Time and Weight

I recently attended the two-day fall meeting of the New England Chapter of the American College of Sports Medicine in Springfield, Mass. The sessions included a range of topics with this year’s theme focusing on the connection between exercise and mental health. I attended one session entitled “The Dirty Side of Clean Eating.”  The two presenters were registered dietitians who drew from what they observe in their client base. Among other things, they parsed the difference between eating disorders and disordered eating.  They noted while 9% of the population will experience an eating disorder during their lifetime well over 50% show signs of disordered eating, which may include chronic dieting, food restriction, categorically avoiding certain foods, as well as constant scale and mirror watching.  An eating disorder can be fatal as well as lead to the dreaded “female athletic triad,” a combination of osteoporosis, low energy, and amenorrhea with the men’s version resulting in the first two, whereas disordered eating affects quality of life and detracts from optimal health.

Diet and weight are touchy, related topics.  They involve preferences, knowledge, beliefs, and biases, all of which are fed by various sources of information, some of which are contradictory.  While runners intuitively know that carrying extra weight slows us down,  becoming obsessed with our weight and body image can lead to the dark places noted above. 

Runners of all ages aim to maintain a “healthy” weight while taking in sufficient nutritional quality and quantity to support vigorous training.  This becomes one’s set point weight, which varies depending on body type, muscular definition, and genetic bone structure. These factors make assigning a target BMI (body mass index) problematic.  BMI is the measure the National Institutes of Health uses to indicate 73% or the U.S. population is overweight or obese.  Most runners fall well below this threshold.   

For seniors, establishing a set point weight is complicated by the fact our bones and muscle are being slowly replaced by fat.  This is not the stuff we can pinch.  Rather, it becomes entwined in our muscles.  There are two issues here: One, since muscle uses more energy than fat, our basal metabolic rate (BMR) decreases.  Thus, if we eat the same amount of food as we did when we were 40 we will gain weight, even when keeping physical activity constant.  Two, muscle and bone weigh more than fat. Thus, if we are the same weight as 20 years ago, we have more fat and less lean tissue.  The result is by age 60, and likely before, the set point that depicts a healthy weight typically decreases due to this loss of muscle and bone. Ideally, we weight train to retard muscle loss, but it invariably happens regardless. Thus, it behooves us to periodically track our weight and watch what we eat. It is easier (and far better for our bodies) to maintain weight rather than cyclically gain and lose.  

So, what is the cost of this so-called “extra weight” when we race? Studies have shown that each pound over one’s set point weight costs a runner, on average, two seconds per mile.  For 10 extra pounds that translates to about two minutes in a 10K and over four minutes in a half marathon. For a serious recreational runner that is a significant time difference.  

As with most things in life (and running!) finding proper balance is important. We should rightly pay attention to our weight and body definition while not obsessing over them. For sure, there are various ways aging impacts race times.  That can be daunting, but it may also offer us a puzzle to be continually explored.