ESPE Yearbook of Paediatric Endocrinology

To read the full abstract: J Clin Endocrinol Metab 2019;104(10):4481–91. PMID 31305927.

In this randomized crossover study, 16 healthy adults were examined in a metabolic chamber during four different conditions of energy balance (ad libitum energy intake, zero energy balance, 25% caloric restriction, and 125% overfeeding) and at three levels of energy turnover (ET): Physical activity level (PAL) 1.3 low, 1.6 medium, and 1.8 high ET, achieved by walking on a treadmill.

Interestingly, compared to high ET, low ET was associated with increased subjective appetite ratings assessed by visual analog scales, a higher desire to eat and a positive energy balance during subsequent ad libitum food intake. Low ET resulted also in a decrease in circulating GLP-1 and an increase in ghrelin. On the other hand, high ET was associated with decreased appetite, high GLP-1 serum levels and low ghrelin serum levels.

The control of body weight is achieved by influencing energy intake (EI) through food intake and energy expenditure (EE) through physical activity. Energy turnover (ET) consisting of EI and EE should be kept in a balance. Easy in thinking and from a simple teleological point of view, endocrine signals, e.g. from adipose tissue and the gastrointestinal tract, report the current state of EB to key brain regions and EE should directly impact the control of appetite and EI. However, it has been hypothesized that the control of body weight might be easier in conditions when energy turnover (ET) is high as compared to conditions with low ET.

This study in healthy individuals now demonstrates two important physiological results: i) appetite is regulated more effectively at a high level of ET and ii) high level physical activity not only helps to control body weight by increasing energy expenditure but results impressively in an improved appetite sensation. Therefore, these results contrast with some paradigms related to the concept of body weight control.

There have been observations in the past – and every one of us reflecting on their lifestyle and doing more exercise may have noticed this subjectively – indicating that there might be an asymmetric control of EB with a ‘regulated zone’ at high EE and an ‘unregulated zone’ at low EE (1).

In addition, it has been hypothesized that there exists an ‘exercise-induced anorexia’ mediated by lowered concentrations of acylated ghrelin and elevated concentrations of GLP-1 and PYY [reviewed in (2)].

This study is the first to prove an asymmetric control of appetite, with a high ET that improves appetite control. The study was even able to show that this is probably causally associated with increased GLP-1 and decreased ghrelin concentrations independent of EB.

It is worth noting that the investigators chose low-intensity physical activity to increase the PAL. This simulates daily activities without the effects of vigorous exercise on metabolism and avoids fatigue or pain in persons with very low fitness. For sure, increasing physical activity in daily life may be easier for most people than reducing food consumption while maintaining an equal EB.

References:

1. Blundell JE, Gibbons C, Caudwell P, Finlayson G, Hopkins M. Appetite control and energy balance: impact of exercise. Obes Rev. 2015;16 (Suppl 1):67–76.

2. Stensel D. Exercise, appetite and appetite-regulating hormones: implications for food intake and weight control. Ann Nutr Metab 2010;57 (Suppl 2):36–42.