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Is Aerobic Training Best for Fat/Weight Loss?

That’s What a New Study Concluded

Duke University researchers concluded that aerobic exercise is optimal for reducing fat and weight. They also found that aerobic exercise alone bested a combination of aerobics and weights. Hmmm, sounds a bit myopic. I don’t question the findings, but I do wonder about the conclusion. Is steady state aerobic exercise best for losing fat/weight and keeping it off? Is adding weight training a waste of precious time?

Let’s go inside the study (first published September 27, 2012, in the Journal of Applied Physiology) and look at the details. 

To evaluate the inclusion of resistance training in recent guidelines on exercise for weight loss and maintenance, exercise physiologist Leslie H. Willis, MS, and colleagues compared sustained aerobic training, resistance training, and a combination of the two. Their bottom line objective was to determine the optimal mode of exercise for losing weight and keeping it off.

Beginning with 234 middle-aged (47-52) overweight or obese men and women, the researchers randomly assigned participants to one of three 8-month exercise protocols: 1) Resistant training (RT); 2) Aerobic training (AT); and 3) A combination of the two (AT/RT). They measured changes in body weight, fat percentage, fat mass, lean body mass, and waist circumference. (Only 119 finished the intervention.)

The RT group lifted three days a week (3 sets, 8-12 repetitions) or about 180 minutes/week. The AT group did about 12 miles of jogging per week (65-80% of peak VO2) or about 133 minutes/week. The combination group did both. (There was a four month run-in phase before the intervention and testing began.)

Here’s what they found: 

The RT and combination groups increased lean body mass (2.4 lbs and 1.8 lbs), while the AT group showed a slight decline in lean body mass (0.2 lbs). The RT group gained weight (1.8 lbs), while the AT and combination groups lost about the same amount of weight (~4 lbs). The combination group lost more fat mass (5.4 lbs)—and reduced fat percentage more—than the AT group (3.7 lbs). The combination group also recorded the greatest reduction in waist size, followed by the AT group. Fat mass and waist circumference were essentially unchanged in the RT group.

Which group came out ahead? What do you think?

For the researchers, the decisive factors were reduction in total body mass (weight and fat)—and time commitment. As noted, RT alone did not reduce weight or fat mass; AT alone was significantly better than RT alone for reducing fat mass and weight. As the researchers saw it, combining the two modes of training did not add sufficiently to the result to justify the time commitment involved.

“While requiring double the time commitment, a program of combined AT and RT did not result in significantly more fat mass or body mass reductions over AT alone,” Willis et al wrote. Again, the weight loss was essentially the same, while the combination group lost roughly half again more fat mass than AT alone. 

They concluded: “Balancing time commitments against health benefits, it appears that AT is the optimal mode of exercise for reducing fat mass and body mass.”

Surprised? Disappointed in the researcher’s conclusion? I was. Let’s talk about it. I see the results differently.

*  *  *

The combination group was the winner, with half again more reduction in fat percentage, substantially more shrinkage in waist circumference, and second only to RT alone in lean body mass gain. Losing the same amount of weight with those added benefits is clearly a better outcome. Furthermore, the time commitment for the AT/RT group could very likely have been cut in half with the same or better results. For an example where that was the case, see the recent study from McMaster University in Canada:  http://www.cbass.com/Weights_Aerobics.htm

No wonder half the participants dropped out before the intervention was concluded. My guess is that not many untrained heavy people would want to spend three hours a week lifting weights or a like period of time jogging 12 miles a week, much less do both. They might do it with researchers looking over their shoulder, but on their own? I doubt it. Thirty minutes of lifting combined with twenty minutes of interval training would’ve been more efficient, more interesting—and probably more productive.

Sub-max interval training would be a good option; see http://www.cbass.com/SubMaxIntervals.htm . A big advantage of interval training is the involvement of the fast-twitch muscle fibers. On the other hand, jogging and other forms of steady state aerobic exercise call into play primarily the slow, endurance fibers, leaving the fast fibers—roughly half the body—to shrink and eventually disappear. Fast twitch muscle loss is a major reason why most people get weaker—and fatter—as they age.

As was shown in the Willis study, resistance training builds lean muscle mass—while AT can contribute to muscle atrophy. Resistance training, like AT, can be made more efficient and more appealing.  

Rather than the hour-long RT workouts in the Willis study, it would have been more efficient and practical to do multi-joint exercises. For example: Squat or Leg Press, Bent-over Row, Pulldown, Bench Press, and Shoulder Press. One or two sets of those five exercises cover the major muscles of the body and can be done in about 30 minutes.

High intensity exercise (aerobic or resistance) has benefits not seen in sustained aerobic exercise. For example, interleukin-6 (IL-6), the most powerful metabolic signaling agent released from muscle, is sent out as soon as muscle starts to contract and move. It is released in greater amounts as the activity becomes more intense. IL-6’s actions help dampen inflammation, raise testosterone and growth hormone, increase fat burn, regulate glucose, reduce weight, increase muscle mass, and fine-tune fuel metabolism. In addition, interleukin-15 (IL-15), released primarily through weight training, encourages muscle sparing and fat burning. It is a major factor in determining the body’s muscle-to-fat ratio. Jogging, on the other hand, doesn’t trigger the release of adequate amounts of IL-6 or IL-15, because it doesn’t include the short bursts of intense energy expenditure needed to produce it in sufficient amounts. See http://www.cbass.com/MuscleTalk.htm for more details.  

Two interval sessions and two short weight workouts each week or one of each and a combo workout would produce results equal to or better than those seen in the Willis study. Plus, that routine would be more interesting and more likely to be continued after the intervention is over.

Then again, sustained AT alone may be just the thing for people whose only concern is losing weight and body mass. Many people, perhaps the majority, are in that category. All that’s needed is a pair of running flats and a bathroom scale. The choice is yours.

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