Tyler Robbins Fitness

B.Sc. Biochemistry, Certified Strength and Conditioning Specialist (CSCS), Certified CrossFit Trainer (CCFT/CF-L3), USA Weightlifting Level 1

Filtering by Tag: HIIT

Does exercise actually burn fat?

How absurd is this?

How absurd is this?

So, does exercise really actually burn or melt body fat? Well, a very plain and simple answer would be no, not really. The answer is certainly more complicated than that, and I plan on explaining myself further, but this is certainly a topic that most people get wrong, or are greatly misinformed.

Sure, a lot of you may read this blog and think, "Your argument is just semantics. Exercise (in a roundabout way) burns fat!" Well, maybe. Maybe this could be considered semantics, but I personally believe this plays a crucial role in how people perceive not only the role of exercise, but the role of food and their diet as well!

Heavy science jargon and content ahead. I have done my absolute best to explain what is going on here. You've been warned. If you're still here, let's dive in.

I came across this interesting review the other day:

Abdominal fat reducing outcome of exercise training: fat burning or hydrocarbon source redistribution?

Abstract

Fat burning, defined by fatty acid oxidation into carbon dioxide, is the most described hypothesis to explain the actual abdominal fat reducing outcome of exercise training. This hypothesis is strengthened by evidence of increased whole-body lipolysis during exercise. As a result, aerobic training is widely recommended for obesity management. This intuition raises several paradoxes: first, both aerobic and resistance exercise training do not actually elevate 24 h fat oxidation, according to data from chamber-based indirect calorimetry. Second, anaerobic high-intensity intermittent training produces greater abdominal fat reduction than continuous aerobic training at similar amounts of energy expenditure. Third, significant body fat reduction in athletes occurs when oxygen supply decreases to inhibit fat burning during altitude-induced hypoxia exposure at the same training volume. Lack of oxygen increases post-meal blood distribution to human skeletal muscle, suggesting that shifting the postprandial hydrocarbons towards skeletal muscle away from adipose tissue might be more important than fat burning in decreasing abdominal fat. Creating a negative energy balance in fat cells due to competition of skeletal muscle for circulating hydrocarbon sources may be a better model to explain the abdominal fat reducing outcome of exercise than the fat-burning model.

Lots of science talk, let's break things down and give some thoughts as to what is being discussed here.

Fat burning, defined by fatty acid oxidation into carbon dioxide, is the most described hypothesis to explain the actual abdominal fat reducing outcome of exercise training.

This is one of these popular "facts" making its way around the internet lately. The idea that as you exercise and burn fat, the fat then just starts melting and you magically breathe it out as carbon dioxide. Sure, carbon dioxide is a by product of metabolism and respiration, and you certainly burn some fat during exercise, but it isn't really that simple.

This hypothesis is strengthened by evidence of increased whole-body lipolysis during exercise. As a result, aerobic training is widely recommended for obesity management.

Right. This has been heard for years. This is actually one point that seems to be at least somewhat well-known to be a mistruth now. That just because adipose tissue (body fat) is only burned in the presence of oxygen (oxidation), then low-level exercise must be best for burning fat. Right? Go for a nice long, easy run on the treadmill and you will get thin and sexy. Well, not exactly. My readers should know that intense exercise is better suited for reducing body fat by now so lets move on.

anaerobic high-intensity intermittent training produces greater abdominal fat reduction than continuous aerobic training at similar amounts of energy expenditure.

Study after study after study has shown just this - high intensity interval training is more effective for reducing body fat than steady state cardiovascular exercise.

significant body fat reduction in athletes occurs when oxygen supply decreases to inhibit fat burning during altitude-induced hypoxia exposure at the same training volume

Ah good, now things get interesting. So what this states is that body fat is reduced more in individuals that have decreased oxygen supply. Doesn't oxygen need to be present to burn body fat? Well, as the previous statement pointed out to us, high intensity exercise - you know, the type that has you gasping for air (oxygen deprived), is actually best at obtaining or maintaining an optimal body fat percentage.

Lack of oxygen increases post-meal blood distribution to human skeletal muscle, suggesting that shifting the postprandial hydrocarbons towards skeletal muscle away from adipose tissue might be more important than fat burning in decreasing abdominal fat.

