A Danish study indicates that vigorous-intensity exercise suppresses appetite, but the effect only lasts for a few months. The study is the first of its type to examine how long-term exercise affects appetite among individuals with overweight or obesity.
You might feel that your appetite declines when you increase the intensity of your workouts.
Actually, this may be true, and a new Danish study shows that 3 months of vigorous exercise training suppresses appetite.
This sounds like good news, but unfortunately, the appetite-suppressing effect of exercise does not seem to last and the study shows that the appetite suppression wanes after 6 months.
“The interaction between exercise, appetite and weight loss is very complex. We do not know what the long-term effects of exercise training on appetite regulation are. However, this study begins to lift the veil on the underlying mechanisms,” says Jonas Salling Quist, who carried out the study with other researchers as part of his PhD study at the Department of Biomedical Sciences, University of Copenhagen.
The study has been published in the Journal of Applied Physiology.
Last author Mads Rosenkilde was a postdoctoral fellow during the study, which was part of GO-ACTIWE, a randomized controlled trial led by Bente Stallknecht, Professor, Department of Biomedical Sciences, University of Copenhagen.
How exercise affects overweight people
The study is one of a series of studies in which the researchers from the University of Copenhagen have studied how exercise training affects various parameters, including appetite, weight loss and various biological markers in the blood, including the concentration of gastrointestinal hormones.
This randomized controlled trial randomly distributed 130 physically inactive women and men who were overweight or obese into four groups:
• a control group that continued their usual lifestyle;
• an exercise group that volunteered to commute by bicycle;
• a group that volunteered to perform leisure-time exercise at moderate intensity; and
• a group that volunteered to perform leisure-time exercise at vigorous intensity.
The participants in the three exercise groups were asked to wear a heart rate monitor during all sessions and were instructed to exercise five days a week and burn 320 calories per day for women and 420 for men.
Participants in the cycling group who could not burn the specified number of calories because they lived too close to their workplace were asked to make a detour to increase the distance. Conversely, participants who lived further away were asked to combine cycling and public transport.
“This was necessary to ensure that the energy expended during exercise was similar in the three exercise groups. This situation is somewhat artificial, and one must be aware of this when evaluating the results and the extent to which they can be generalized,” says Jonas Salling Quist.
Examining how much people ate
The researchers examined the participants’ appetite before the study started and 3 and 6 months later. Appetite was assessed based on self-rated appetite and the concentrations of biological markers in the blood associated with:
• eating a standardized breakfast;
• exercising on a stationary cycle; and
• how much the test participants ate during an ad libitum meal served at the end of the test day.
“Previous studies have primarily been shorter and without a control group. This is the first study to investigate the effects of different types of exercise over longer periods of time with repeated measurements and to compare the effects with a control group,” explains Jonas Salling Quist.
Vigorous exercise temporarily suppresses appetite
After 3 months, participants in the vigorous-intensity group reported less appetite after the standardized meal and after exercising on the stationary cycle compared with the control group. These participants also consumed food with 22% less energy at the subsequent ad libitum meal than the control participants did.
The appetite-suppressing effect was restricted to the vigorous-intensity exercise group.
The exercise intensity was not specified for the commuting participants, but they cycled on average at moderate intensity. The results therefore suggest that exercise must be vigorous to suppress appetite.
“Previous studies have shown that a single exercise session at vigorous intensity, such as on a stationary cycle, acutely reduces appetite and alters the concentration of gastrointestinal hormones in a way that indicates a biological appetite-suppressing effect. However, we did not find significant changes in biological markers that could explain the suppressed self-rated appetite and energy intake among our participants. When participants in our studies change from being physically inactive to suddenly exercising intensively, it affects their energy balance and leads to fat loss. However, the body does not seem to compensate for this by increasing appetite, as has been observed in diet-induced weight loss, for example,” says Jonas Salling Quist.
Weight loss declined after 3 months
In the same study, the researchers examined how the three different ways of exercising affected participants’ energy balance and fat loss.
All three groups lost body fat but mostly during the first 3 months, and then the fat loss declined from 3 to 6 months.
“We cannot conclude that there is an association between changes in appetite and fat loss in our study, but we cannot exclude an association either. However, our study suggests that something happens in the body when people with overweight and obesity exercise at vigorous intensity for 3 months and that this affects both appetite and weight. The participants continued to exercise from 3 to 6 months, but they compensated for the energy used in one way or another, and this could include small changes in energy expenditure outside the exercise sessions and in free-living energy intake,” says Jonas Salling Quist.
Further research to improve exercise programmes for people with obesity
After 6 months, the effects on self-rated appetite and ad libitum energy intake had disappeared, but concentrations of the GLP-1 hormone were higher in the fasting state and after the standardized breakfast among those exercising vigorously compared with the control group.
GLP-1 has an appetite-suppressing effect and therefore has an important role in regulating appetite, but the GLP-1 concentration apparently was not clearly associated with reduced self-rated appetite and energy intake.
Jonas Salling Quist says that the conclusions based on the study should be treated with caution because it was only exploratory. There is considerable variation in how exercise affects appetite and energy balance, and future studies should be dimensioned to take these factors into account.
“We can conclude that vigorous exercise appears to temporarily suppress appetite among people who were previously physically inactive and overweight or obese. The strengths of our study include the long trial period with repeated measurements and comparing the effects with a control group. Future studies should probe more deeply into understanding the complex interaction between exercise and appetite and how this knowledge can be used to create better exercise training programmes for overweight people, who are at risk of developing lifestyle-related diseases such as diabetes and cardiovascular diseases,” says Jonas Salling Quist.
“Effects of active commuting and leisure-time exercise on appetite in individuals with overweight and obesity” has been published in the Journal of Applied Physiology. Jens Juul Holst, a co-author, is a Professor and Scientific Director at the Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen.