Day 117...Let's Talk About Metabolism

I have been meaning to get back to writing about nutrition, but just haven't been motivated enough to do so.  This morning however, I read an article that just might get me going on nutrition again.  This article was written, by Dr. Len Kravitz...no, not the singer!  Dr. Kravitz is well known within the health and fitness industry as a leader in physiological function, nutrition, and athletic performance.  He's kind of a big deal...just like me! :)

Anyway, you have read posts of mine in the past that referred to basal metabolic rate (BMR), and the importance of maintaining an elevated BMR when it comes to staying lean, or burning off unwanted fat.  There is however, some degree of controversy when it comes to metabolism.  Perform a google search for "Can you increase your metabolism" and you will a return of nearly 10,000,000...yep 10,000,000 results in only .14 seconds...now that's technology!  I glanced through the fist couple of pages, and found pretty close to a 50-50 split on whether or not one can truly increase their metabolism.  

Knowing if what you are reading is true or not can be CONFUSING!

Are you the type of person who likes to research stuff?  If so...what are you using to conduct your research?  The Internet has a wealth of information, yet much of it is considered anecdotal...meaning, there is really no sound research or evidence to support the idea or associated claims.  I would suggest using www.googlescholar.com  This site returns actual research studies...peer reviewed studies, that are evidence based.  Many of these studies have been published in industry journals, and have undergone heavy scrutinizing prior to publishing.  Now Dont get me wrong here...research is research...and research is often flawed, and sometimes inconclusive.  But trust me, pretty much anything that you find through a googlescholar search is dramatically better than what pops up on sites like wikipedia!

So what's the controversy?  Many people within the health and fitness industry feel that one's metabolism can be raised or lowered by manipulating food intake and exercise routines.  I have even referred to this concept in a number of my posts.  Here's the deal though...and it's something that I, and others in our industry take for granted (I believe).  Your metabolism is your metabolism.  It is commonly believed that you are born with your basal metabolic rate, and it is set by a number of genetic factors.  This is believed to be true.  Where the issue arises is when people say that we can actually change our basal metabolic rate.  Much of the evidence that exists however, does not support the claim of actually changing one's BMR.  Are you confused now?  Does it seem as though I may have told you mistruths? 

Let me explain...

Your metabolic level is pretty much set as a baseline...it's essentially what you were born with.  It is commonly thought that as we age, our metabolism slows.  What research suggests however, is that it our BMR is not really slowing...not by itself anyway.  What happens is that our BMR's become depressed...and I'm not talking about the kind of depression that we would take Prozac or other  anti-depressant medications for...I'm talking about the inadvertent reduction, below the normal baseline.  What causes this?  Poor nutritional habits, lack of exercise, and stress are the main reasons why our BMR can become depressed.  "But what about age?" you ask.  As people age, they tend to exercise less and develop poor eating habits, often relying heavily upon processed foods, thus consuming a higher number of calories daily, and ultimately creating a caloric surplus.  So you see, it's not that our metabolism changes as we get older...it's that we are causing it to become depressed...to work below it's normal operating range.  That's our fault...not our body's, and we shouldn't use age as a crutch to justify unhealthy weight gain.

Hang on a second...let me climb down off of my soapbox so we can get back to the article I mentioned earlier!

Okay, I'm down.  The article is titled "Metabolism Make-Over: Fact or Fiction?" and serves to answer common questions regarding resting metabolic rate and weight loss questions.  Resting Metabolic Rate or RMR, is very similar to Basal Metabolic Rate (BMR).  RMR is determined using slightly more stringent criteria, but for all practical purposes (at least those within this post!) is the same thing.  Within the article Dr. Kravitz answers seven questions...I have picked a couple of them to share with you here today.  

Question #1: How much does RMR decrease from diet-only interventions?

Alright...great question!  Before I share Dr. Kravitz' answer with all of you, let me set the stage for this question.  I have shared with you the dangers of diet-only interventions, and what can happen to our BMR when we decide to decrease our caloric intake too much at one time.  Dr. Kravits' answer not only sums up what I have share with you in the past, but places a number on just how severe this can be.  So here's the answer...

