To Tackle Obesity, Up Fitness and Activity or Lose Weight?

Mitchel L. Zoler, PhD

October 21, 2021

Obesity interventions would be more effective at preventing premature mortality if they focused less on weight loss and more on increased physical activity and improved cardiorespiratory fitness, conclude a pair of researchers in a recent review.

The authors promote a "weight-neutral approach to treating obesity-related health conditions," which they say is "as or more effective than a weight-loss centric approach."

One expert agrees. "The obsession with the bathroom scale as the primary determinant of treatment efficacy when managing obesity is just not right," Robert Ross, PhD said in an interview.

"It masks the tremendous health benefits of improved fitness regardless of obesity. If you increase fitness, you improve outcomes even when people don't lose weight," noted Ross, a researcher in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario, Canada.

However, this proposition reprises a long-standing gulf between two schools of thought on obesity intervention.

One indication of the divided sentiment came in another expert review, published just days later, that strongly calls for weight loss of at least 15% of starting body weight as the primary intervention goal for most patients with obesity and type 2 diabetes. (According to 2020 statistics from the US Centers for Disease Control and Prevention, more than 60% of US adults with diabetes are obese.)

However, some question whether it must be all one, or the other, when obesity management could instead combine these approaches and simultaneously promote weight loss, increased activity, and improved fitness.

"It only muddies the water to dichotomize this as either weight management or activity and physical fitness," observed Scott Kahan, MD, an obesity specialist and director of the National Center for Weight and Wellness in Washington, DC.

Weight-Neutral "Is the Way to Go"

"The most significant new information [in the review] is the direct comparison of the magnitude of mortality risk reduction associated with weight loss compared with increasing fitness, physical activity, or both," said Glenn A. Gaesser, PhD, the first author of the new review and professor of exercise physiology at Arizona State University in Phoenix.

"The results are quite clear: increasing fitness, physical activity, or both are associated with greater mortality reductions than intentional weight loss. We argue that a weight-neutral approach to treating obesity is the way to go."

The data call "into question the widely perceived notion of 'lose weight, live longer,'" resulting in a "paradigm shift," Gaesser said in an interview.

"There are no downsides to exercise, but there are significant downsides to weight loss, especially when it is inevitably followed by weight regain, which gives rise to the undesirable 'weight-loss futile cycle'," he added.

No Simple, Single Solutions

Kahan said, however, that comparison of the effects of weight loss with the effects of increased activity and fitness on mortality is inherently problematic.

"It's hard to make definitive conclusions from observational studies," he cautioned, noting that the data cited in the review of activity and fitness compared with weight loss are generally "estimations" that carry a "lot of cloudiness."

Kahan also takes issue with the premise detailed in the review that targeting reduced weight and implementing healthful and evidence-based approaches to try to achieve it are bound to fail and have frequent adverse consequences.

"Managing weight in a reasonable, patient-centered, thoughtful way is a standard and central part of long-term health," he said in an interview.

He did concede, however, that the US weight-loss landscape is awash with hucksterism that takes advantage of many patients, and he cautioned against approaches that focus on weight loss at all costs and as a pathway to selling products.

"But staying focused on activity and not pay attention to healthy eating is extreme," he said, reemphasizing that obesity management is not a simple intervention with a single solution.

Not the First Time

This is not the first time that Gaesser, and others, have published articles promoting a pivot away from weight loss as the primary goal of obesity interventions. In 2015, Gaesser and colleagues published an evidence review that gave this recommendation for managing people with obesity: "We propose that the proxy for health improvements should not be weight loss but instead improvements in cardiometabolic parameters, functional status, and fitness."

Gaesser's latest review also acknowledges similar recommendations from others, including Ross, who said it's nothing new to conclude that increased fitness and activity in the absence of weight loss is not failure.

"It's something we've promoted for decades," but "it's not understood and acted on in clinical settings, and that's unfortunate," he said.

More than a decade ago, Ross and his coauthor wrote in a published review that "a monolithic focus on weight loss as the only determinant of success for strategies that aim to reduce obesity is not justified and, more importantly, eliminates opportunities to focus on lifestyle behaviors that are associated with benefit across a wide range of health outcomes."

And an effective intervention that focuses on activity and fitness means that, at the least, patients should not gain weight, and they may lose weight as a side benefit, he stressed.

"We always advocate a balanced diet, so that people do not gain more weight."

Ross also highlighted the usefulness of measuring fitness as an alternative to recording weight to track the response by patients with obesity to various interventions. Ross recommends nonexercise prediction equations for routine practice to easily estimate cardiorespiratory fitness, an approach detailed in a 2016 statement from the American Heart Association (AHA) by a writing panel chaired by Ross.

The AHA statement notes that "not including cardiorespiratory fitness measurement in routine clinical practice fails to provide an optimal approach for stratifying patients according to risk."

The AHA also advises that "routine estimation of cardiorespiratory fitness in clinical practice is no more difficult than measuring blood pressure," and details ways of incorporating this into routine clinical assessment.

Gaesser and Kahan have reported no relevant financial relationships. Ross has been an advisor to the Canadian Sugar Institute.

iScience. Published online September 20, 2021. Full text

Mitchel L. Zoler is a reporter for Medscape and MDedge based in the Philadelphia area. @mitchelzoler

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