Research: Losing weight just by exercising more is often disappointing

Geschatte leestijd: 5 minuten Losing weight by simply increasing physical activity often disappoints. Research shows that we may compensate for the extra exercise by eating more and being less active at other times.

Losing weight by increasing physical activity?

Especially in articles about cardio, we often explain that the kitchen is the quickest way to lose weight, not the treadmill. Losing weight is achieved by consuming more energy than you expend. The majority of your energy intake, typically about 80 percent, is used for essential processes. A relatively small portion is used for your daily activity. So, if you double your exercise and double your food intake, you’ll gain weight. But even when taking this into account, weight loss through additional exercise often seems disappointing in studies. In various studies, the result of the additional energy expenditure appears to be less than expected [1]. In practice, extra exercise often does not lead to an energy deficit, and when it does, this deficit often yields less results than expected.

The commonly observed low levels of weight loss have led to several questions regarding the effects of regular exercise on body weight and the reasons why the energy deficit appears to be smaller than predicted. D.M. Thomas, Montclair State University

Why don’t you lose much weight by exercising more?

In 2013, researchers from Montclair State University attempted to answer this question. They collected and compared previous studies on this topic – studies where the effect of increased exercise on weight was lower than expected. The researchers posed three questions:

• What causes the energy deficit?
• What explains the difference between the energy deficit caused and the expected effect on weight?
• What effect does exercise have on body composition and how does this affect metabolism?

In the table below, you can see the results. Look at the differences between Energy Imbalance and Prescribed exercise. The latter is the number of daily calories that should be burned through exercise. The energy imbalance shows any resulting energy deficit. In most cases, the additional expenditure shows a higher number than the resulting deficit. In extreme cases, we even see a difference of 300 to 400 calories!

From Table 1 we observe that for the majority of studies, the magnitude of achieved energy imbalance was consistently lower than prescribed energy expenditure from exercise. Because the additional energy expenditures through physical activity were rigorously supervised, the low magnitude of energy imbalance must have been a result of metabolic adaptation, decreased non-exercise activity or a compensatory increase in Energy Intake

Compensating/neutralizing extra exercise by eating more

There are three presumed ways in which we compensate for extra exercise, consciously or unconsciously. One of those ways is by increasing energy intake. Several studies indicate that people eat more when they exercise more frequently. The more they train, the greater the degree of compensation. Additionally, it appears that lean individuals have a greater tendency to compensate for an energy deficit caused by exercise with extra food than overweight individuals [2,3]. You might think this is a conscious choice. After all, slim people do not aim to lose weight. It could also be the body’s own protection mechanism, which intervenes earlier when someone with little body fat expends a lot of energy. In a recent similar study on mice, this compensatory behavior by eating more was not observed [4].

Compensating for extra exercise by being less active at other times

In mice, however, we did observe the second possible form of compensation: being less active at other times. It’s great if you decide to become more active by going for a run a few times a week. But what’s the point if you’re exhausted on the couch for the rest of the day? There are a few studies concluding that this doesn’t often happen, except among the elderly [5,6]. However, you should consider how other activity was measured. This is usually done with accelerometers, which is not a very accurate way to measure activity. In the recent study with mice, the researchers tried to address this by measuring activity in a very different way. They used infrared rays to measure movements. The mice did not eat more when they ran more on the treadmill. However, they were less active at other times. As a result, the mice had only a small energy deficit. A deficit that would be 45% larger if they did not reduce their activity in their cage.

1. Thomas DM, Bouchard C, Church T. Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis. Obesity reviews : an official journal of the International Association for the Study of Obesity. 2012;13(10):835-847. doi:10.1111/j.1467-789X.2012.01012.x.
2. Woo R, Pi-Sunyer FX. Effect of increased physical activity on voluntary intake in lean women. Metabolism. 1985;34:836–841.
3. Woo R, Garrow JS, Pi-Sunyer FX. Voluntary food intake during prolonged exercise in obese women. Am J Clin Nutr. 1982;36:478–484.
4. Reduced Nonexercise Activity Attenuates Negative Energy Balance in Mice Engaged in Voluntary Exercise Daniel S. Lark, Jamie R. Kwan, P. Mason McClatchey, Merrygay N. James, Freyja D. James, John R.B. Lighton, Louise Lantier, David H. Wasserman Diabetes Mar 2018, db171293; DOI: 10.2337/db17-1293
5. Alterations in energy balance with exercise. Westerterp KR Am J Clin Nutr. 1998 Oct; 68(4):970S-974S.
6. Long-term effect of physical activity on energy balance and body composition. Westerterp KR, Meijer GA, Janssen EM, Saris WH, Ten Hoor F Br J Nutr. 1992 Jul; 68(1):21-30.
7. Ballor DL, Poehlman ET. A meta-analysis of the effects of exercise and/or dietary restriction on resting metabolic rate. Eur J Appl Physiol Occup Physiol. 1995;71:535–542.
8. Ross R, Janssen I. Physical activity, total and regional obesity: dose-response considerations. Med Sci Sports Exerc. 2001;33(6 Suppl):S521–S527. discussion S528–S529.
9. Speakman JR, Selman C. Physical activity and resting metabolic rate. Proc Nutr Soc. 2003;62:621–634.
10. Westerterp KR, Meijer GA, Schoffelen P, Janssen EM. Body mass, body composition and sleeping metabolic rate before, during and after aerobic training. Eur J Appl Physiol Occup Physiol. 1994;69:203–208.
11. Westerterp KR. Pattern and intensity of physical activity. Nature. 2001;410:539.

