Conventional wisdom has it that the more energy we expend, the hungrier we will be. That same wisdom also suggests that the less active we are, the less we will want to eat.
A new study upends these popular theories and finds that being active may not only blunt the appetite, but may suppress it. It also finds that the less active we are, the hungrier we perceive ourselves to be.
The results are contained in the first study yet to examine whether too much sitting alters our perception of our hunger. The team of Kirsten Granados, Brooke Stephens, Steven Malin and Barry Braun, Department of Kinesiology, University of Massachusetts Amherst; and Marc Hamilton and Theodore Zderic, Department of Biomedical Sciences, University of Missouri, Columbia conducted the study, entitled "Effects of Inactivity and Energy Status on Appetite Regulation in Men and Women."
Six young, lean and fit men and women who were recruited for the study were first kept within a strict energy balance (amount of calories expended matched to calories consumed) for several days. They then were enrolled in three consecutive one-day "conditions" that occurred one week apart in random order:
• Condition 1: In this condition, the volunteers spent 12 hours being physically active but not doing anything that is classified as "exercise." They performed a series of highly scripted activities, which included walking, sorting papers, picking up books and folding laundry. The participants could not sit for more than 10 minutes each hour for the entire 12-hour period. They also consumed the number of calories that was roughly equivalent to the amount of energy they had expended.
• Condition 2: In this condition, the volunteers were highly inactive. They watched videos, worked on computers, and were allowed to move about only by being pushed in wheelchairs by the investigators. The condition lasted for 12 hours, and the caloric intake matched that of the prior condition, creating a low activity/high calorie condition.
• Condition 3: In the third condition, the volunteers again were very inactive, and watched videos, sat at computers and were moved around by wheelchair for 12 hours. However, unlike the previous condition, the calories the participants received were substantially reduced to match the amount of energy they had expended.
Appetite questionnaires were administered before and for six hours after consuming a standard meal and in the morning of the following day. The researchers also measured three hormones involved in appetite regulation: acylated ghrelin, leptin and insulin.
The researchers found:
Participants under condition 3 and condition 2 felt hungrier (+12%, +17%), had a greater desire to eat (+14%, 18%), and reported they could consume more food (+10%, +8%) compared to condition 1.
Participants under condition 3 and condition 2 reported feeling less satisfied (-16%, -12%) than during condition 1. The results suggest inactivity may increase the perception of hunger and decrease the perception of fullness (satiety).
Although the results are still preliminary, the data suggest that low-intensity activities such as walking seem to have a blunting effect on appetite.
"In addition to reducing energy output, sitting for long periods may increase the perception of hunger. If you are sitting on the couch or at your desk, not only are you not burning calories, it may cause you to want more of them," Braun said.