Pennington Biomedical researchers recently investigated the body’s systems that regulate weight, investigating whether our bodies defend a set weight goal or whether our bodies operate within a wider range of tolerance before biological mechanisms are activated. The paper, titled “Models of body weight regulation in humans: insights into testing their validity,” which was recently published in Nature Reviews Endocrinology, examined competing models of body weight regulation and analyzed how energy intake and expenditure interact to maintain or disrupt weight stability.
The biological mechanisms of body weight regulation are not fully understood, so the researchers evaluated the theories behind the interaction of these mechanisms with the environment, as it ultimately determines body weight. The standard “set point” theory states that each person has a biologically set weight and that the body reacts strongly when weight changes are above or below this point.
The new theory – the “dual intervention point” – states that instead of a single body “set point”, each person has a lower and an upper limit, and that the body only reacts when body weight falls below the lower limit or rises above the upper limit. This model states that between these limits, weight is mainly influenced by lifestyle and environment, rather than the body defending itself against excessive increases or decreases in weight.
“Human body weight appears to be regulated by biological mechanisms that we still do not fully understand,” said Dr. Eric Ravussin, LSU Boyd Professor and the Douglas L. Gordon Chair of Diabetes and Metabolism at Pennington Biomedical. “Our analysis highlights the need to rigorously test state-of-the-art whether humans are advocating a single biologically defined set point or whether they operate within the upper and lower limits of intervention. In response to prolonged fasting or overfeeding, these models predict different metabolic and compensatory responses in people with low body weight compared to people with higher body weight.”
The importance of evaluating these determination and dual intervention theories may help explain why weight loss is so difficult for some people and not for others, why some people remain underweight even in today’s food-rich environments, and why body weight increases slowly but steadily for adults as they age. The main aim of the study is to understand how weight is regulated, which will influence strategies to prevent and treat obesity.
In the set point model, a fixed body weight defense point is assumed, with deviations eliciting compensatory responses such as changes in appetite or energy expenditure. The dual intervention model divides the responses into three categories: a strong biological defense against weight loss, a defense against weight gain, and a mid-range response that affects external influences such as behavior or the environment. This theory also states that the upper limit has drifted upward relative to human evolution.
The dual intervention theory suggests that the body likely has biological systems designed to maintain weight within a certain range. It is still unknown what the body intends to maintain by maintaining weight, such as body fat, muscle mass, stored carbohydrates, or even the energy status of cells.
“This analysis provides a useful framework for examining how biological and environmental factors interact to influence body weight,” said Dr. Jennifer Rood, Interim Senior Vice President and Chief Executive Officer of Pennington Biomedical; “By comparing fixed-point and dual-intervention models, the research contributes to a clearer understanding of weight stability and weight change. The work of Dr. Ravussin and colleagues reflects Pennington Biomedical’s continued commitment to advancing thoughtful, evidence-based approaches that can inform future clinical obesity research.”
