Over hundreds and thousands of years, our ancestors developed adaptations to survive famine.  When faced with a dramatic shift in energy availability (i.e. decrease in food), the body responds with neurobiological, hormonal and metabolic changes.  So what does that mean?  The body’s physiological response to a decrease in food (dieting) means that…

1. Food cues in the environment become more salient.  You are more likely to notice food around you and you’ll also find it that much more appealing and appetizing – especially highly palatable foods (i.e. sweets, treats etc)

2. You feel hungrier.  There is an increase in hormones that trigger the sensation of hunger and a decrease in the hormones that make you feel full.

3. Your body becomes more efficient at using and storing calories.  In other words, your body immediately acclimates to running on fewer calories and as a result, it stores more as fat. 

If you think about it, this makes perfect sense if we were living in the wild.  In the face of famine, we’d be hustling to find food, driven by hunger and extreme focus/interest in finding something tasty and nourishing.  And as we’re searching for nourishment, our bodies would store up fat to get us through.

Many a frustrated dieter has experienced these mechanisms at play.  Unfortunately, most chalk it up to a lack of will-power or discipline.  Will-power and discipline have nothing to do with the bodies powerful survival mechanisms.

Diets sometimes do start off with success – a honeymoon period of sorts.  The early dieter may feel euphoric about the newfound experience of control and may revel in the early weight loss.  From a survival perspective, this makes some sense since our hunter-gatherer ancestors needed to manage their hunger as they focused on migrating to greener pastures where food sources would be more plentiful. But after this initial phase, the body’s protective mechanisms kick in and let us know that the honeymoon phase is over and we’d better get ourselves fed – and fast. 

Popular weight loss TV shows like “The Biggest Loser” have provided vivid illustrations of these neuroendocrine mechanisms at play. Following the completion of The Biggest Loser’s 16th season, more contestants than ever reported reverse effects—weight gains of up to 100 pounds post-production, some contestants reporting higher weights than ever before. Researchers have been evaluating these experiences to further their understanding of obesity and weight loss. While dramatic weight re-gain has been noted to be quite painful for the individual contestants, this controlled phenomenon of rapid weight loss and subsequent weight gain has proven to be a quality tool to researchers in understanding the failed mechanisms behind dieting and long-term weight loss. One such researcher, Kevin Hall, a scientist at a federal research center, initiated a project to measure what happened to Biggest Loser participants and others over a period as long as six years post-major weight loss.  Dr. Hall reports, it is “frightening and amazing” to see how hard the body fights back against weight loss. This kind of biologically-based obesity research has demonstrated that individuals are not to blame for post-diet weight gain, yet, so often, frustrated dieters shame and blame themselves.

More on the Biology of Weight Loss: Lessons Learned from “The Biggest Loser”

Metabolic Changes

Resting metabolism is a figure that determines how many calories one can burn when at rest. Dr. Hall’s research has demonstrated that deliberate weight loss resulted in a slowing of the resting metabolism when the diet came to an end. It’s notable that as the years went on and the Biggest Loser contestants gained back the weight they’d lost, their metabolisms did not recover. Dr. Hall reports that this phenomenon results in the need to take in even fewer calories than a typical person of the same size to maintain the weight loss—any additional calories would turn directly into fat. Understandably, this metabolic reset makes it extremely difficult to maintain weight loss.

Set Point

The body demonstrates its natural inclination to maintain a defined and specific weight range (set point) – a body’s “happy place” so to speak. The set point is a weight range that one’s body will maintain without much effort. This range may change over time with aging but science has demonstrated that the weight the body fights to maintain is largely out of the control of the individual. We’ve discussed how the body’s fight to maintain may be an evolutionary response.  But interestingly, genetic studies have demonstrated that weight is a heritable factor in the same way that height is largely heritable.  Given these evolutionary and genetic factors, a strong argument can be made to challenge the self-blame and criticism associated with “failed” dieting and post-diet weight gain.

The Impact of Leptin

Leptin is a hormone that controls hunger. Once an individual loses weight, their leptin levels will fall, causing hunger. In addition to a slower metabolism, plummeting levels of leptin were found in “The Biggest Loser” contestants at a follow up evaluation. While these contestants started out with normal levels of leptin, by the finale there was nearly none left at all. This research suggests that the only way to maintain weight loss is to tolerate a feeling of being hungry all the time. Novel research out of Pfizer is being undergone to test if researchers or clinicians will be able to train the brains of individuals who have lost weight, so they do not become ravenous for lack of leptin. Agents to suppress this feeling of hunger were deemed “desperately needed” by researcher Dr. Joseph Proietto out of Australia’s National Health and Medical Research Council, to assist these individuals in their goal of maintaining weight loss.

Bottom Line

While diets do work initially, when the body registers that food is scarce, neurobiological changes and gene expression typically win in the end.  The solution? The folks at feast-ed.org captured it beautifully: “We should eat in a way to convince our bodies that they no longer, and will never again, live with famine. That means never go on a reduced calorie diet.”

Moving On

At my3square, we’re acutely aware of how damaging dieting can be and guide our clients away from harsh and restrictive approaches to nourishment.  Instead, we encourage a flexible, intuitive and forgiving model of eating.  Within this model, we work to respond to our bodies’ natural hunger and fulness cues and build trust that we will get the nutrition we need.  The result is a more stable, healthier body and headspace and energy to devote to interests outside of diet and weight control.

References:

Guisinger, Shan (2012, March).  Dangers of Dieting: A Body Adapted to Famine.  Retrieved from http://www.feast-ed.org/news/253590/Dangers-of-Dieting-a-Body-Adapted-to-Famine.html

Kolata, Gina (2016, May).  After the Biggest Loser Their Bodies Fought to Regain Weight.  Retrieved from https://www.nytimes.com/2016/05/02/health/biggest-loser-weight-loss.html?mtrref=undefined&gwh=AF528F70B7BFE7E3E6C5E224009B1EFA&gwt=pay