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WEIGHT SCIENCE, METABOLISM, BMI, AND SET POINT

Regulating our weight is more complicated than what we have been taught to believe. The diet and cosmetic industry want us to believe that we can control the size of our bodies through willpower and discipline. However, if we evaluate the research, we find is that the most consistent effect of weight loss at two years is weight gain. What the data actually shows is that the most predictive outcome of intentional weight loss is weight gain. Here is some data:

A meta-analysis of 29 studies on structured weight loss programs conducted in the U.S. found that participants regained 77% of their initial weight loss, on average, after 5 years (Anderson et al., 2001).
No study – exercise, diet, or surgery – has ever demonstrated long term maintenance of weight loss for any but a small minority (Mann et al., 2007, Miller et al., 1997).
Dieting triggers a reduction in leptin, which both increases appetite and decreases metabolism. And chronic dieting results in chronically less leptin release, which could easily explain why the majority of people with a history of dieting actually gain weight over time. (from the book Body Respect by Linda Bacon and Lucy Aphramor)

This can feel incredibly hard to believe since we have been been indoctrinated to believe that diets work (or "healthy eating" /lifestyle changes") and that weight gain is our fault. This is exactly what the diet and cosmetic industry wants us to believe so that we keep consuming their weight loss and "lifestyle" plans and products. After all, this multi-billion dollar a year industry is very invested in us continuing to hate our bodies, fearing fatness, and believing that we can control the size and shape of our bodies. It lines a lot of pockets.

BMI (Body Mass Index)

The Body Mass Index was introduced in the early 19th century by a Belgian man named Lambert Adolphe Jacques Quetelet. He was a mathematician, not a physician. He produced the formula to give a quick and easy way to assist the government in allocating resources (Devlin, 2009).

BMI was never intended to measure health, but as a way to measure the average weight of a population. The creator himself stated that it was NOT for use in individuals. Not only that, but the population measured was in no way representative of the diverse populations it’s being used on today. BMI was developed on a group of all men - no women. And because it was Belgium in the mid-1800s, it was mostly, if not all, white men.

Despite the widely held belief that a higher body mass index (BMI) causes poor health, empirical research does not support this link (Tylka, 2014). Research supports that people categorized as “overweight” actually tend to live longer than those considered “normal.” (Tylka, 2014) Factors such as exercise levels, nutrition, insulin resistance, weight cycling, and weight stigma often partially or fully explain the links between BMI and health. So, we cannot rely fully on a BMI score to determine if someone is "healthy" or "unhealthy."

Set Point and Metabolism

Bodies are diverse. Like trees, they come in all different shapes and sizes. Some are tall and thin, others are round and short. We don't expect pine trees to look like palm trees, nor should we expect that all humans should be thin. Research suggests that weight is genetically predetermined within a range (about a 10-20 pound range). Environmental factors play a role in our weight but not as significantly as genetics. The same goes for height. Our genetics determine a height range and environment can affect it in some circumstances though it is most significantly impacted by our genes. Most people generally accept that we can’t change our height but feel that weight is completely within our control. (Center for Clinical Interventions (2018).

Our bodies have a very complex system that is designed to maintain a "status quo" and keep our weight relatively stable (at our set point). When we lose weight, our bodies protect us by aggressively working to gain weight and bring us back to our set point. It will even RAISE the set point in order to protect us from dipping below it again in the future. This is why it is relatively easy to lose weight the first time one goes on a diet, but has so much trouble doing so in future attempts. The body now has a higher set point than it did at the onset of the diet. Set points often go up, but rarely go down. (Bacon, Health at Every Size)

The body does not know the difference between a diet and a time of famine or starvation. When the body is under nourished it will employ a variety of tactics to get back to a place of nourishment. Hormones will be released to make you feel hunger and increase your appetite. The body will heighten its sense of smell or taste making foods smell in order to make food more appealing. Craving more energy dense/high calorie foods is typical on a diet because the body can sense it is being deprived of calories. (Schwartz, 2001).

This change in set point and metabolism is what leads to weight cycling or "yo-yo dieting." Research shows that weight cycling results in increased inflammation, which increases the risks risk for many health problems (including diabetes and heart disease). The problem is that many studies blame the weigh itself - instead of the effects of weight cycling - for poor health outcomes seen in people on the higher end of the weight spectrum. Weight cycling is a serious hazard to health, yet diets continue to be pushed by doctors, trainers, coaches, therapists and the media, despite the fact that they fail 95% of the time.