Energy flux: staying in energy balance at a high level is necessary to prevent weight gain for most people

Abstract

Energy flux, the rate of energy conversion from absorption to expenditure or storage, is a critical component of understanding weight management. Individuals who maintain body weight over time have common characteristics including a relatively high level of physical activity and minimal changes in body composition, muscle mass and metabolic rate. A higher state of energy flux resulting from high energy expenditure may provide for a greater ‘sensitivity’ between energy intake and expenditure. This sensitivity stabilizes body weight by enhancing reciprocal compensation among these components with changes in eating or activity. The energy balance framework suggests that a higher level of energy expenditure requires higher energy intake to maintain body mass. Maintaining energy balance at a higher caloric intake and expenditure should be a more successful long-term strategy for weight maintenance than reduced consumption or extreme caloric restriction at a low level of energy expenditure (a low energy flux) and improve intervention effectiveness for sustainable methods for body weight stability.

Keywords:

• body composition
• energy balance
• fatness
• obesity
• physical activity
• weight loss

Financial & competing interests disclosure

GA Hand received non-restricted research funding and travel grant from The Coca Cola Company and a travel grant from International Life Sciences Institute. RP Shook received a travel grant from the Coca Cola Company. JO Hill received research support from the Coca Cola Company and the American Beverage Association. JO Hill is on the advisory board for McDonalds, General Mills, Curves, Consumer Goods Association, Calorie Control Council, International Food Information Council and McCormick Science Institute. JO Hill is a consultant for Walt Disney, has equity in Gelesis and Active Planet and is on the Board of Directors for International Life Sciences Institute and Livewell Colarado. SN Blair is the principal investigator on projects supported by unrestricted research grants from The Coca Cola Company to the University of South Carolina. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Key issues

• Energy balance theory, based on the law of conservation of energy, defines the relationship among energy intake, expenditure and storage. It provides the framework to understand the determinants of body weight change.

• Energy flux, the rate of energy conversion from calories consumed, is a critical and relatively unstudied component of energy balance theory.

• While limited, data from animal and human studies suggest that there is a range of energy flux at which the sensitivity of intake and expenditure matching is optimally maintained.

• The ‘sensitivity range’ of energy balance suggest that maintaining a stable weight is more easily achieved when the balance of intake and expenditure is at a high flux.

• During periods of low energy expenditure, energy storage (weight gain) is a biologically viable means for the body to maintain a high energy intake.

• Physical activity, a significant component of total energy expenditure and a determinant of energy flux, is usually higher in lean individuals and shows an inverse relationship with weight gain over time.

• Resting metabolic rate is the predominant component of daily energy expenditure in most healthy individuals. Changes in resting metabolic rate result from changes in body mass and body composition. Exercise energy expenditure correlates positively with lean tissue mass.

• Energy flux is a critical component to be considered in the development of effective weight management interventions.