An important difference between humans and mice is that humans use a calendar and have a daily schedule. The fact that you go for a run for an hour in the evening does not mean you have to bike less to work. The supermarket doesn’t get closer, and you still have to climb the same stairs at home or in the office. So, the question is how much opportunity we actually have to compensate for training by reducing activity at other times. Also, consider that compared to other mammals, including rodents, humans are quite inactive. If you’re already minimally active, there’s little to compensate for by moving even less.

Compensation by lower metabolism

A third possibility is that the body itself decides to use energy more efficiently when an energy deficit occurs. Training in general, and cardio in particular, should not have a lowering effect on your resting metabolism. In fact, when it does not lead to an energy deficit, it can actually increase metabolism [7-11]. However, the energy deficit caused by training can have a negative effect here. A large energy deficit can lead to a decrease in muscle mass. As a result, your body burns less energy. However, this is not due to the training, but the energy deficit. A diet that leads to the same energy deficit can cause a greater decrease in your fat-free mass and therefore also a greater decrease in your resting metabolism.

Conclusion

Personally, I’m not in favor of exercise as the primary way to lose weight. For that, I would always advise getting your diet in order first. Prioritize achieving an energy balance or deficit in your diet. That doesn’t mean that physical activity is unnecessary. On the contrary, physical activity offers many other benefits besides potential weight loss. If you’re using your diet to lose weight, you can, for example, choose strength training instead of cardio to maintain or gain as much muscle mass as possible. Does cardio have no place? Yes, but mainly for what it’s intended. To train the cardiovascular system, from which it derives its name (cardiovascular training). So:

• Diet to manage weight
• Strength training to gain or maintain muscle mass
• Cardio for overall health and well-being

The best thing is, of course, that you can combine all three.

References

1. Thomas DM, Bouchard C, Church T. Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis. Obesity reviews : an official journal of the International Association for the Study of Obesity. 2012;13(10):835-847. doi:10.1111/j.1467-789X.2012.01012.x.
2. Woo R, Pi-Sunyer FX. Effect of increased physical activity on voluntary intake in lean women. Metabolism. 1985;34:836–841.
3. Woo R, Garrow JS, Pi-Sunyer FX. Voluntary food intake during prolonged exercise in obese women. Am J Clin Nutr. 1982;36:478–484.
4. Reduced Nonexercise Activity Attenuates Negative Energy Balance in Mice Engaged in Voluntary Exercise Daniel S. Lark, Jamie R. Kwan, P. Mason McClatchey, Merrygay N. James, Freyja D. James, John R.B. Lighton, Louise Lantier, David H. Wasserman Diabetes Mar 2018, db171293; DOI: 10.2337/db17-1293
5. Alterations in energy balance with exercise. Westerterp KR Am J Clin Nutr. 1998 Oct; 68(4):970S-974S.
6. Long-term effect of physical activity on energy balance and body composition. Westerterp KR, Meijer GA, Janssen EM, Saris WH, Ten Hoor F Br J Nutr. 1992 Jul; 68(1):21-30.
7. Ballor DL, Poehlman ET. A meta-analysis of the effects of exercise and/or dietary restriction on resting metabolic rate. Eur J Appl Physiol Occup Physiol. 1995;71:535–542.
8. Ross R, Janssen I. Physical activity, total and regional obesity: dose-response considerations. Med Sci Sports Exerc. 2001;33(6 Suppl):S521–S527. discussion S528–S529.
9. Speakman JR, Selman C. Physical activity and resting metabolic rate. Proc Nutr Soc. 2003;62:621–634.
10. Westerterp KR, Meijer GA, Schoffelen P, Janssen EM. Body mass, body composition and sleeping metabolic rate before, during and after aerobic training. Eur J Appl Physiol Occup Physiol. 1994;69:203–208.
11. Westerterp KR. Pattern and intensity of physical activity. Nature. 2001;410:539.