Abstract
Long-term maintenance of weight loss requires sustained energy balance at the reduced body weight. This could be attained by coupling low total daily energy intake (TDEI) with low total daily energy expenditure (TDEE; low energy flux), or by pairing high TDEI with high TDEE (high energy flux). Within an environment characterized by high energy dense food and a lack of need for movement, it may be particularly difficult for weight-reduced individuals to maintain energy balance in a low flux state. Most of these individuals will increase body mass due to an inability to sustain the necessary level of food restriction. This increase in TDEI may lead to the re-establishment of high energy flux at or near the original body weight. We propose that following weight loss, increasing physical activity can effectively re-establish a state of high energy flux without significant weight regain. Although the effect of extremely high levels of physical activity on TDEE may be constrained by compensatory reductions in non-activity energy expenditure, moderate increases following weight loss may elevate energy flux and encourage physiological adaptations favorable to weight loss maintenance, including better appetite regulation. It may be time to recognize that few individuals are able to re-establish energy balance at a lower body weight without permanent increases in physical activity. Accordingly, there is an urgent need for more research to better understand the role of energy flux in long-term weight maintenance.
Highlights
Decades of research have shown that calorie-restricted diets of any macronutrient composition rarely result in permanent weight loss, and that long-term success rates for obesity treatment are low [1]
We focus on the concept of energy flux from a theoretical perspective, the components of energy flux, the impact of various modes and intensities of exercise on energy flux, and the potential advantages of achieving post-weight loss energy balance and weight maintenance at higher levels of energy intake and expenditure
The quickest viable approach to changing energy expenditure is through a change in physical activity energy expenditure (PAEE), the change in total daily energy expenditure (TDEE) is based on the magnitude of PAEE and the degree of behavioral and metabolic compensations that occur
Summary
Decades of research have shown that calorie-restricted diets of any macronutrient composition rarely result in permanent weight loss, and that long-term success rates for obesity treatment (apart from bariatric surgery) are low [1] In light of this phenomenon, the U.S National Institutes of Health sponsored a 2019 workshop titled, The Physiology of the Weight-Reduced State, for the purpose of addressing the issue of poor long-term obesity treatment outcomes. We focus on the concept of energy flux from a theoretical perspective, the components of energy flux, the impact of various modes and intensities of exercise on energy flux, and the potential advantages of achieving post-weight loss energy balance and weight maintenance at higher levels of energy intake and expenditure (high energy flux) This is not meant to be an exhaustive review, but rather to propose that based on evolutionary biology and high food availability in our current environment, high energy flux is inevitable, but how a high energy flux state is re-established following weight loss is critical to long term healthy weight management
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