Weights or cardio for fat loss? Metabolic responses to training
A well balanced fat loss programme should incorporate both resistance and cardiovascular training as both have their benefits with health and metabolic reactions that cannot be ignored. However, what type of training is the most effective?
Firstly we need to look at metabolism; when designing a diet or fitness programme we take into account the Resting Metabolic Rate in determining the amount of energy required to maintain the bodily functions at rest and during movement. In conjunction, we monitor The Thermic Effect of Feeding in relation to the Thermic Effect of Activity.
So, fundamentally, if you want to lose weight you have to create a negative energy balance in your body by expending more calories than you consume. However, there is a difference between losing weight and losing fat. Weighing the body is futile for fat loss, as muscle is denser than fat, when fat is lost and muscle is gained you would be smaller but potentially weigh the same. This leads people to become confused and fear that their exercise regimes are flawed.
If fat burning is the goal then striving to enhance the body's fat burning ability is paramount. This desire to burn calories leads people to perform hours of steady state (‘continuous’) cardio, counting calories as they go. However, is this the optimal way to train or could we use our time more effectively?
True, the longer the cardio sessions, the more calories potentially burnt, depending on weight, intensity, time, type and other factors. Of course this will help to reach the overall goal but here's the problem; overtraining or too much cardiovascular exercise will cause the body to use muscle for fuel and hold on to the visceral body fat instead of burning it, ultimately forcing the body into a catabolic state. Over the long term, the wrong type and timing of cardio can lead to the loss of lean muscle mass, which then causes a reduction in the amount of calories burned by the body at rest, ultimately to the detriment of metabolism (Westcott, 2009).
Characteristically, resistance training is anabolic in nature and causes a breakdown in muscle tissue, leading the body to adapt by building muscle (hypertrophy). When you burn calories doing endurance style aerobic training, your body adapts by slowing your metabolism down, up-regulating the enzymes that store body fat and catabolising muscle.
Therefore, for those looking to build a lean, healthy looking physique where fat loss is the goal, resistance training should be favoured as the overall calorie burning benefits you receive from it typically outweigh that of steady state cardio. Whilst it may not burn as many calories as aerobic training per minute during the workout, the after-burn effect it elicits is advantageous. Gilette et al (1994), concluded that high resistance training, tested at 5 sets, 10 exercises, 8-12 reps at 70% 1RM, induced a larger Excess Post-exercise Oxygen Consumption (EPOC) reaction in comparison to aerobic exercise tested on subjects at 50% VO2 max for 60 minutes.
A reaction to the basal metabolism is a welcome effect and result of holding more muscle. As the muscles are broken down during the workout, they use energy in an attempt to replenish and re-construct. Therefore, the more muscle carried the higher the resting energy expenditure, which equates to more calories (mainly from fat) being burned post workout. This is due to the fact that resistance training will accelerate the turnover of protein to repair muscle, which is in itself metabolically challenging. This is especially true with eccentric loading and higher intensity exercise which induces a higher reaction to BMR, EPOC and ultimately lean muscle mass (Prawee 2006). By maintaining intensity, the resynthesis of muscle glycogen is fuelled by free-fatty acids so they are used for energy purposes rather than diverted into storage.
In comparison, the EPOC reaction to lower intensity aerobic training is inferior. LaForgia, Withers and Gore (2006) researched exercise intensities and concluded that higher EPOC values were greater with higher intensity training in comparison to continuous aerobic training.
Therefore, why is cardiovascular training so misinterpreted and misused in the fat loss battle?
Steady state cardio is often favoured due to perceptions of the fat burning zone and the concept that the body burns a greater amount of fat at lower compared to higher intensities when performed at less than 70 percent of maximal capacity for 20 minutes or more. Whilst it has been researched and proven that the body does indeed burn a greater percentage of fat at lower intensities, more total calories are burned during higher intensity activity which equals a greater overall calorie expenditure from fat.
In addition a resistance programme will support a better hormonal environment by lowering adipokines, (the chemical that creates more fat and breaks down muscle), elevating metabolism and achieving a negative energy balance more efficiently.
This muscle gain challenge then becomes a long term strategy for fat loss if the acquired muscle is maintained. So, when we compare this to the catabolic effects of long bouts of steady state cardio we can start to understand the cortisol gremlins that arise from this, breaking down muscle tissue and inhibiting fat loss. As a source of fuel muscle tissue is converted to glucose, leading to increased fat accumulation especially around the midsection, ultimately setting us back from our fat loss mission.
A rise in cortisol levels is also apparent in resistance training, however the simultaneous increase in testosterone and growth hormone offset this, supporting lean muscle gain instead.
In conclusion, metabolic manipulation is key in avoiding fat loss mistakes and ensuring that the body uses energy to repair from intense training sessions. Resistance training will create a more efficient steady state of metabolic enhancement and effectively sculpt a furnace for the improvement of lean body composition. Surely then cardiovascular and resistance training can be adapted to complement each other when done using certain principles?
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