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Resistance Training Versus Aerobic Training for Fat Loss: A Debate

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It is well established in evidence-based guidance for treating obesity that exercise/physical activity prescription includes aerobic activity, resistance training, and increased non-exercise physical activity.

The most recommended version is aerobic training, progressively increased in volume and intensity for a goal of at least 150 minutes per week of moderate-intensity exercise, like brisk walking, plus resistance training of major muscle groups two to three days, or more, per week. 

The question for this debate is which exercise is more important for fat loss and weight maintenance? Dr. Spencer Nadolsky, a family practice clinician who specializes in obesity and lipidology with an extensive background in athletics and exercise physiology, argued in favor of resistance training against world-renowned exercise scientist John Jakicic, who defended aerobic training for this fun debate. The format allowed each participant 15 initial minutes to establish their arguments, followed by a few minutes of rebuttal and specific questions developed by the moderator to which neither knew the other’s prepared answers. 

Dr. Nadolsky drew the straw to go first and worked the audience with some initial humor by telling a story from when he was fresh out of residency, excited to be at his first Obesity Week, and shared a cab with John Jakicic before realizing who he was. He later found out during the ABOM review course, when John spoke, and others cited Mr. Jakicic’s work. Fast forward to the invitation to this debate, and who Dr. Nadolsky was debating was not known until recently when he realized he didn’t stand much of a chance one on one and was going to need to think outside the box. 

Dr. Nadolsky began by emphasizing, as Mr. Jakicic did later, that everyone (especially patients with obesity) needs to do some form of physical activity and exercise. He noted that we must meet patients where they are to get them the benefits of moving. Dr. Nadolsky reaffirmed that a combination of resistance training and aerobic training is optimal but, for this debate, remained firm in believing that resistance training is the more important of the two if we are going to split these hairs. That said, while this debate focused on fat loss, he conceded that aerobic training would win for weight loss over resistance training. But compared to newer interventions like pharmacotherapy and surgery creating a dramatic energy deficit, exercise is not very good for “weight loss,” per se, anyhow. Both Nadolsky and Mr. Jakicic cited data suggesting exercise intervention trials generally result in modest mean weight loss of 1% to 3% with that ≥150 minutes weekly of moderate-intensity aerobic training. 

Dr. Nadolsky also observed that large amounts of aerobic training helps but are very difficult to perform, which often creates an impenetrable barrier to patients with significant obesity in engaging in any aerobic activity. He also cited that, in recent pharmacotherapeutic trials (specifically Step-3), looking at semaglutide and intensive lifestyle intervention, including high amounts of aerobic activity compared to intensive lifestyle therapy alone, didn’t add much to the semaglutide arm in terms of weight loss when in the context of the other semaglutide trials where the lifestyle components were much less intense. He then pivoted from the specific topic of fat loss conceptually to treating obesity beyond weight in a more health-centric manner. Dr. Nadolsky cited concerns of significant loss of lean mass with such robust weight loss, which contributes to reduced overall energy expenditure making maintenance more difficult, cardiometabolic health, physical functioning, and quality of life. These concerns set the foundation for his final point that until some potential pipeline medications are available, resistance training is the only therapy that can mitigate the reduced lean mass when losing as much weight as is clinically targeted.

Mr. Jakicic began his rebuttal by reiterating that it was great having this discussion and bringing such positive attention to the inclusion of exercise and physical activity within obesity treatment paradigms. He also noted that while technically the topic is about fat loss and maintenance, he acknowledged Dr. Nadolsky’s points about lean mass retention are very valid. But he refocused and reminded the crowd that this was not technically the assignment. Mr. Jakicic went on to articulately review data showing that for fat loss and maintenance, aerobic training is superior to resistance training based upon the available evidence. He also pointed out that aerobic training has resulted in even better outcomes with higher intensity and increased volumes.

He showed how high-volume physical activity has even more robust and clinically relevant evidence for preventing weight gain and that those who have been able to maintain clinically important weight loss without medications or surgery engage in high volumes of physical activity, mostly some form of aerobic exercise. In comparison, there is minimal data specifically on resistance training, albeit acknowledging it is a lack of evidence rather than evidence against that possibility. Mr. Jakicic also reiterated that these studies are hard to do, especially comparing quality exercise regimens. Some examples are comparing aerobic versus resistance training showing minimal differences overall, even including lean mass but more visceral fat loss with aerobic exercise.

For the rebuttals, Dr. Nadolsky pointed out that some of the data supporting Mr. Jakicic's side included low-intensity walking, which should not necessarily count as aerobic training, and that this non-exercise physical activity could and should be added to any resistance plus aerobic training a patient can engage in. 

Mr. Jakicic did not disagree with that but felt it did not change his arguments for this specific fat loss question. When asked by the moderator about time efficiency, he noted that time spent in aerobic training utilizes much higher energy expenditure when compared to the same time spent in resistance training. Dr. Nadolsky replied, suggesting that if prescribed appropriately, resistance training optimized metabolically healthy muscle mass, and all the time spent performing non-exercise physical activity will have a higher energy expenditure. Mr. Jakicic responded with one example of a study in post-menopausal females where resistance training did not meaningfully lean mass retention or energy expenditure

Dr. Nadolsky pointed out that there are some studies contrary to that showing significantly preserved fat-free mass compared to aerobic training along with improved functional status and cardiometabolic risk factors

Not unexpectedly, their concluding remarks merged to some degree in that aerobic exercise, resistance training and their combination, along with non-exercise activities are important aspects for treating patients with obesity across the spectrum of adiposity-based complications. Dr. Nadolsky reiterated that resistance training includes cardiometabolic benefits and mitigate frailty, sarcopenia, and worsening bone mineral density. Mr. Jakicic conceded those benefits and suggested that there are many patients with such substantial physical limitations that they require some sort of resistance training just to eventually engage in any other physical activity. They both acknowledged the limitations of implementing physical activity and exercise regimens for many patients with Dr. Nadolsky argued that there are simple ways to incorporate resistance training at home without gym equipment, while Mr. Jakicic pointed out that slowly increasing the non-exercise physical activity can translate into an aerobic one in the future. He ended with a passionate plea to our professional organizations to advocate for insurance coverage of multidisciplinary teams that include certified exercise physiologists. With the help of exercise specialists, as recommended by the 2016 American Association of Clinical Endocrinology’s Comprehensive Care for Patients with Obesity Clinical Practice Guideline many of these barriers could be overcome. 

Who won? I obviously have a personal bias in favor of not only my younger brother, but also for resistance training. Mr. Jakicic, as always, did a fantastic job, essentially winning the assigned debate on aerobic training for fat loss. That said, I’m looking at the bigger picture of obesity management in this era of lifestyle therapy essentially shifted as adjunctive therapy to pharmaceutical and surgical weight loss. In that context, if a clinician must promote just one modality of exercise during active weight loss and long-term maintenance (again, not actually mutually exclusive), the benefits and feasibility of resistance training outweigh those of pure aerobic training.

Dr. Nadolsky has no conflicts of interest to report.

Image: vector juice / shutterstock

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