Exercise Prescriptions - How They May Differ In Obesity

In follow up from my recent blog on the Home VO2max text, let's now talk about resting VO2, which is the amount of oxygen we consume at rest per kilogram of body weight per minute, and therefore a measure of basal (resting) metabolism.  This blog post is a little heavy in the math details, but trust me, well worth it to understand for anyone who struggles with their weight, and for any health care professional who cares for people with obesity. Read on!

There are many things that affect resting VO2, including:

• Age (resting VO2 decreases with age)
• lean body mass (resting VO2 is higher with more muscle) 
• higher Body Mass Index (BMI) - resting VO2 decreases with higher BMI.  In other words, people with obesity may have a lower resting VO2, and this gets lower with more excess body weight.  This is due to a number of factors, including genetics, sympathetic nervous system tone, and also because fat tissue is less metabolically active per kg.

The amount of oxygen we consume at rest is equal to one MET (metabolic equivalent) of energy. The amount of oxygen used and energy burned (Calories or kcal) at rest is generally assumed as follows:

Resting VO2 = 1 MET = 3.5 mL/kg/min of oxygen

1 MET = 1 kcal/kg/hour of energy burn

We often describe physical activity in METs:

• Light activity: less than 3 METs
• Moderate activity: 3-6 METs
• Vigorous activity: 6 METs or more

For example: 

• walking at 4 miles per hour is about 3-5 METs (moderate activity)
• shovelling dirt or light snow is 5-7 METs
• jogging at 5mph is about 7-9 METs
• shovelling heavy snow or playing squash is 9 METs or more

A full compendium of METs with particular physical activities can be found here.

Key Point: For some people with obesity, because they may have a lower resting VO2 and therefore a lower resting MET, 'moderate activity' of walking at 4 mph may actually be well into the vigorous METs category for them.

To assign a person with obesity who has a much lower resting VO2 a 'standard' moderate exercise prescription may result in this person feeling heavy exertion at that level of intensity - a potentially unsafe leap in exertional intensity, and also leaving one feeling discouraged that the activity feels too intense to continue.

Therefore, attention health care professionals:  When helping a patient with creation of an exercise prescription, it is important to listen to your patient (as always!), and understand what kind of activity gives them what level of perceived exertion - you may need to start the exercise prescription for your patient with weight struggles at a lower level of activity.   Most exercise prescriptions start with a moderate level of exertion, so for example, if walking at 2mph gives your patient a sense of moderate exertion, this would be where the exercise prescription would start, and you and your patient can build upwards from there.

If you are personally thinking about embarking on an exercise program, be sure to speak with your health care professional to see if any health checks need to be done before you begin.  When you and your health care professional are ready for you to begin, use this awesome METs compendium to find something fun - the choices are endless!

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www.drsue.ca © 2015 

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How Fit Am I? The Home VO2 Max Test

Ever wonder how fit you are, or if this could be measured?  The best measure of aerobic fitness is called the 'VO2max', and is literally equal to the volume of oxygen consumed per minute during maximum exercise effort.

How does VO2max reflect fitness?  Well, we use oxygen to generate energy (called ATP) at rest and during aerobic activity.  Energy can be generated without oxygen for very short periods of time, which is called anaerobic respiration, but the best marker of endurance/cardiorespiratory fitness (which requires oxygen) is the maximum possible oxygen consumption that a particular person can achieve - that is, the VO2max.

The VO2max is most accurately measured in a lab, where oxygen consumption is measured while a person exercises to maximum capacity on a treadmill or stationary bike.

There are a couple of neat ways that VO2max can be predicted: (IMPORTANT: check with your doctor to make sure it's safe for you to do these tests before you proceed)

• the 1 mile walk test
• the 3 minute step test

VO2max ranges and what they mean for fitness level can be found here.

To learn about VO2 at rest, how this translates into METs, how this is important for exercise prescriptions, and how this can be different in people with obesity... stay tuned to www.drsue.ca for more!

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www.drsue.ca © 2015 

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Secrets To Success - Keeping Weight Off

Have you ever wondered what the secret to success might be, for people who have lost weight and have been able to keep it off?

While the answer to this question will be different for each individual, the American National Weight Control Registry was established in 1994 to try to identify behaviors associated with long term weight loss success.   It is the largest prospective observational study of weight maintenance out there, and includes individuals who have maintained a weight loss of at least 30 lbs for at least 1 year.

Some interesting facts about NWCR members:

• 80% are women, 20% men
• average age is 45-50 years
• 45% lost weight on their own, and 55% with a program

Here are the winning patterns of NWCR members:

• 98% modify their food intake in some permanent way: portion control, low fat diet
• 90% exercise at least 1 hour per day, burning at least 400 calories per session
• 78% eat breakfast every day
• 75% weigh themselves once a week
• 62% watch less than 10 hours of TV per week
• average daily calorie intake for women = 1306 cal
• average daily calorie intake for men = 1685 cal

While the causes and contributors to excess weight, and the challenges in maintaining weight loss are different from person to person, it would be worthwhile to consider these permanent habits to improve the likelihood of long term weight management success!

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www.drsue.ca © 2015 

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Keeping Kids Active This Father's Day - And All Year!

In the fight against childhood obesity, it's important to promote an active lifestyle for kids.  Studies show that family based interventions work best to prevent and treat childhood obesity.  Recently, I participated in a fantastic family-oriented triathlon weekend, where kids raced one day and adults the next.  What a great way to get kids interested and enthusiastic in not one but three sports - and adults got to be great role models at the same time!

So this Father's Day weekend, grab your kids and embrace a fun, family-oriented activity - and keep the theme going all year long!

