Chronic inflammation has been linked to several diseases including atherosclerosis, myocardial infarction (heart attack), heart failure, Parkinson’s disease, Alzheimer’s disease, asthma, diabetes, arthritis, psoriasis, osteoporosis, and yes, cancer.

Some reports suggest that potentially 25% of cancers are linked to chronic inflammation. For example, irritable bowel disease (an inflammatory disease of the colon) is believed to be a risk factor for developing colorectal cancer.

Connecting the Dots

So, to be clear, acute inflammation is necessary for humans to survive. On the other hand, chronic inflammation is no longer protective and damages healthy tissues. Obesity creates an environment of chronic systemic inflammation and is believed to be a major risk factor for developing cancer.

How does obesity cause cancer?

Although the mechanisms are still somewhat unclear, most believe obesity triggers a multistage process that causes damage to DNA. And as stated above, damaged DNA (mutated genes) turns normal cells into cancer cells. One accepted hypothesis is that excess adipose tissue (made up of fat cells) release pro-inflammatory cytokines which in turn creates chronic systemic inflammation.

Adipose tissue also promotes the release of a hormone called leptin. Leptin is a hormone that tells the brain we are full. Basically, all the “storage sheds” are full so please stop sending in more “supply”. In addition to telling the brain we are full, leptin also gives us energy. To “burn down that excess supply”. However, too much of a good thing is a real phenomenon.  And is the case when it comes to leptin. Too much circulating leptin causes the reverse to happen. The body will become less sensitive to the leptin and the brain stops getting the “full” signal and the body is told to sit still (decrease activity level) to conserve energy.  Furthermore, excess leptin in the blood promotes systemic inflammation

Insulin resistance and increased cancer risk

Poor glucose metabolism is also known to increase risk of certain cancers and is associated with excess adiposity (excess fat cells). This has to do with the way that the body manages glucose (sugar). Sugar in the blood triggers the pancreas to release insulin which helps to drive glucose into the cells of the body (where it is converted into energy.) If blood sugar levels remain high, over time, the cells become less sensitive to the insulin and so the body starts producing more insulin. This causes excess insulin in the blood and is called hyperinsulinemia. Hyperinsulinemia shows some evidence that it promotes tumor growth.

What is the best way to reduce risk of cancer?

The good news is that there is emerging evidence that the BEST way to reduce risk of cancer is to increase physical activity. And no, not only because it might decrease obesity. It is much more exciting than that. Physical activity triggers a whole host of biological mechanisms that actually protect DNA and prevent cancer development and growth.

How will physical activity decrease risk of cancer?

Ok, so this is how it works. Exercise initially causes the release of pro-inflammatory cytokines discussed above. This increase in pro-inflammatory cytokines stimulated the release of anti-inflammatory cytokines. So, in essence, exercise causes a little bit of stress and the body learns how to be better at responding. You can learn more about this idea of “good stress” in our article on hormesis.

Physical activity also promotes blood glucose metabolism (process of turning glucose into energy). Regular physical activity increases the body’s need for energy (glucose).  When energy demand increases, more glucose is metabolized via taking glucose from the blood and into the cells. This requires insulin. This drives down the amount of insulin in the blood which makes are cells more “insulin sensitive”.  Imiproved insulin sensitivity allows the body to become more efficient metabolizing glucose.  And here we have a beautiful positive feedback loop.

And the most obvious benefit of physical activity is on adiposity (fat cells).  Here is how it works… physical activity causes increased energy damand. When energy demand goes up, the body will take more glucose from the blood and push it into the cells.  This lowers the blood glucose. When energy demand is high and blood glucose levels drop, the body converts stored glucose in the fat cells to energy. The result is decreased adipose tissue (fat cells).

How much physical activity is required to decrease cancer risk?

First lets define the different categories of physical activity. You are considered “physically active” if you are performing 30 min of moderate intensity activity 5-7 days/week. Moderate intensity means that your heart rate is increased but you could still carry on a conversation. If you sit six or more hours during your waking hours, you are considered sedentary.

Now, if you are in the sedentary group, I have good news. There is something called a dose-response curve.  Simplified, what this means is that if you are currently sedentary and you start standing more and adding as little as a 10 min walk to your day, all measures of health improve. So, don’t get overwhelmed or think about that daunting “30 min/day”….yet. Just start.

If you are someone who goes to the gym in the morning and get in your 30 minutes and then go to the office and sit for 8 hours, technically, you might fall into the “sedentary group”. If this is the case, there is potential to do a little more. If you are in this category there are ways to increase your activity level:

• Go for a short walk on your lunch break
• Follow the 20/20/20 rule. Every 20 minutes looks out away from your screen and stand for 20 sec
• Park in the furthest parking stop from our office door.
• Whenever possible, take the stairs
• Go for a short walk after each meal. Primarily dinner as it has been shown to improve glucose metabolism to do this before going to bed.

Conclusion

Not to be “doom and gloom”, but when it comes to the “C word”, it is not if, but when. When will you be directly or indirectly impacted by this terrifying word, cancer. Now, I don’t tell you this to scare you. I tell you this because it is the reality. For as long as I can remember, we have all been made to assume that it was “genetic”. Or that people who developed cancer were exposed to a “carcinogen”. And yes, this may be true. But hopefully now you are aware that you have the power to decrease your risk and improve your life. It costs nothing, doesn’t require any special supplement, and can be done anywhere at any time. Movement truly is medicine.