Eat More, Do More
The Importance of Energy Flux in Weight Management
Why “eat less move more” is incomplete advice.
If you’ve ever gone to Beyonce’s internet looking for tips and tricks to lose weight, you’ve probably encountered lots of advice usually saying something like “eat less, move more” or “calories in vs. calories out.” And while energy balance (intake vs. expenditure) is crucial for determining rates of adipose (fat) deposition (storage) and oxidation (usage), there’s more nuance than simply consuming fewer calories than you use. Many of my clients have heard me say (usually to their dismay) that they are not eating enough to support fat loss. The reason? Energy flux.
Energy flux is the rate at which energy flows in and out of a system. In the human body, this includes the energy we consume from food and drinks, the energy we expend through physical activity and bodily functions, and the energy that is stored as body fat. You can also think about energy flux as the total sum of energy intake and expenditure.
Energy balance is the difference between the energy we consume and the energy we expend. When we are in energy balance, the amount of energy we consume is equal to the amount of energy we expend, and our body weight remains stable. If we consume more energy than we expend, we’re in a positive energy balance and we will gain weight (usually as fat). If we consume less energy than we expend, we are in a negative energy balance and we will lose weight. We refer to this as “calories in vs. calories out.”
Energy flux is different from energy balance in that it is a measure of the rate of energy flow, while energy balance is a measure of the difference between total energy intake and expenditure. Energy flux is important for understanding how the body uses energy and how to create a calorie deficit for weight loss.
An emerging body of research shows that the human body will find strategies to maintain a state of high flux, and that weight gain may be a mechanism for increasing energy expenditure. More body mass = more energy expenditure (it “costs” more to maintain a larger body). For example, an increase in daily energy intake above the equivalent energy expenditure will result over time in energy storage and weight gain. The weight gain results in an increased resting metabolic rate (RMR) and increased energy cost of moving the greater mass. The increased rate of expenditure will eventually reach an equivalent level of the higher energy intake (thus reaching energy balance), but at an overall increase in intake and expenditure (Swinburn et al.).
This model suggests first that energy balance, and maintaining a stable weight is more easily achieved in a state of high flux. Second, a high energy flux can be achieved by matching a high energy intake with equivalent high energy expenditure (moving more), or by increasing energy stores (gaining weight). Take note that these two characteristics suggest that the body’s metabolic system was designed to maintain a high energy flux, and increasing energy stores is a viable mechanism to achieve this. An extensive body of research indicates that multiple and redundant mechanisms regulate the ‘drive’ for energy intake (Blundell et al. 2012).
A study of 10 older adults (mean age 66 years) found that individuals with higher energy flux had a higher RMR (Bell et al.). In addition, a study of 31 postmenopausal women aged 49–72 years found a positive correlation between high exercise energy expenditure and resting energy expenditure (Froehle et al. 2013). An analysis of 430 healthy young adult men and women showed that over a 10-day period of observation, when corrected for body weight, the lean participants displayed the highest daily energy intake, expenditure, RMR, and physical activity energy expenditure (Hand et al. 2014).
Numerous studies have demonstrated improvements in metabolic parameters following an increase in energy flux.
In one study, 52 obese men were randomly assigned to one of four groups: diet-induced weight loss, exercise-induced weight loss, exercise with calorie compensation to maintain weight, and control and were observed for 3 months. Body weight decreased by 8 % in both weight loss groups; cardiovascular fitness improved by approximately 16 % in the exercise groups. Although total fat decreased in both weight loss groups, the reduction was 1.3 kg greater in the exercise induced weight loss group than in the diet-induced weight loss group. There was also a significant decrease in abdominal and fat in the exercise with calorie compensation group (Ross et al. 2000).
A similar study randomized 44 premenopausal women with abdominal obesity to the same four groups. Reduction in total and abdominal fat within the exercise weight loss group was greater than within all other groups. The reduction in total and abdominal fat within the diet weight loss and exercise without weight loss groups was greater than within controls but not different from each other. Insulin sensitivity improved in the exercise weight-loss group (Ross et al. 2004).
In another study of 24 obese, older subjects (aged 50–80 years of age), the exercise weight-loss group showed an increase in insulin-stimulated suppression of glucose Ra, a measure of hepatic insulin sensitivity, almost three times greater than that of the dietinduced weight-loss group. The exercise group with calorie restriction also showed substantial increases in fasting glucose production (Coker et al. 2009)
These findings suggest that a high energy flux maintained through participating in exercise can improve an individual’s metabolic profile with or without changing body weight. A combination of resistance training and aerobic exercise appears to be most effective in improving glycemic parameters (Cuff et al. 2003, Lee et al. 2012).
An understanding of energy flux is crucial to the design of interventions to combat obesity. Reducing obesity requires modifying both energy intake and energy expenditure. High expenditure allows for a greater consumption of calories and potentially provides a means to maintain balance and weight at a manageable daily caloric intake. Interventions that do not address both energy expenditure and intake tend to be unsuccessful in the long term (Ebbeling et al. 2002).
Recent studies have demonstrated that an understanding of energy flux can not only enhance weight loss but also improve metabolic parameters. Interventions that increase physical activity promote the reduction of visceral adipose tissue and hepatic insulin resistance, even when calorie intake is increased. In fact, high energy flux, i.e. high caloric intake and expenditure, appears to be an optimal strategy for maintaining weight while improving metabolic strategies (Hand et al. 2014).
Hand, G. A. and Blair, S. N. (2014). Energy flux and its role in obesity and metabolic disease. European Endocrinology, 10(2), 131. https://doi.org/10.17925/ee.2014.10.02.131
Swinburn BA, Sacks G, Lo SK, et al., Estimating the changes in energy flux that characterize the rise in obesity prevalence, Am J Clin Nutr, 2009;89:1723–8.
Blundell JE, Caudwell P, Gibbons C, et al., Role of resting metabolic rate and energy expenditure in hunger and appetite control: a new formulation, Dis Model Mech, 2012;5:608–13.
Bell C, Day DS, Jones PP, et al., High energy flux mediates the tonically augmented beta-adrenergic support of resting metabolic rate in habitually exercising older adults, J Clin Endocrinol Metab, 2004;89:3573–8.
Froehle AW, Hopkins SR, Natarajan L, et al., Moderate to high levels of exercise are associated with higher resting energy expenditure in community-dwelling postmenopausal women, Appl Physiol Nutr Metab, 2013;38:1147–53.
Hand GA, Shook RP, Jaggers JR, et al., Determinants of energy balance: differences related to body weight and body composition, Circulation, 2013;127:AP022.
Ross R, Dagnone D, Jones PJ, et al., Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial, Ann Intern Med, 2000;133:92–103.
Ross R, Janssen I, Dawson J, et al., Exercise-induced reduction in obesity and insulin resistance in women: a randomized controlled trial, Obes Res, 2004;12:789–98.
Cuff DJ, Meneilly GS, Martin A, et al., Effective exercise modality to reduce insulin resistance in women with type 2 diabetes, Diabetes Care, 2003;26:2977–82.
Lee S, Bacha F, Hannon T, et al., Effects of aerobic versus resistance exercise without caloric restriction on abdominal fat, intrahepatic lipid, and insulin sensitivity in obese adolescent boys: a randomized, controlled trial, Diabetes, 2012;61:2787–95.
Ebbeling CB, Pawlak DB, Ludwig DS, Childhood obesity: publichealth crisis, common sense cure, Lancet, 2002;360:473–82.
