Resistance training or cardio for fat loss? Why not both?
The cause of obesity is a complex combination of environment, behavioral habits and genetics (Paddon-Jones). In the United States, 69% of adults are overweight and 36% are obese (Sword). Obesity is associated with health conditions including hypertension, type two diabetes, coronary heart disease, stroke, hyperlipidemia, respiratory problems and several different types of cancer (Hammond, Sword, Barnes). Risk of hypertension is 40-60% greater in overweight individuals and two times greater in obese individuals compared to non obese individuals. The risk of coronary heart disease is also greater in obese individuals compared to non obese individuals (Hammond).
The estimated medical cost of obesity is $147 billion dollars a year (in 2008). Childhood obesity accounts for approximately 14.3 billion dollars annually as well. Indirect cost need to be taken into account too. For example, being absent from work and decreased productivity at work because of obesity cost money. Although it is difficult to get an accurate number, the estimated total cost of obesity per year is over $215 billion dollars (Hammond).
Obesity is the result of long term positive energy balance (McQueen) caused by excessive calorie intake and lack of regular physical activity (Paddon-Jones). Excess calorie intake is what makes people obese despite many misconceptions that certain foods make people obese. Therefore an intervention based on decreasing calorie intake through dietary modification and increasing calorie output through exercise should be implemented (other personal characteristics of the client make the implementation of this more difficult than it sounds, saying eat less exercise more without a strategy rarely if ever works)
Resistance training can help increase lean body mass and also prevent the loss of lean body mass while in a caloric deficit which is necessary to lose weight. It is desirable to maximize fat loss while minimizing muscle loss when on a weight loss program.
Resistance training by itself probably is not effective for the desired amount of fat loss most clients are seeking. However, the trainer should look at the chronic adaptations and benefits that occur from resistance training. Muscle is more metabolically active than fat, 13kcal/day compared to 4.5 kcal/day (Wang). This may seem like a small difference but if a client puts on 15 pounds of muscle that’s almost 130 extra calories burned per day.
When a client progressively increases the weight they lift they burn more calories. This may seem obvious but as a client or athlete gets stronger they will burn more calories with a similar rep and set scheme. For example, squatting 4 sets of 10 with 200 pounds would burn fewer calories than 4 sets of 10 with 300 pounds. The time spent exercising would be the same but more calories would be burned. Furthermore, with increases in strength are usually accompanied by increases in muscle mass meaning the client or athlete would be burning more calories at rest as well.
Furthermore, resistance training could also help with cardiovascular function. In one study, (Escamilla) the authors stated that deadlifting for 4 sets of 8 at 175 kg would have the lifter expending 3.5 L *O2/min -1 which is relatively high compared with walking, jogging, and other common actives (Escamilla).
A 2007 article (Robergs) wanted to examine the energy expenditure of the bench press and the back squat. They used steady state squatting with light weight to predict the actual cost of resistance training at higher intensities.
Let’s say you are working with a strong client who does 3 sets of 10 at 275 pounds, we’ll also say the client weighs 190 pounds and the distance the bar travels is 45 centimeters. Below is the equation that Robergs used:
Y= -1.424 + (.022) (X1)+ (.035)(X2)
X1= load in kg = 275 pounds on the bar + 190 pounds body weight / 2.2 = 211 kg
X2= distance in cm = 45 cm
Distance was defined as the span between where the load started and where it completed the eccentric portion of the contraction.
Y= -1.424 + (.022)(211kg) + (.035)(45cm)
VO2 = 4.793 (L * min -1)
It is generally recommended on the squat to perform a controlled 2-3 second eccentric with an explosive concentric. We’ll say each rep took 3.75 seconds (this is roughly based off the time it took for each rep in the study by Escamilla, so it is open for critique).
30 reps would equate to 112.5 seconds of squatting or 1.875 minutes of work.
If the VO2 is 4.793 L *min-1 then the client was burning around 24 calories per minute (5 calories/ L of O2 consumed) or roughly 45 calories throughout the whole squat session. Now let’s also include rest in between sets where VO2 is still elevated, let’s say 60 seconds. This would equate to two minutes of rest and then a total of almost 4 minutes which is around 90 calories burned.
Robergs et al. did find that their equations predicted values that were higher than previously predicted. Perhaps because other studies didn’t take into account all energy systems. Regardless it would seem that resistance training is a great way to burn calories while maintaining lean body mass. Oxygen consumed is comparable to jogging as well. If a person’s goal is to lose weight and keep muscle they may want to try resistance training with mulitjoint movements such as the squat or deadlift.
Despite this calorie expenditure, because it may be only applicable for more advanced lifters (someone doing half the weight would burn half the calories), resistance training probably doesn’t have a large direct impact on weight loss especially for beginners. However, it may have a bigger indirect impact. The chart below is from Donnelly et al.
Resistance training also leads to greater fat oxidation and increased physical activity outside of the gym which can also lead to decreased body fat (Donnelly). Because weight loss is all about expending more energy than you take in, a combined approach of cardiovascular and resistance training may be the most appropriate method.
A combination of aerobic and resistance training may be the best choice for weight loss. Aerobic training activates lypolysis, the breakdown of lips, and resistance training helps to preserve lean body mass (Park).
Part et al. conducted an experiment to observe the effects of aerobic training compared to a combined resistance training and aerobics program on thirty middle aged obese women, aged 40-45. Weight and body fat dropped in both groups whereas it rose in the control group. Lean body mass only increased in the combined training group. Because of this the combination of aerobic and resistance training is favorable for better body composition. In the aerobics group the subjects decreased body weight by 4.7 kg and dropped 9.2% of their body fat. In the combined group subjects dropped 6.4 kg and 10.3% body fat. The intervention was 24 weeks long (Park).
Cardiovascular training may initially help to burn more calories and it may be appropriate for obese individuals who need to do low impact exercises such as walking or water aerobics. However, for favorable long term improvements in body composition resistance training is the best option. Resistance training helps to increase lean body mass which increases daily caloric expenditure. Lifting weights, especially for reps may be comparable to cardiovascular training relative to oxygen consumption as well.
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