Archive | March, 2014

The Burning Question: How Important is Meal Frequency?

31 Mar

meal timing and frequency

Intro

Chances are at some point or another in your life you played the “telephone game” – whether it was in grade school or with a group of friends. You know, the game where you and your classmates or a group of friends pass along a message or phrase via whispering from person to person until that message reaches the last individual, in which that individual reports the message aloud.

The majority of the time, the original message gets skewed by the time it is said aloud.

With cliche terminology and illogical advice thrown around by “fitness gurus” in the fitness industry today, it can be a difficult task to find the truth in nutrition and training principles.

Like the telephone game, messages and advice (both good and bad) can become distorted as more receivers pass the original message down the chain.

Meal Frequency and Timing

Just the other day, I came across an advertisement in a fitness magazine promoting eating every 2-3 hours to keep the metabolism “firing” and to minimize muscle breakdown while promoting fat loss.

Individuals setting out a weight loss journey are told they must eat 6-8 small meals per day to lose fat effectively.

Fitness enthusiasts may become increasingly concerned with missing a meal or not getting a meal in within a certain time in fear of the metabolic rate slowing.

Trainers may encourage clients in contest preparation to tote around a cooler all day – containing multiple, individually-packed plastic food containers of portioned chicken breast and a sweet potato, so the client can stoke the metabolic fire by eating every few hours.

campfire

Meal frequency is certainly not a “more is better” approach and should be specific to the individual’s health and fitness goals, schedule, and food preferences.

Let’s consider the bigger picture and take a deeper look.

The Thermic Effect of Food

The basis of eating more frequently to promote fat loss and improved body composition stems from the concept of diet induced thermogenesis also known as the thermic effect of food (TEF).

The TEF in simplest terms is the energy used in digestion, absorption and distribution of nutrients.

Just as we expend energy via physical activity and at rest, we also expend energy via digestive processes following the ingestion of food. Point blank: every time you eat, the TEF increases.

It should be noted that the TEF constitutes ~10% of a total daily energy expenditure based on the composition of macronutrients in the diet.

With that being said, conventional wisdom would tell us in order to reap the benefits of the TEF we should eat more frequently to stimulate the TEF more often.

However, research suggests the TEF is less pronounced with each smaller meal that we eat. So essentially, the less energy (calories) we take in and the more frequently we eat, the lower the TEF (1). This is illogical for those looking to lose weight via calorie restriction as the magnitude of the TEF is decreased by taking in fewer calories.

Point blank: As calories are reduced, the TEF is decreased – making the basis of “stoking the metabolic fire” appear seemingly invalid.

Contrary to popular belief in the fitness industry, a high meal frequency has no “calorie burning advantage” over a lower meal frequency – provided total calorie intake is controlled for (2, 3).

3,200 calories with a specific macronutrient distribution of 50 percent calories from carbohydrate, 30% calories from protein, and 20% calories from fat spread throughout the day in 6 meals is not any different than 3,200 calories with the same macronutrient distributions spread throughout the day in 4 meals.

Meal Frequency and Metabolism

The body’s metabolism is always firing. Some metabolisms fire at a higher capacity. An efficient metabolic capacity is determined by several factors including age, gender, activity level, and proportion of lean body mass (LBM) to fat mass.

A high meal frequency does not significantly increase the human metabolism. Missing a meal or eating a meal at a later time in the day than one normally would does not negatively affect the metabolic rate – provided calorie intake is accounted for. The body’s metabolism simply does not work that quickly.

A trained individual will not enter the ever-so-scary, overhyped ‘starvation mode’ because he or she goes 3 hours without a meal. Contrary to popular fitness dogma, the body will not aggressively eat away at an individual’s hard earned muscle tissue if a meal is missed or delayed.

The human metabolism does not have an inherent biological clock in which it magically stops working. The metabolism is an ever-changing process of building new substrates and breaking down substrates to make energy available.

metabolicclock

The body’s metabolism is constantly switching the “on and off” switch — between maintaining and building substrate (anabolism) and breaking down (catabolism) substrate for energy – depending on the body’s needs.

Failing to recognize that the body’s metabolic needs are in a constant state of change based on physical and chemical energy needs is taking a snapshot of the energy equation and bypassing the bigger picture:overall calorie intake and calorie expenditure.

Meal Frequency and Appetite

For the purposes of regulating appetite, a higher meal frequency may be most appropriate. Distributing daily calories into several smaller meals can help keep hunger at bay.

Bottom line here: when folks consume fewer calories than they need, weight loss will occur. If a higher meal frequency accompanies a calorie restriction, weight loss will occur.

There is nothing magical about meal frequency.