This gets into the meat of this paper's argument, and one that I will elaborate on below. People need to stop thinking of exercise as a fat burner, and instead consider exercise (both resistance training and "cardio") as a means to make your body a better fat-burning machine.

Creating a negative energy balance in fat cells due to competition of skeletal muscle for circulating hydrocarbon sources may be a better model to explain the abdominal fat reducing outcome of exercise than the fat-burning model.

Once I dove deeper into this paper, I got a better sense of what point the authors were trying to prove. Your muscle cells and fat cells both have the ability and goal in mind to store energy. In fact, there seems to be a competition between the two. Your body is constantly varying its sources of energy based on your level of activity. When you are exercising intensely, your body is primarily using glucose as a fuel source, for example. Sure, there is some fat being oxidized, but the primary fuel source is glucose.

Compare that to the amount of fat being burned between aerobic exercise, resistance exercise, and non-exercise. Sorry resistance trainee camp, not even you can argue that resistance training is "better" than aerobic exercise for burning fat - at least not directly.

This one is telling for the "exercise until you puke" camp. The notion that the harder you exercise, the more fat you burn is total b.s. as well. Do I think intense exercise is important? Absolutely. Do I think intense exercise is necessary for weight loss and body fat reduction? Not really, or at least not primarily. Some is good, but only to a certain level.

So what is the point to all of this? Well this is where the semantics comes in.

The current understanding is that when you are exercising, your body is literally burning away those love handles as you crank through all those burpees or squats. As we saw in figure A above, this is simply not the case. Yes, intense exercise promotes lower body fat percentages, but not because the fat is literally being burned and exhaled as carbon dioxide. Ok, then it must be the post-workout "burn" where metabolism is revved up. That is a common theme, correct? Again, not the case. Because oxygen must be present in order to burn fatty acids as a fuel source, by exercising intensely, you are specifically forcing your body to turn to glucose as a primary energy source.

So low-level exercise is better for burning fat, right?

Well, no. Research has proven time and time again that shorter, intense exercise is not only more efficient and effective than low-level, steady-state exercise to improve cardiovascular health and a healthy body-fat percentage.

So what gives?

As this review points out, the mindset as to what exercise actually does to your body and how body fat is reduced is the most important part. Exercise, and more specifically, intense exercise (ideally with external resistance, i.e. weights) not only builds strong muscles, but it turns your muscles into energy consuming machines. This causes a domino effect.

  1. Body fat (adipose tissue) and lean tissue (muscle) are constantly competing over consuming incoming calories. The body seems to give preferential treatment to muscles the harder they work.
     
  2. Energy that is not consumed and stored in muscles goes to body fat.
     
  3. Carbohydrates are broken down into glucose. When your body is not active, glucose is not being burned as readily by muscles, so there is more glucose present and glucose becomes the primary energy source even during low-level activity (most of the day).
     
  4. Fatty acids from adipose tissue are the primary energy source for majority of your day (i.e. the time you aren't working out intensely). But if glucose is present, blood sugar (glucose) becomes the energy source of choice.
     
  5. If your body is using blood glucose as an energy source, body fat deposits are not reducing.
     
  6. If your muscles are consuming large amounts of energy, especially carbohydrates, then your body primarily uses fatty acids (adipose tissue) as the energy source.

Conclusions

So although this isn't necessarily different than what most people should already know - intense exercise makes you thin and keeps you healthy, the mindset for how this works should change. Resistance training is used to not only strengthen the connective tissues of the body, but to make your muscles greater calorie-burning machines.

Carbohydrates should be consumed almost entirely just prior to, and/or immediately following a workout in order to reduce the amount that is stored as body fat.

Although intense activity is great and very important for overall health, the more active you are the rest of the day during "low-level activity" (walking, working, playing, etc.), the more effective your body will be at reducing your body fat percentage.





Why are shorter workouts so effective?

Beachbody has released information about their newest fitness program called Insanity Max :30. This is yet another product in a recent string of fitness programs from Beachbody targeting that 30 minute exercise window. Notable others include: P90X3, Focus T25, 21 Day Fix, etc. So why are workouts becoming shorter and shorter.

