Successful weight loss is commonly considered to be the net sum of calorie intake versus calorie expenditure. Although a seemingly simple notion, the prevalence of obesity in Australia continues to rise and is fast becoming our greatest health concern. A billion-dollar “dieting” industry exists, offering quick fixes, fads and big promises, however rarely delivers long-term, meaningful results. Numerous pills, products and celebrity-endorsed fad diets are focused on creating an energy deficit in order to achieve weight loss.
In theory, if weight loss were that simple, every person who had tried these products would have achieved some sort of meaningful weight loss; and each of these purveyors of weight loss products would slowly put themselves out of business. Even those who implement lifestyle changes under the guidance of appropriate experts find it difficult to maintain significant weight loss long-term. So why is this not working?
The concept of a body fat percentage ‘set-point’ is now better understood and provides an explanation as to why weight regain is so common and why sustained weight loss is so difficult. This theory is of particular importance for people who have serious weight issues (BMI above 35). Body fat percentage is tightly regulated to ensure we have adequate energy stores to survive in times of increased stress, such as illness. The human body does not like change, and prefers to maintain a state of homeostasis (stable balance). It is for this reason that multiple physiological mechanisms override our effort to lose weight, and ensure our weight is maintained.1 This weight is known as our ‘set-point’ and is different for everyone.1 Patients with obesity have an elevated set point, which can be attributed to many factors.1 Genetics, environmental factors and lifestyle habits all have a role in causing an abnormally elevated set point1. Furthermore, once elevated various physiological factors fight to keep it there.1
Neural and hormonal factors are responsible for sustaining an elevated set point. The hypothalamus is an area of the brain responsible for appetite control and regulation of metabolic rate. In response to diet-induced weight loss the hypothalamus signals to increase appetite and decrease metabolism, in order to prevent further weight loss.1 In addition to this neural action, hormonal regulation also acts to inhibit weight loss. Studies have shown that even one year after initial weight loss, circulating levels of appetite regulators that promote weight gain, such as the hormone ghrelin for example, are higher compared to baseline measures before weight loss.2
For long-term weight loss, it is clear that interventions must not only create an energy deficit but also act to modify the body fat percentage set point. Modern bariatric surgery is an effective treatment in which many patients are able to do just this and is therefore increasingly associated with successful outcomes.
It is a common misconception that bariatric surgery works only by ensuring an energy deficit, through both restrictive and malabsorptive means. It is now understood that bariatric surgery also influences the set point through hormonal changes post-surgery.3 For example, studies have shown that following a meal, post-surgery patients have increased levels of peptides that promote satiety.3,4 The gastric bypass procedure in particular has been associated with improved blood sugar control through heightened insulin response.4 This is certainly an exciting area of research, and more investigations are needed to better understand these pathways. To achieve the best outcomes for patients a multidisciplinary approach is critical. Surgery is effective in addressing the physiological mediators of obesity, however it does not address the social aspects of eating, or a strong dieting mentality that may have developed over many years of weight loss attempts. Regular follow-up with a dietitian and psychologist aids in supporting patients along their weight loss journey. The causes of obesity are multifactorial and complex. With a holistic health care team approach, bariatric surgery is a successful and sustainable weight loss option for many patients.
References:
- Kaplan L, Seeley R, Harris J. Myths associated with obesity and bariatric surgery: Myth 1: Weight can be reliably controlled by voluntarily adjusting energy balance through diet and exercise. Bariatric Times. 2012;9(5):12-13.
- Sumithran P, Prendergast L, Delbridge E, Purcell K, Shulkes A et al. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med. 2011;365(17): 1597-1604.
- Kaplan L, Seeley R, Harris J. Myths associated with obesity and bariatric surgery: Myth 2: Bariatric surgery induces weight loss primarily by mechanical restriction and nutrient malabsorption. Bariatric Times. 2012;9(5): 12-13.
- Le Roux C, Aylwin S, Batterham R, Borg C, Coyle F et al. Gut hormone profiles following bariatric surgery favor an anorectic state, facilitate weight loss, and improve metabolic parameters. Annals of Surgery. 2006;243(1): 108-114.