Folks on a calorie restriction of 2,000 calories distributed in 4 meals vs. folks on a calorie restriction of 2,000 calories distributed in 8 meals will lose weight – completely independent of meal frequency.
Alternatively, for a strength athlete with increased calorie needs – a higher meal frequency may be optimal.

However, if the strength athlete prefers larger meals and has a noticeably increased appetite when meal frequency is haphazard and not “set in stone” – a lower meal frequency fits the bill.

Big picture:

1) Determine your calorie and macronutrient needs based on your training and nutrition goals.
2) Distribute your meals based on your individual preference.

Conclusions and Practicality

We all have a different health and fitness agenda. Individual response, training and nutrition goals, and context are paramount in determining what is optimal. Therefore, meal frequency and meal schedules should be structured upon the accommodation of food preferences, tolerances, flexibility, and becoming in-tune with the body’s natural hunger cues — which will vary person to person.

With that being said, an individual looking to decrease body fat may benefit from eating more frequently – since this may allow the individual to regulate appetite given total calorie intake is kept in check. Alternatively, an individual may benefit from eating less frequently since he or she prefers larger meals. If so, this approach may be most optimal for him or her.

The purpose of this article was to dismantle the dogma that it is an absolute necessity to eat 6 smalls per day to lose fat and debunk the misconception that grazing throughout the day stokes the metabolic fire.

Personal preference overrides subjective opinions and anecdotes passed down in the fitness community. Presumed truths passed along in the fitness industry must be examined contextually based on not only a physiological level, but an individualized level as well.

1. Miles CW, Wong NP, Rumpler WV, Conway J: Effect of circadian variation in energy expenditure, within-subject variation and weight reduction on thermic effect of food. Eur J Clin Nutr 1993, 47:274-284.

2. Taylor MA, Garrow JS. Compared with nibbling, neither gorging nor a morning fast affect short-term energy balance in obese patients in a chamber calorimeter. Int J Obes Relat Metab Disord. 2001 Apr;25(4):519-28.

3. Verboeket-van de Venne WP, Westerterp KR. Influence of the feeding frequency on nutrient utilization in man: consequences for energy metabolism. Eur J Clin Nutr. 1991 Mar;45(3):161-9.

The big picture: high-intensity cardio vs. low-moderate steady state cardio

10 Mar

Intro

Walk into the gym and take a look at the cardio section. Chances are you will see a mix of individuals pedaling along on a recumbent bike at a low intensity, folks walking at a brisk pace on the treadmills, and of course – those folks who move lightning fast on the elliptical with absolutely no incline or resistance set on the machine.

The bottom line is that everyone has a different goal. And cardiovascular activity needs to be individualized. However, as a trainer I have noticed a common theme with time. Most of these individuals who do the same cardiovascular exercise routine almost daily have not progressed in body composition as much as one would think with the amount of cardio they are doing.

Maybe improved body composition isn’t the main goal and general cardiovascular and physical fitness is the goal. However, if improved body composition and improved athletic performance and work capacity is a goal – listen up.

Quite often I get asked, “What is the best type of cardio?” The answer to that is……. IT DEPENDS.  It depends on many factors including — training goals, performance goals, training status, and other individualized variables. Most people that ask me this question often want to know the best type of cardio for fat loss or optimal body composition.  

The conversation often leads to the person making this statement, “I have heard that low-intensity cardio burns more fat, so shouldn’t I only do that?”  To better answer that question, we must first understand some physiological principles of fat loss.

The Benefits & Physiological Concepts of Cardiovascular Activity

The benefits of regular cardiovascular exercise are vast — including improved blood pressure, improved blood lipid values, increased insulin sensitivity, and the promotion of feelings of well-being.  Not only is cardiovascular exercise successful at improving health outcomes, but it is often used to enhance sport performance and body composition.

The law of thermodynamics explains that energy cannot be created or destroyed, it can only change form. The food we consume contains energy, known as calories. The calories we consume through food are composed of chemical energy that our body, through many different types of metabolic processes, will transfer into mechanical energy.

The metabolism of energy nutrients (protein, carbohydrates, and fats) result in the production of adenosine triphosphate (ATP).  ATP, often called the energy currency, is important for a multitude of physiological functions. While ATP production is a major priority for our body, not all energy consumed is directly transferred to mechanical energy.

Some of this extra energy is stored as triacyglycerol (fat) in the adipocytes.  This stored fat serves as reserve fuel for our body during a period of fasting or starvation.  You can think of this as our body’s savings account. Much like you keep a savings account for unexpected expenses, your body stores fat so that it can survive if starved.

In times of desperate need of fuel, our body will release stored triacyglycerols to be metabolized for ATP production.  Keep this concept in mind throughout the rest of this article as we discuss the role of cardio exercise on fat loss.

