Duration and intensity matter

AN ARTICLE FROM CNN.com by Jacqueline Howard “How Much a Decade of Obesity Increases Your Risk of Cancer” brings attention to a study examining the long-term health dangers to women carrying excess pounds. Roughly 70% US adults are overweight and 36% are obese, making the condition an important public health concern.
 
Melina Arnold, a scientist at the World Health Organization's International Agency for Research on Cancer was lead author of the study, “Duration of Adulthood Overweight, Obesity and Cancer Risk in the Women’s Health Initiative: A Longitudinal Study from the United States”, published in PLOS Medicine on August 16, 2016.
 
The study followed nearly 74,000 postmenopausal women, recruited at ages 50-79 years from late 1993 to late 1998, over a mean of 12.6 years. Approximately 60% were overweight or obese as adults. 6,301 invasive obesity-related cancers were recorded during the study. Obesity-related cancers were identified as those in which previously there was “convincing evidence of a positive relation to excess BMI*: colon, rectum, liver, gallbladder, pancreas, postmenopausal breast, endometrium, ovary, kidney, and thyroid”.
 
Overweight status was defined as BMI ≥ 25 kg/m2, and obese as BMI ≥ 30 kg/m2. Statistical modeling was used to analyze the self-reported BMI obtained from study subjects at baseline ages 18, 35, and 50 years (the information was retrospectively recalled), and from “weight and height measurements at baseline and at 3-year follow-up, and from self-reports at follow-up years 4–8”.
 
For every decade of being overweight the study found an overall increase of about 7% of all obesity-related cancers. “After adjusting for the intensity of overweight (that is, how overweight individuals were), these figures rose to 8% for postmenopausal breast cancer and 37% for endometrial cancer”.
 
The average duration of being overweight was 31.3 years and of being obese was 20.6 years. Overweight or obese women were slightly younger at baseline age, “had a lower education and were more likely to be African-American”. They tended to be less physically active, have higher calorie but poorer quality diets, and report being diabetic.
 
In the CNN article a point is made that additional questions have been raised about overweight, obesity, and cancer risk by this study. For example, the authors now wish to know if the age of overweight onset matters, specifically if onset occurs in childhood or at a younger rather than an older adult age.
 
The last section of the scientific paper identifies what these findings mean. The researchers conclude, ”how much of their adult lives women are overweight and how overweight they are play important roles in cancer risk. This finding highlights the importance of obesity prevention at ALL AGES and from EARLY ONSET” (capitals letters added by me).
 
What do the findings mean for running? Simply focusing on calorie restriction to achieve weight loss as a healthy life goal can be disheartening for women or men.  Setting running or walking competition goals, and then following a training plan and adopting a sport-friendly nutritious diet can transform the passive, negative ‘subtraction’ mindset of dieting into the active, positive exhilaration of ‘addition’ as the dieter becomes the athlete.

I think this type of cycle (run… train… compete… repeat) is more likely to help individuals sustain a SAFER body weight over a lifetime than loss-and-gain, yo-yo dieting. The study showed that the INTENSITY of overweight increased cancer risks with time. This means that merely weighing LESS, even if not within the ideal BMI range, carries LESS cancer risk. Thus, working toward this more reasonable outcome can be a worthwhile effort that might be aided by the addition of competitive sport activity.
 
Encouraging children and adolescents to engage in competitive sport activities may significantly delay the onset of overweight and obesity in adulthood. Barriers to participation like equipment cost, venue availability, and skill acquisition are relatively low in running/walking compared with other sports. Opportunities to compete are nearly endless, especially with free Earned Runs bib (shameless plug) at any age. Family participation in the same races is easily arranged; inclusion of siblings, neighbors, and schoolmates almost automatically engenders friendly rivalries.

Current runners and walkers might look outside themselves, invite hesitant onlookers of either gender to join in the fun, and shepherd them along the way!

*BMI= Body Mass Index
 
RUN HAPPY!
 
http://www.cnn.com/2016/08/16/health/obesity-overweight-cancer-risk/index.html
 
http://journals.plos.org/plosmedicine/article?id=info:doi/10.1371/journal.pmed.1002081