The Skinny on Dieting

We’ve all seen the infamous weight loss advertisements – the ones that claim to have finally found the magic diet that will absolutely make you lose weight. You can look at virtually any store’s checkout line to find dozens of diet plans endorsed by celebrities. However, most people don’t know that dieting can be counter intuitive to sustained weight loss. Evidence suggests that rapid weight loss, as evident in dieting, invokes an “emergency” homeostatic response by your brain to counter what it views as a threat of starvation.

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Dr. Sandra Aamodt, leading neuroscientist and best-selling author of Why Diets Make Us Fat: The Unintended Consequences of Our Obsession With Weight Loss, has spent her career studying the way our brains respond to food. As a self-reported “serial dieter” since the age of thirteen, she wanted to know if there were neurological explanations for why she seemed to regain weight after completing a diet. In her 2013 TED talk, “Why Diets Don’t Usually Work,” she attributes the phenomenon of regaining weight after dieting to something known as the “Set Point Theory.”

The Set-Point Theory asserts that a control system exists within the body to regulate weight at a particular “set-point,” or weight range of about ten to fifteen pounds. This range inherently differs from person to person, and is thought to be genetically driven. Similar to how a thermostat will regulate airflow to maintain a consistent temperature, the brain regulates body fat retention to maintain a certain weight range. However instead of temperature change, the stimulus is weight loss, and instead of changing air flow, the brain slows the metabolism and increases “hunger hormones” to retain more body fat.

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We often hear people use terms like “big-boned” or quip that they “have a fast metabolism” to explain their natural tendency to carry heavier or lighter amounts of weight. The set-point theory may be a causal explanation for these types of pre-disposed variations in weight. A number of hypotheses attribute the development of set-points to an evolutionary biological response to food scarcity. When our hunter-gatherer ancestors searched for food, they did not always know when their next meal would be, and thus relied on body fat retention to survive in times of famine.

Additionally, researchers have found that a body’s natural set-point can be replaced, or altered, when weight changes. However, Aamodt warns, it is much easier to increase a set point than to lower it. This has lead many to wonder if it actually may be more difficult to sustain weight loss after “resetting” one’s set point to a higher weight range. To test this, researchers conducted a study where they measured long-term changes in resting metabolic rate (RMR) among “The Biggest Loser” competitors. The 2004 reality t.v. show chronicled the months long weight loss journeys of contestants who were classified as overweight or obese. In the study, researchers took baseline RMR measurements of the sixteen contestants after their final weight loss.

Six years later, researchers reassessed the contestants. They found that all but one of reported regaining at least some of their pre-competition weight. Due to this weight regain, they expected to see a subsequent increase in RMR to compensate. However, among the participants that regained substantial weight, the investigators reported that their RMRs had remained the lowest. The fact that their RMRs did not rise proportionally to their regained weight meant that they were burning ~500 calories a day less than expected for their body composition and age. This evidence shows that “metabolic adaptation,” or slowed metabolism in response to weight loss, can persist for years despite regaining weight – a phenomenon that may be putting millions of Americans at a disadvantage.

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Weight Loss. Image Credit: Hamza Butt via Flikr

In fact, addressing increasing rates of obesity in Americans has been a top priority for public health officials for some time. Without successful health interventions, more and more people will be at risk for developing chronic diseases such as cardiovascular disease and type-2 diabetes. However, it seems that a cultural obsession with fad-diets may be putting those who wish to regain their health at an even greater disadvantage with even more excess weight gain. Knowing more about how the body reacts to different approaches to healthy weight management can help ensure that more people live longer, healthier, and happier lives.

Natalie Eldredge is an undergraduate student studying Public Health at the University of Georgia. In addition to studying public health, Natalie is an intern for the Southeastern Wind Coalition, a nonprofit organization that supports wind energy development in the southeast. In her free time, you can find Natalie at Taco Stand or watching documentaries with her roommates. Connect with her on Facebook or via email at natalie.eldredge@uga.edu.