Last Monday, while helping my friend Chef Leslie McKenna host the opening evening of her “Food for Thought” conscious cooking series, I was surprised to learn how little is understood about one’s metabolism.

A woman asked me how age was affecting her body and making her gain weight. Another woman from the class, we’ll call her Jane, fielded the question. Jane, in her late 60’s, said something to the effect of, “I’ll tell you what happens, your metabolism doesn’t just slow down, it STOPS.”

I recall looking at the other members of the class, mostly women in their late 30’s to early 50’s, their faces were a mix of shock and dismay. I on the other hand, was doing all I could to keep from running across the room, hurdling my body over the tables, screaming out “Noooooooooo,” while tackling Jane to the ground. Clearly this was not an option.

I took a breath, looked at Jane, and replied, “I’m going to respectfully disagree.” I looked at the class and tried to be direct and clear as I continued, “While there are many changes that happen in your body as you age, particularly hormonal changes, I do not believe that they are the leading contributor to weight gain. It’s easy to blame a slowing metabolism to ‘age’ but like anything else, we must take responsibility for our own actions.”

I went on to explain that in general, as we get older, our lives change, we take on more responsibility. We take on demanding jobs, we build a family, we eat out more often and get less sleep. Consequently, as our lifestyle changes so does our activity level. It is not uncommon for one to find themselves with less free time and less free time often leads to less physical activity which yields a decrease in caloric expenditure during your day. Moreover, less physical activity inevitably leads to a loss of muscle mass in the body, which again means, fewer calories burned during the day because your MUSCLE fuels your metabolism.

Now, before I go further, let me express that what we commonly refer to as our “metabolism” is more accurately referred to our Resting Metabolic Rate (RMR). RMR refers to the amount of energy (calories) that is burned in a day while at rest. The amount of activity that you perform throughout the day is added to you RMR to yield a total caloric expenditure.

To find out what your RMR is, follow the Cunningham formula: RMR = 500 + (22 x LBM kg) with LBM meaning Lean Body Mass. 

Let’s take two women, both who weigh 150 lbs. Abby has 20% body fat while Zoe has 30% body fat. This is how the formula’s work:

Abby
Body fat mass 150 x 0.2 = 30 lbs
Lean Body Mass 150 – 30 = 120 lbs
LBM (kg) 120 lbs / 2.2 = 54.54 kg
Cunningham 500 + (22 x 54.54) = 1700

Zoe
Body fat mass 150 x 0.3 = 45 lbs
Lean Body Mass 150 – 45 = 105 lbs
LBM (kg) 105 / 2.2 = 47.73 kg
Cunningham 500 + (22 x 47.73) = 1550

SO, according to these calculations, Abby burns 150 calories more everyday than Zoe if they’re both just sitting at home on the couch watching movies. That’s an extra 4200 calories burned a month! If we add light activity to this equation, say walking the dog 2x a day, we find:

Abby:  1700 x 1.5 = 2550                 
 Zoe:  1550 x 1.5 = 2325

This means that by simply walking the same distance, in the same amount of time, Abby burns an additional 225 calories a day because she has more lean body mass, even though they weigh the same.

I use this to illustrate the importance of physical activity. It is important to not only do perform physical activity that elevates our heart rate but also activity challenges our physical strength, so that we can retain and build muscle. Muscle cells require energy (calories) in order to be sustained where fat cells, essentially do not. The greater muscle mass we have the greater our “metabolism”.

To put it plainly: ↓ physical activity = ↓ muscle mass = ↓ RMR

Though I am not disregarding the myriad of hormonal changes that happen within our body as we grow older, I am advocating a choice to be pro-active. We generally have control over how we choose to adapt to changes in our body. Being physically active has greater rewards than just keeping up fit — it elevates our moods, reduces our stress and improves the quality of sleep. We just have to choose to be proactive instead of surrendering or giving into the false belief that we are doomed because our metabolism has stopped.

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CHRISTA PRYOR – Not only a college athlete with a degree in Kinesiology and a Masters in Human Movement, Christa was one of the youngest division 1 Head Strength and Conditioning Coaches in the country. She has trained athletes from diverse sports and skill levels; including the NBA, MLS, and AAA baseball. Christa has contributed to multiple fitness magazines including Fitness Magazine, and been profiled on local news channels highlighting her innovative training methods. Her latest passion is working with Play for Her and Pryor Performance, two non-profit organizations sharing a common objective, to bring strength and conditioning programs to underrepresented young athletes.