Nov 29, 2016 05:09PM
Work first, exercise later
A new study by the University of Alabama at Birmingham says exercise may be the best way to curb an appetite after a long day at the office. Researchers found those who exercised after doing mental work or tasks ate fewer calories than those who remained sedentary.
UAB researchers asked 38 students to complete a graduate level exam. Participants were put into two groups, one given 15 minutes of rest afterward, the other given 15 minutes of high-intensity interval training on a treadmill. Each group was then offered an all-you-can eat lunch of pizza. Those who rested for 15 minutes ate an average of 100 more calories than those who exercised. Researchers said the study confirmed that working the brain expends energy and causes feelings of hunger. But because the lactate levels increase in those who exercise, it may "replenish the brain's energy needs," researchers believe.
"One possible explanation is exercise's effect on hunger and satiety hormones may decrease energy intake after activities that stimulate one's appetite," said William Neumeier, Ph.D., the study's lead author.
Neumeier, a Post Doctoral Fellow at the UAB Nutrition Obesity Research Center, said they undertook the study to prove the hypothesis that exercise could partly replenish the brain's desire for additional energy. While reading only burns about 1.5 calories per minute, increased mental exhaustion and stress after difficult tasks could lead one to overeat. Studies have already indicated that desk jobs can increase obesity through their sedentary nature. A 2014 study in American Journal of Preventive Medicine found that engineers, office administrators and social-service workers had unusually high obesity rates after adjusting for demographics and other factors. Neumeier says it's an increasing problem as U.S. labor trends over the past few decades have shifted to more white-collar employment.
"Mentally demanding tasks are something that many of us encounter every day and they may contribute to increased body weight over the past 50-60 years," Neumeier says.
Since exercise burns calories and often requires the person to replenish more calories by eating more, it doesn't necessarily increase appetite. Neumeier says many people don't fully compensate for the energy expanded during exercise, thus producing a caloric deficit. "The person may still consume more foods but hasn't fully compensated for the energy expenditure of the exercise. Thus, exercise may 'reduce appetite,'" Neumeier says.
There is still debate among medical and health professionals about the most optimal time to exercise. A 2012 study at BYU measured how women responded to food after exercising first thing in the morning. It found that those who had a brisk 45-minute walk were less distracted by crave-inducing food and also increased their physical activity more the rest of the day. Yet a 2010 study published in the journal of Chronobiology International found that peak exercise time is between 2 and 6 p.m. due to increase enzyme activity and muscular function due to body and rising environmental temperature.
The American Heart Association says at its website that when to exercise is less important than simply doing it when it's convenient and establishing a routine.
"The best time of the day is when you will do it most consistently, because the benefits of physical activity are tightly linked to the amount you do on a consistent basis," says Russell Pate, Ph.D., professor of exercise science in the Arnold School of Public Health at the University of South Carolina, Columbia.
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