Can Being Overweight and Sedentary Increase Your Risk of Cancer?

Excess body weight (EBW) is a problem of our time and society. Almost nonexistent 100 years ago, excessive body weight now affects over 2 billion adults and 340 million children worldwide². Worst yet, this global health problem of overweight and obesity is expected to double in the next 10 years². This rise in EBW worldwide “is thought to be driven largely by changes in the global food system, which promotes energy-dense, nutrient-poor foods, alongside reduced opportunities for physical activity³.”

EBW in adults can be defined as a body mass index (BMI) ≥ 25 kg/m2. It is also defined as abnormal or excessive fat accumulation and is associated closely with two other weight-related conditions – overweight (BMI of 25.0–29.9 kg/m2) and obesity (BMI ≥ 30 kg/m2)². These can be attributed mainly to two other lifestyle factors – sedentary behavior (and physical inactivity) and unhealthy diets².

Now let’s look at some dates and associated EBW percentages³:

1975

• EBW in men 21%
• EBW in women 24

2016

• EBW in both sexes 40%

Health Conditions Linked to Excess Body Weight and Cancer Risk

The rate of EBW almost doubled both for men and women in the last 40 years. And in the case of obesity, which is even more concerning, the numbers quadrupled in men, from 3% to 12%, and more than doubled in women, from 7% to 16%³.

EBW has been associated with various health conditions²:

• Type 2 diabetes mellitus
• Non-alcoholic fatty liver disease
• Cardiovascular disease
• Certain cancers, particularly colorectal cancer

This global increase in EBW is problematic because with this rise the “global cancer burden attributable to this condition is likely to increase in the future³.” This means that the number of cancer cases and cancer deaths associated with EBW will increase in the upcoming years and decades.

As we mentioned before, EBW is highly correlated with two other lifestyle factors we want to address: sedentary behavior and/ or physical inactivity, and unhealthy eating habits.

How Physical Inactivity Increases Cancer Risk

Gyms are a thing of our era, as is physical inactivity. Before the Industrial Revolution, moving and having jobs that required being physically active was the norm. However, as machines replaced human jobs, workplaces changed, and technology evolved, our need to perform physically demanding tasks decreased.

Understanding Physical Inactivity and Its Impact on Health

Physical inactivity differs from sedentary behavior, although both are detrimental to health. To bring clarification, let’s look at the definition of those two terms, and others related to movement or lack thereof.

• Physical activity – Any body movement generated by the contraction of skeletal muscles that raises energy expenditure above resting metabolic rate. It is characterized by its modality, frequency, intensity, duration, and context of practice^4,5.
• Physical inactivity – Represents the non-achievement of physical activity guidelines⁴.
• Exercise – Subcategory of physical activity that is planned, structured, repetitive, and that favors physical fitness maintenance or development^4,5.
• Sport – Sport is part of the physical activity spectrum and corresponds to any institutionalized and organized practice, reined over specific rules⁴.
• Sedentary behaviors – Any waking behaviors characterized by an energy expenditure ≤ 1.5 METs, while in a sitting, reclining, or lying posture^4,6.

The Health Impact of Sedentary Behavior and Cancer Risk

Most of us have become sedentary, spending much of our day sitting and not engaging in physically challenging activities, or even walking much.  A study evaluating “Sedentary Behaviors and Biomarkers Among Breast Cancer Survivors” reported that the average time the participants spent sedentary per day was 499 minutes and the average time spent standing per day was 248 minutes⁷. That is more than eight hours of sedentary time per day (low energy expenditure), and a little more than four hours spent standing. The authors of this study concluded that something as simple as increasing the number of daily sit-to-stand transitions (getting up from your chair and sitting back down) can be a valuable intervention to improve health biomarkers, mainly by reducing fasting insulin and insulin resistance⁷.

An analysis of the relationship between sedentary time and cancer mortality

In a study of 8002 adults published in 2020, researchers found that more sedentary time was associated with a higher risk of cancer mortality, while “replacing sedentary time with light- or moderate- to vigorous-intensity physical activity was associated with reduced cancer mortality risk⁸.” The authors support the message “that adults should sit less and move more to promote health and longevity⁸.” Another study found that interrupting prolonged sitting time with short bouts of standing significantly reduced postprandial (after a meal) glucose⁹. Light-intensity walking was even better than just standing, showing a greater reduction in both glucose and insulin when compared to standing interruptions and prolonged sitting⁹.

Why Sitting Less and Moving More Reduces Cancer Risk

All these studies are telling us to sit less, get up often, and move more. This will improve several biomarkers of health, like glucose and insulin regulation, reducing the risk of chronic conditions and cancer and improving overall health.

Besides being sedentary, most people do not meet the daily or weekly recommended physical activity guidelines, hence they are physically inactive. It’s easy to understand how not moving enough, whether through spending our day in sedentary behaviors (not moving much, which can happen sitting, lying down, or standing) or through not engaging in regular physical activity, has become a major health concern.

Are You Meeting Physical Activity Guidelines?

Data from the “National Health Interview Survey” shows that in 2020, only 24.2% of adults aged 18 and over met the “2018 Physical Activity Guidelines for Americans” for both aerobic and muscle-strengthening activities¹⁰. This means less than a quarter of the US population meets the recommended guidelines. The guidelines for adults include¹¹:

• At least 150 minutes to 300 minutes a week of moderate-intensity, or 75 minutes to 150 minutes a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity aerobic activity.
• Muscle-strengthening activities on 2 or more days a week. 

The authors point out that about 80% of US adults and adolescents (yes, the problem extends to adolescents) are insufficiently active, highlighting the importance of physical activity to foster “normal growth and development,” “make people feel, function, and sleep better and reduce risk of many chronic diseases¹¹.”

How Physical Inactivity Contributes to Cancer Risk and Mortality

As a quick reminder, physical inactivity is associated with 2.9% of all cancer cases and 2.5% of all cancer deaths¹, and many studies show that being physically active is a key lifestyle factor associated with reductions in both the risk of incident cancer and the risk of death from cancer^1,12,13.

The good news is it’s never too late to start.

The results of the “American College of Sports Medicine Roundtable Report on Physical Activity, Sedentary Behavior, and Cancer Prevention and Control¹⁵” show that:

• Physical activity is beneficial for the prevention of several different types of cancer.
• Decreasing time spent sedentary may also lower the risk of certain cancers.
• Physical activity pre- and post-diagnosis is beneficial for survival outcomes of certain types of cancer.
• Post-diagnosis physical activity seems to exert a greater effect on cancer outcomes when compared with pre-diagnosis physical activity.
• Physical activity was associated with an increased risk of melanoma highlighting the importance of sun safety while engaging in physical activities outdoors.

How Physical Activity Impacts Cancer Prevention and Survival

The authors state that “collectively, there is consistent, compelling evidence that physical activity plays a role in preventing many types of cancer and for improving longevity among cancer survivors¹⁵” and that “being physically active is one of the most important steps people of all ages and abilities can take for cancer prevention, treatment, and control¹⁵.” This study revealed that physical activity is beneficial even after a cancer diagnosis and even more effective, which means it’s never too late to start. But you do need to start.

Easy Tips to Increase Physical Activity and Lower Cancer Risk