Big fat lies about obesity

ASU professor says health risks of obesity have been exaggerated

Scale, apple, measuring tape


Editor's note: This story is being highlighted in ASU Now's year in review. Read more top stories from 2019.

An Arizona State University professor is challenging the long-held premise that obesity is the primary cause of many major weight-related health conditions and suggests focusing on healthy behaviors rather than the “lose weight, live longer” mantra repeated by most health professionals.

Glenn A. Gaesser, a professor of exercise science in the College of Health Solutions at ASU, recently underscored that viewpoint in a contrasting perspective he wrote in the journal Medicine and Science in Sports and Exercise. The topic: “Have the health risks of obesity been exaggerated?”

According to Gaesser, who has studied obesity for more than a quarter-century, that appears to be the case. “Health encompasses much more than a number on a scale,” Gaesser said. “We tend to get hung up on weight and that is a problem.”

ASU Now spoke to Gaesser about his recent perspective, his research and conclusions and how he fully expects that his stance will get mixed reactions.

Man in suit and tie smiling

Glenn A. Gaesser

Question: What is your definition of obesity and how should most people view this classification?

Answer: Obesity is challenging to define. The reason is that body fat within a population is characterized by a bell curve distribution, slightly skewed to the right (the heavy end). Where to draw the line between what is considered normal, and what is overweight or obese, is entirely arbitrary. That is the case for the current definition using the body mass index, or BMI. Anyone can easily go to an online BMI calculator, enter height and weight, and obtain their BMI. But BMI does not distinguish between body fat and lean tissue and does not provide any information about location of body fat. Fat located in the abdomen, particularly in the liver, has a far greater impact on health than total body fat. Most of our body fat is located subcutaneously, right under the skin. This fat is largely benign. Most importantly, BMI does not take into consideration lifestyle factors, such as exercise and diet, which have a far greater impact on health than any measure of body weight or body fat. 

It may seem logical to assume that people who exercise a lot and eat a healthy diet will naturally be thin. That is wishful thinking. Our weight, body fat and lean tissue mass are the result of a complex interaction of genes, behavior and environment. There are only so many things we can control.

Q: What motivated you to take a look at this issue and what type of reaction do you think you’ll get from your colleagues and health care community?

A: I have been examining the research in this area for about 25 years. It stemmed from two things. First, it became apparent to me that published research on the relationship between body weight or BMI and health outcomes had been, and still is, terribly misinterpreted. Second, I became aware of research which showed that virtually all the health problems typically associated with obesity could be improved or entirely normalized by changes in diet and exercise, even in the absence of weight loss. If obesity-related health problems could be improved independent of weight loss, this suggests that body weight itself is not the underlying cause. This requires a major paradigm shift in how we look at body weight and health conditions thought to be weight-related.

The reaction from colleagues and health professionals is always mixed. This has been true over the years. Many are just too quick to dismiss alternative viewpoints without critically examining the data. For example, when my first book, "Big Fat Lies: The Truth About Your Weight and Your Health," was published in 1996, a local publication did a feature on it. Four health professionals in my community — Charlottesville, Virginia, when I was at the University of Virginia — informed a reporter that my book was heresy. But all admitted that they had not read it. Therefore, these were not informed, open-minded or credible reactions.  

Q: What are the dangers of obesity? Why do people think it’s more harmful than it actually is?

A: This is a great question. I think most people tend to think that many — if not all — of the health problems of large people are entirely due to their body fat. But is this a fair assessment? The dangers of obesity are pretty much the same as those associated with poor diet and insufficient exercise. So you have to ask the question, “Are the health problems associated with obesity due to the body fat itself, or the lifestyle associated with it?” It’s straightforward to answer this question. Just have individuals with obesity increase their physical activity and change their diet and observe the results. These kinds of studies have been published all the time, and they show that obesity-related health markers improve with little, if any, weight loss. 

The health risks of obesity are also very much the same as the health risks associated with chronic weight cycling, or yo-yo dieting. So again, you have to ask the question, “Are the risks of obesity due to the body fat, or our obsessive efforts to get rid of it?” This is not trivial, because an obsessive focus on weight loss as the primary goal of “obesity treatment” could have unintended consequences.   