Well, as I have discussed in the past, I believe shorter workouts are more appealing to people  wishing to start their fitness journeys. Let's face it, it is much more attractive for folks to think of starting a new workout program that is just 25-30 minutes a day as compared to either 45-60 minute home workout programs or even longer trips to your traditional gym.

Oh, trust me, I know. The video seems quite cheesy. Some people like that kind of "flare." It feels like I am watching a trailer for a Hollywood movie. Let's not forget that this is a fitness product, and products have to be appealing to sell more. As cheesy as this trailer can seem, I will not deny the fact that I am extremely excited about this program and will be purchasing it on day 1 for my wife and I.

I have been through Shaun T's original Insanity program. I have also done Insanity: The Asylum, his more sports-themed, punch-you-in-the-face workout program. I have to admit, however, that I much prefer lifting weights and working on increasing my muscle size and strength, so doing 45+ minute mostly-cardio-based routines is not that appealing to me.

Having said that, cardiovascular exercise is important for brain and cardiovascular health. Sure, it burns calories (more, the more intensity you bring), but the main focus, in my opinion, about doing cardiovascular exercise is to improve your heart and lungs and overall health.

I have tried Focus T25, and it is ok. The workouts are challenging and some are actually quite fun to do, but it just isn't the same as Insanity (let's be honest). So, when I heard about Insanity, but in short 30 minute workouts, my interest in home-based cardio routines suddenly piqued again.

So why shorter workouts? Can they still be as effective? You bet they can, here's why?

Take this study, for example:

"While other low volume HIT protocols have reported non-significant (Burgomaster. 2005, 2006) or small (below 10%) increases in aerobic capacity (Burgomaster. 2008; Hazell. 2010) the current protocol induced rela- tively large increases in both VO2peak (+19%) and an- aerobic performance (+12% - 14%). These findings con- firm the results of Tabata et al.(1996) who reported ele- vated VO2peak at both 3 and 6 wks of training, and demonstrate that increases in VO2peak occur following 2 wks of training. Interestingly, while VO2peak is traditionally believed to be determined by cardiac output, a recent report demonstrated increased VO2peak without an accompanying increase in maximal cardiac output following treadmill sprint interval training (MacPherson. 2011)."

So what does this mean? Well, basically, something that I have stressed time and time again. Short bursts of intense exercise is very effective at keeping you "fit" and improving your VO2Max. VO2Max, basically, is how effective your body is at utilizing oxygen. The more efficient and effective your body is at utilizing oxygen, the harder, faster, and more effective your exercise and everyday activities can become. Not only that, but your body then becomes a far more efficient machine at burning body fat stores as a primary energy source, lowering your body fat percentage.

The study had participants using Tabata-style exercise (similar to what will be used in Insanity Max :30), which is a form of HIIT (high intensity interval training). The study subjects completed 4 workouts per week, each consisting of 4 minutes of exercise (8, 20 second intervals, 10 second break between. Total time = 4 minutes). Yes, you read that correctly. In just 16 mins of exercise every week, these individuals improved their VO2Max, but maybe more importantly for many of you, they also had an increase in mitochondrial protein.

If you remember back to your high school biology days, mitochondria are considered the "power plants" of your cells. They have a number of functions, but the function that is most important to those exercising, is the production of energy through aerobic means.

So, with intense exercise, your body becomes more efficient at burning body fat as a primary energy source, leading you to be more effective at everything else you do throughout your day, burning more body fat during every other activity that you are doing.

So, we know that short, intense intervals are great for improving aerobic conditioning. But what about burning calories and dropping body fat?

A study done by McMaster University in Hamilton, Ontario, Canada found that men who performed sprint intervaltraining for a total of 2.5 hours (including recovery) over the course of 2weeks has the same results as the group who performed endurance training for atotal of 10.5 hours over the same time period.

Yes, its alright to go back and read that again. 1/5th of the time for the same results! Another study following a group of 15 women found that high-intensity exercise (40 to 45 minutes approximately four times weekly at a mean HR of 163 bpm) reduced body fat by about 5 percent over the course of 15 weeks versus a virtually unchanged percentage in the group that performed exercise at a lower heart rate (132 beats per minute).

Long-duration cardio sessions have a place in your training block if you are training for something specific like a marathon in which you wish to improve your overall time. However, when it comes to aerobic conditioning, calorie burn, and overall health, about 30 minutes of intense exercise is really all you need!