"Hill (2004) States that basal metabolic rate (BMR: very similar to RMR) can be suppressed up to 20% by energy restriction."  Kravitz goes on to say "However, Hill says that physical exercise (aerobic and resistance exercise) provides a protective effect against (a large reduction in calories).  RMR."

As you can see, this answer (and supporting evidence) supports what I have been preaching all along...that lean muscle mass must be preserved to accomplish healthy, sustainable weightloss.

I picked the following two questions to share with you based on the fact that I do not totally agree with what they are saying.  Remember...I said that research can be flawed...and it can be flawed in a number of ways.  I'll explain as we go.

Question #2: How Much does RMR change from continuous long-term participation in aerobic exercise?

This is a subject that draws much attention.  Over the years I have been preaching to my clients, family, friends...pretty much anyone who would listen...that resistance training is more effective than 'cardio' training at elevating one's BMR (and you all know now that what I mean by that, is actually re-elevating it out of a depressed state).  The reason for this?  The fact that the body tends to require longer periods of time to recover from resistance training than typical cardio workouts, and during that time, calories are being burned (fat calories) to support the recovery and regeneration process.  Here's the answer from Dr. Kravitz...which I really like due to the fact that once again he has put some hard-fast numbers to it...

"Potteiger and colleagues (2008) completed a 16-month study on the effect of RMR in adult female (exercising group=25, control group=18) and male (exercise group=16, control group=15) subjects who did aerobic exercise 3-5 days per week for 20-45 minutes per session at a moderate intensity (60-75% of their heart rate reserve)  There were mo RMR changes in the control group, who just maintained their normal exercise and diet patterns for the 16 months.  However, the females in the exercise group saw an average increase in RMR of 129 kcal per day (meaning they were burning and additional 129 kcal daily), while the males in the exercise group experienced an average increase in RMR of 174 kcal per day during this 16-month investigation."

So...as you can see, this study shows that individuals who participate in moderate-moderate intensity aerobic exercise can make a profound impact on re-elevating or maintaining normal BMR levels.  What is missing in here however, and what I would certainly like to see are the ages and starting RMR values for each of the study participants...especially in light of the answer to the next question.

Question #3:  How much does RMR change from continuous long-term participation in resistance training?

Alright...another great question!  Over the years, as I stated earlier, I have preached that resistance training will re-elevate one's BMR (RMR, REE, etc) more effectively than cardio training alone.  This was not simply an arbitrary decision, but based on evidence from a number of research studies, text book teachings, etc.  However, Dr. Kravits' answer to question #3 would lead one to believe that maybe this is no true...let's see.

"Hunter et al. (2000) conducted a 26-week resistance training study with beginning, sedentary and older (aged 61-77) males (n=7) and females (n=8).  Subjects completed supervised workouts consisting of 2 sets of 10 repetitions (with 2 minutes of rest between sets).  The resistance exercises were elbow flexion, elbow extension, lateral pull-down..."(and others).  The subjects trained at an intensity within 65-80% of their 1-repetition maximum (1RM).  Hunter and colleagues carefully integrated progressive overload into the program after reviewing daily training logs and after retesting 1RM every three weeks.  By the end of the 6-month investigation, male and female subjects had increased their RMR by 7%, which was approximately 100 additional kcal per day."

Okay...very interesting.  After reading questions/answers #2 and #3, one would believe that cardio training has a greater impact on elevating basal metabolic rates.  But wait...did any of you (who actually took the time to read what I just wrote) see anything that just didn't seem quite right?  Here's what I'm talking about...

First of all, in comparison to question #2, the subjects were elderly individuals whose basal metabolic rates were (quite possibly) severely depressed going into the study.  Second, there was no control group mentioned, meaning there was only one test group (separated into male and female groups)...not good.  Then...this study of 'long term effects' only took place over a period of 6-months, while the aerobic exercise study took place over 16-months...10-months longer!  So you see, when reading studies, one must critically evaluate the variables to determine whether or not the study provides valuable, relevant information.  Coupling these two studies in the same article was a poor choice in my opinion, as the results suggest that what is commonly believed to be true (evidence-based) might be wrong.  When these situations arise, authors must strive to use studies and investigations that use equal measures against both hypotheses, to obtain accurate results.

I hope I didn't put too many of you to sleep with this post!  I just thought some of you might be interested in it.  Thanks for following!