Q: But this message of harmful obesity would seem to come from the health community. Why has it been so widespread?

A: I think it’s widespread because it has been entrenched medical dogma for decades. The idea that a given body weight, or percentage body fat, is a meaningful indicator of health, fitness or prospects for longevity is one of our most firmly held beliefs, and one of our most dubious propositions. That’s not to say that obesity is entirely benign or that body weight is unimportant to health. It’s just that when you scrutinize all the relevant data it becomes apparent that the health risks of obesity, as well as the purported health benefits of weight loss, have been greatly exaggerated.

In the first place, there are a lot of large people who don’t have any health problems — they have what is considered a healthy obesity phenotype. Also, cardiovascular fitness virtually eliminates many of the health risks associated with obesity. Research has shown that fitness can be improved relatively quickly in people of all shapes and sizes, and the health benefits of improved fitness outweigh the health benefits of weight loss. Moreover, it’s easier to get a fat person fit than it is to get a fat person thin. Despite these well-established findings, cardiovascular fitness is not even mentioned in the most current weight management guidelines of the American Heart Association. Finally, removal of body fat by liposuction does not improve health markers such as blood pressure, blood fats and blood glucose control that are typically associated with obesity. These facts undermine the conventional wisdom on obesity and weight loss.

Q: What things should we be looking at other than weight to determine a person’s health?

A: Health encompasses much more than a number on a scale. It involves physical health as well as mental and emotional well-being. We tend to get hung up on weight, and that is a problem. The data on the benefits of regular physical activity and a healthy diet are consistent. We should focus on getting people to be more physically active and eating healthier foods. Our current approach tends to use diet and exercise as means to an end — weight loss. That is misguided. Healthy behaviors should be the goal. Some people may lose weight, some may not. But health improvements are largely independent of weight change.   

Q: One of your conclusions is that you are urging healthcare professionals to promote the benefits of a healthy lifestyle independent of weight loss and to increase fitness.  What are your recommendations?

A: The main reason for encouraging this paradigm shift is because our current focus on weight loss has been an abject failure. During the past 40 years or so, Americans have collectively undergone more than two billion weight loss attempts, mostly by dieting. Yet during this same time obesity prevalence has tripled. Not only has dieting not worked, it may have contributed to the increased prevalence of obesity.

The reasons for recommending a non-weight-loss-centered approach is that lifestyle behaviors such as diet and exercise are things over which we have considerable control. Weight loss, on the other hand, is something that may or may not happen as a result of lifestyle changes. It’s virtually impossible to predict how much someone will lose on a diet or exercise program, and the large variability can lead to frustration. But since the health improvements are largely independent of weight change, it makes sense to not focus on the weight. Moreover, there are no downsides to exercise and healthy eating. But yo-yo dieting, which is pretty much the norm in America, comes with considerable risks, and cannot be considered entirely benign. 

Q: Are you saying that we should just forget about obesity altogether?

A: No. I am not saying that we should be complacent about obesity or ignore it. But because the weight loss approach has not worked, and there are downsides to chronic yo-yo dieting, we need to embrace a new paradigm; one that does not stigmatize people for their size, but rather encourages everyone to engage in healthier behaviors for their own intrinsic value. Not everyone can be on the thin side of the bell curve for weight distribution. Fit and healthy bodies come in all shapes and sizes. And we need to acknowledge that the roads to a fitter and healthier body are wide enough for everyone. 

More Health and medicine


Three people talk on a bunch under a tree outside

Pilot program to address HIV care, intimate partner violence in Uganda

Editor's note: This is the second in a five-part series about ASU faculty conducting summer research abroad. Read about carbon collection in the Namib Desert.Uganda has one of the highest rates of…

Palo Verde Blooms

Hot and bothered: ASU event to discuss heat and health

Arizona State University's upcoming Health Talks event on July 18 will address how vulnerable populations are being impacted by heat across the world and how state governments are planning to deal…

A man stands with a microphone speaking to students in the foreground.

ASU students redesign 'Workstation on Wheels' for HonorHealth nurses

Going into this summer, Sheetal Jha, a biomedical engineering student, had specific expectations for the internship she would be participating in. “I was looking to gain hands-on experience in…