Obesity afflicts many people, with a study published earlier this year in the medical journal The Lancet showing that more than 1 billion people — or roughly one out of eight people alive today — struggles with the condition. Along with the social stigma associated with being “fat,” obesity comes with a heightened risk for a wide range of health issues including heart attacks, diabetes, strokes, fatty liver diseases, metabolic disorders, sleep apnea and various types of cancer.
Conventional wisdom dictates that, for these people to lose weight, they need to eat better and exercise more. Yet a recent study in the journal Medicine & Science in Sports & Exercise found that at least part of this equation doesn't help as much as conventional wisdom would suggest. In fact, this research found people who vigorously exercise usually experience a drop in body temperature and non-exercise physical activity (NEPA). As a result, they wind up gaining weight.
“Exercise has many beneficial effects on the body and mind, but weight loss is often less effective than expected,” study co-author Dr. Takashi Matsui, who teaches at the University of Tsukuba’s Institute of Health and Sport Sciences, told Salon. “This is assumed to be due to a decrease in post-exercise physical activity and heat production, which may be maintained or reduced by total daily energy expenditure. However, it was not known under what conditions and through what physiological mechanisms the post-exercise decrease in physical activity occurs.”
In their new study, Matsui and his team examined the effects of post-exercise physical activity to determine whether exercise leads to weight loss. Importantly, they were able to control for factors like genetics and environmental and social factors.
“The results revealed for the first time that a single bout of not-so-moderate, strenuous exercise leads to a decrease in physical activity and body temperature, which in turn leads to an increase in body weight,” Matsui said. “We also learned for the first time that part of the mechanism is a disruption of the circadian rhythm of corticosterone, the stress hormone that produces our well-rounded lives.”
Unfortunately for those who try to lose weight, Matsui observed that they often strenuously work out in a desire "reap the benefits of exercise" and "lose weight through exercise." Because of these misleading cultural drives, “sudden intense exercise may have the opposite effect of people's desire to benefit from exercise and to exercise and lose weight. Additionally, although different from this study, strenuous exercise is also known to carry risks of injury and weakening of the immune system.”
Dr. Nicole Avena, an assistant professor of neuroscience at Mount Sinai Medical School and visiting professor of health psychology at Princeton University, was not involved in the study. Speaking with Salon, Avena praised the researcher’s conclusions, although she emphasized that exercise is still healthy and should therefore be encouraged.
“Intentional exercise is great for our cardiovascular, muscular and hormonal health overall,” Avena said. “Currently, the recommendation stands at 30 minutes of moderate physical activity per day to see benefits like these. With regular exercise you can expect less mood swings, more energy and better sleep — which may not be known to some!”
This does not mean that Avena does not see downsides to exercising, at least when it is done excessively.
“Overexercising can be problematic — and cause health issues including malnutrition, fatigue and injury,” Avena said. “Sticking with moderate intensity should not cause any of the unwanted side effects when paired with proper nutrition.”
Matsui also presented a balanced view of exercise. He described its "many beneficial effects on the body and mind,” urging readers to instead do it in moderation so that they do not burn out.
“The ‘tiredness’ and ‘hopelessness’ that accompany these phenomena may prevent us from doing the really important"moderate exercise habitually,” Matsui said. “This can be understood as a defensive reaction as animals.”
If a human in the wild was attacked and had to fight to escape with their life, he or she would then respond like most other animals — hunkering down and resting so they can recover.
"It is easy to imagine that these behaviors and physiological responses helped preserve the individual and the species, i.e., the baton of life,” Matsui said. “However, this response can be counterproductive in modern society. What we have learned in this study is that it is not caused solely by a psychological’"tiredness,’ but is accompanied by a disturbance in a distinct physiological response: the circadian rhythm of the stress response.”
As a result, Matsui suggests that people struggling with obesity focus not on losing weight, but on developing a regimen of regular moderate amounts of exercise.
“Make exercise a habit by performing moderate exercise that you want to continue the next day,” Matsui said. “What is really important, of course, is consistency.”
For her part, Avena hopes that studies like this one will get people to start thinking of exercise not in terms of beating obesity, which often isn’t possible, but rather simply so they can lead happier and healthier lives.
“I think it's important to emphasize the health benefits of exercise outside of weight,” Avena said. “Exercise is good for our mental, physical and emotional wellbeing!”