The Issue of Supply and Demand

While reading this article, chances are that you are sitting down.  Even though you are sedentary at the moment, your body is releasing stored fat from your adipocytes into the blood stream.  This fat will be taken to a variety of tissues to be metabolized and converted to ATP.  So actually, at rest you are technically burning fat.  So, if this is true, why is exercise so important?

An increase in physical activity places a greater demand for ATP production.  As certain muscles become active, they need ATP for repetitive contraction.  The exercise intensity will dictate the demand of ATP production.  This is very important to understand.  

As we move from sedentary to highly intense exercise, our body must be able to metabolize substrates (fuel sources) to convert into ATP to be able to maintain the given exercise output.

One thing that needs to be noted is the type of substrate that is metabolized to create ATP.  This chart below shows that the intensity of work will determine the percentage of certain substrates that are used by our body.

 graph (1)

Respiratory exchange ratio (RER) is a ratio of carbon dioxide produced to oxygen consumed.  During steady state conditions, RER is used to commonly used as a means of determining the contribution of fat and carbohydrate to energy expenditure.

At rest, an average individual with a balanced diet has an RER of ~0.80.  The chart above shows that 68% of our energy would come from fat and 32% would come from carbohydrate.  

As an individual engages in physical activity, RER will increase, and the intensity of the activity will determine the amount of increase. 

When exercising near maximal capacity, RER is ~1.00 which means that our body is using carbohydrateas the fuel source.  If this is the case, then this chart is showing that lower intensity activities utilize a greater percentage of fat as fuel.  

This is the reason many “fitness experts” tell people to perform low-intensity steady state cardio for fat loss, and from the information presented above this seems logical.

The Overarching Determinant: Energy Balance and Expenditure

What if I told you the percentage of fat that is burned during exercise isn’t really the most important aspect of cardio for fat loss?  Yes, that is exactly what I am saying.  It doesn’t matter how much fat you burn during exercise. But what does matter is how much fat you burn throughout the day.

In other words, the most important aspect is daily energy expenditure, and in this case maximizing calories burned from exercise. 

The goal for your cardio should be to burn as many calories as possible in the time that you spend exercising.  Remember, the intensity of the exercise will determine the amount of energy expended.  

The following scenario will demonstrate how low-intensity cardio is not as optimal as most people think.

A 200lb male wants to lose weight.  He has two options of cardio to promote fat loss.

1)    30 minutes of walking on a treadmill at 3.5 mph with 3% grade

vs.

2)     20 total minutes of high-intensity interval training (HIIT):

5 minute warm-up and cool down using a treadmill set at 3.5 mph and 0% grade.

Ten 20-second sprints at 10 mph and 0% grade followed by 40 seconds of walking at 3.5 mph at 0% grade.

Which is more effective?

Option 2.  Don’t believe me?  Let’s take a look why.

1)      Walking on a treadmill would elicit ~245 calories burned in 30 minutes.

2)      Performing the HIIT, the same individual would burn ~160 Kcals in 20 minutes. 

EPOC: The “afterburn effect”

But wait, walking on a treadmill at a steady state burns more calories than HIIT. Yes, at face value. Your treadmill will likely read 245 calories burned at the conclusion of your cardio session, but there is a forest beyond the trees here.

One thing that I haven’t yet mentioned, and most people don’t know about is excess post-exercise oxygen consumption (EPOC). 

EPOC refers to the time after exercise where the body is trying to get back to its resting physiological state.  Think of after you get done walking or running.  You don’t immediately go back to normal respiratory function. Depending on the intensity of the exercise, your body is still trying to recover.  Again, intensity plays a significant role in determining the degree of EPOC.

0

Mike doing work on the weighted push sled. High intensity cardio at its finest.

Let’s take a look at this graph.

graph2

The yellow on the picture above is the EPOC.  Notice that the high intensity cardio has a significantly higher EPOC than the low intensity cardio. 

This because it takes a much longer period of time to return all physiological systems back to baseline after working near maximal capacity.During this recovery period, you still have an elevated heart rate, ventilation, and metabolism. 

This elevated metabolism can last for hours, which plays a significant role in weight loss.  Because our metabolism stays elevated, we are now burning more calories at rest throughout the remainder of the day.  At the end of the day, a greater amount stored body fat will have been released and catabolized for energy production.  

As you can see, the amount of fat you burn during exercise is not as important as total calories burned throughout the day.  Fat loss will occur regardless if you shift your focus to expending as many calories in the amount of time that you have available.  

Remember, focusing on the substrate oxidized, whether it is primarily from fat or carbohydrate, during the cardio session is not as important as the total calorie expenditure. Big picture, folks — always keep it in mind!