Strength and Conditioning Tips

I have compiled a helpful list of training tips below that I am sure everyone can learn something from, enjoy!

Training Time

This tip is actually a twofer (broken into 2 parts). Men and women alike are always asking when the best time of the day is to work out, so that is why this is broken into two. For men (generalizing here), they want to know when the best time of day is to work out to grow big, strong muscles. Many people will tell you that working out in the afternoon or evening is the best time for muscle growth for a number of reasons, but simply is not true. The Journal for Strength and Conditioning Research has said that consistency is the key here. If you only have time to hit the weights in the morning, do that! The study showed that men made equal strength gains regardless of what time of day they worked out.

Similarly, women (again, generalizing) want to know when the best time of day is to exercise to burn fat. Again, consistency is the key. There are pros and cons to exercising either morning or night. For example, exercising in the morning can rev your metabolism for the rest of the day, whereas exercising in the evening has the potential to burn more calories as your body's metabolism is potentially at its highest. As I have said before, doingsomething is always better than doing nothing, so if you only have time in the morning to exercise, do that! I personally exercise in the morning because that's what fits my schedule, but if it doesn't suit you, then fine!

Pack on the Protein

I see this one time and time again. People think that in order to grow big, strong muscles, they need to cram as much protein into each meal as possible. Studies have shown that eating 30 grams of protein in a meal yields the same benefits of eating 90 grams does. This is a perfect example of "more isn't necessarily better". Instead, you should aim to have protein in small doses throughout the day. Keep one thing in mind, however. Protein seems to have this aura attached to it now that it is this wonderful "weight-loss" food. Protein still has calories, and ingesting too much protein can still result in unwanted body fat if unused, so make sure your diet is properly proportioned. Not only that, but if all you are doing is eating protein all day, you will likely be missing out on important vitamins and nutrients that can only be found in whole grains, fruits, and vegetables!

Muscle Loss

For the longest time, there was this belief that as people age, their muscle tissue decreases. This is in fact true, but this is a sort of chicken-and-egg problem. Does your muscle tissue disappear because you age, or because you stop using your muscles as you age? Studies are now showing that it is in fact possible to continue muscle growth with strength improvements later in life. Yes, men have lowered testosterone as they age, but there is more to it than that. Once you hit the age of 65, sure, you may not be making major muscle gains, but you can still use resistance training to reduce the loss of muscle. Not only that, men and women can greatly benefit from resistance training throughout life to help strengthen bones, muscles and connective tissues!

Do It For Your Brain

Sure, many people like to exercise to try and look a certain way. Unfortunately, many personal trainers will market these types of things to you as well. I have a swift kick of reality for you though. Unless you have tremendous genetics, or photoshop (or a combination of the two), you are never going to look like some of those models or Hollywood celebrities. Not only that, but chasing "the perfect image" will only end in disappointment and despair. Instead, you should exercise to feel better about yourself in your own skin, not to mention the mental and body benefits that comes along with it. Think of how great you feel after a good workout. Wouldn't that be great to bottle that up and take a swig of that every day for the rest of your life?

Go Fast and then Go Home

I probably sound like a broken record here, but unfortunately some people just don't get it. I see and get asked by people all the time why they are not getting/seeing results from working out an hour or more at a time. I then see them slowing jogging on a treadmill or elliptical. Instead, why not try HIIT (high-intensity interval training) and cut your workout times in half? Chronic cardio should only be used if you are training for...wait for it...a cardio event such as a marathon or triathlon, etc. Instead, most people can get into their gym, exercise using HIIT principles for 20-30mins and then be done with an even better workout than something that takes twice the time.

A study done by McMaster University in Hamilton found that men who performed sprint interval training for a total of 2.5 hours (including recovery) over the course of 2 weeks has the same results as the group who performed endurance training for a total of 10.5 hours over the same time period. Yes, its alright to go back and read that again. 1/5th of the time for the same results! Another study following a group of 15 women found that high-intensity exercise (40 to 45 minutes approximately four times weekly at a mean HR of 163 bpm) reduced body fat by about 5 percent over the course of 15 weeks versus a virtually unchanged percentage in the group that performed exercise at a lower heart rate (132 beats per minute).