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What Determines Our Daily Energy Burn?

Whether we gain, lose, or maintain weight depends on the balance between calories in, which is what we eat and drink, and calories out, which is the energy that we burn.

So, what exactly determines the calories out side of the equation? 

Our daily calorie burn, also called energy expenditure, is divided into several components: 

1.  Resting Metabolic Rate (RMR)

The RMR is the energy that we use while at, well, rest!  This includes the energy it takes to run our daily functions like breathing, heart pumping, and brain function, and all of the functions of maintenance and repair that go on inside all of our cells on a 24/7 basis.  Believe it or not, this comprises 50-80% of our total daily calorie usage.

The RMR varies greatly from one person to the next, due to differences in lean body mass, age, gender, and genetics.  The RMR is also determined by thyroid hormone levels and the baseline activity of each person's sympathetic nervous system, which produces a baseline level of adrenaline and a tendency towards usage of body fat as an energy source (called lipid oxidation).

2.  Spontaneous Activity

Spontaneous activity refers to everything that we do to move around in a day, from daily living activities to purposeful exercise.  Although one might think this is the biggest part of our daily calorie usage,  it accounts for only 10-25% of our total calorie burn in most people.  

The calorie burn from spontaneous activity varies a lot from person to person, with the biggest variance between individuals actually being due to all of the spontaneous activity excluding purposeful exercise, hence the name non exercise activity thermogenesis or NEAT.  NEAT includes everything from the calories burned during work activities, transport from place to place (eg walking vs driving), and even the amount we fidget!  Interestingly, our tendency for fidgeting behaviors seems to be largely genetically determined.  So, a person who is less inclined to be 'fidgety' will burn less calories in NEAT than a person who is more inclined to be fidgety.    People who have a higher sympathetic nervous system drive tend to have higher NEAT as well. 

The calorie burn from spontaneous activity also depends on body weight, as it requires more calories to carry a higher body weight through life's daily activities.  

3.  Thermic Effect of Food

The thermic effect of food refers to the calories it requires to actually digest the food that we eat, and comprised about 10% of our daily calorie burn.  This can vary somewhat, depending on the types of food eaten (protein requires more calories to digest than carbs or fat), and by sympathetic nervous system activity.  However, the jury is still out as to whether differences in the thermic effect of food plays a role in obesity or not.  

So, a few tips to take away in terms of weight management: 

• With weight loss, the daily calorie burn in resting metabolism and spontaneous activity actually decreases, because there is less weight to maintain and carry around in a day. (Think of a 20 lb weight loss like taking off a 20lb backpack - less weight to carry around means lower calorie burn).  Our metabolism actually slows when we lose weight as well, further decreasing the calories that we need to eat.  So, the 'calories in' side of the equation needs to be scaled back as a person is losing weight, to stay in tune with the decreased calories burned with weight loss. 
• Think about being NEAT!  In other words, try to put more movement in your day.  Rather than being still after dinner, go for a walk instead.  Take the stairs instead of the elevator.  Look for a further parking spot instead of a closer one. 
• Use an exercise program to burn calories, but also to gain muscle mass (as a higher muscle mass increases your RMR). 

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ENDO 2015: Performance Enhancing Drugs

Late yesterday at the Endocrine Society's ENDO 2015 conference, I attended a fascinating session about performance enhancing drugs given by Dr Shalender Bhasin.  

When we think about performance enhancing drugs (PEDs), we tend to associate their use with elite athletes who are using them to get an edge to win a game or a race (with the cycling scandals being an example).  While this certainly does occur, the far more common abuse of PEDs is actually amongst recreational weight lifters, who use PEDs to improve their aesthetic appearance (ie to looked as cut and ripped as possible).  Those that use PEDs for muscle appearance may be at an even higher risk of adverse health effects than the elite athlete, because recreational body builders are more inclined to use these drugs for many years continuously, whereas elite competitive athletes tend to use them more intermittently, usually limited to a few years, and usually supervised by sports med physicians.  (That being said, let's be clear: any use of PEDs can be very dangerous, 'monitored' or not.)

The use of PEDs by men with the goal of enhancing their aesthetic appearance sheds light on an important issue that doesn't get enough attention: namely, that it is not only women, but also men, that are at risk of body image disorders in our current society.  While women may feel a social pressure to emulate the wafer thinness of some celebrities or models, men may also feel pressure to emulate their Hollywood counterparts, to be more chiseled and buff than may be obtainable under normal physiologic circumstances.  A term called Muscular Dysmorphic Syndrome has been coined to describe the condition where an individual (usually a man) is preoccupied with muscularity and leanness, causing dissatisfaction with the person's own body size and shape to the point where it results in impaired function in occupation and social life. 

Muscular Dysmorphic Syndrome with resultant abuse of performance enhancing drugs (PEDs) can be difficult to detect.  This group of individuals typically do not come to doctors for help, and if they do, may not admit that they are using PEDs.  This is a grave concern, because there are multiple (including some life threatening) risks of PED use, with the particular list of risks depending upon the drug or drugs being used.  (PEDs can vary from testosterone derivatives, to growth factors, to hormone modulators, to diuretics, to Beta-2 agonists, to peptides, to stimulants - or any combination of the above).  

As Dr Bhasin eloquently pointed out, the best diagnostic tool that we as health care professionals have to diagnose both Muscular Dysmorphic Syndrome and resultant PED abuse is a good conversation - ie, to proactively ask our patient about it if suspected; and, the ability to have an empathetic, compassionate discussion with our patient about it.

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www.drsue.ca © 2015

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