“This research has practical implications if we want to avoid overindulging in gratitude,” says Jonathan Z. Long, a professor of pathology at Stanford University School of Medicine, who suggests “running the turkey trot” or otherwise engaging ourselves in fast, sweaty movements. Clinical Medicine Studying the Cellular Effects of Exercise and Starvation.
The amount of exercise affects appetite.
The effects of exercise on appetite are powerful but rare. Exercise requires energy. Appetite, driving by eating, helps to provide. So it makes sense that exercise makes us hungry. And, usually, it does. Many StudiesPeople who do moderate exercise, such as walking, later end up lethargic and ready to touch.
But not when they push themselves. Most people “don’t feel hungry after a hard workout,” says Long.
But why and how? Long, himself an avid runner as well as a scientist, wondered if molecules circulating in our blood after exercise might be involved. These molecules migrate to the brain or other organs and bypass processes that suppress or suppress hunger.
To find out, he and more than two dozen colleagues looked closely at mice before and after they ran to exhaustion on a tiny treadmill. b ResearchThe scientists used a process called mass spectrometry to chart changes in the levels of molecules involved in metabolism in the animals’ blood after exercise.
They got a lot. But after the animals ran, one in particular was shot and shot. This is an obscure molecule that scientists have not previously named or documented. The chemical makeup of the molecule, which the researchers are currently working on, is a mixture of lactate, a compound produced by cells during intense exercise, and the amino acid phenylalanine. The scientists named it lac-phe, and from their data they found that the more lactate the mice pumped out during exercise—that is, the harder they ran—the more lac-phe was converted into their blood.
A molecule that suppresses appetite after exercise
Next, they set out to see if lac-phe affected hunger, injecting it into inactive mice that were enjoying a snack. The animals immediately “cut their food intake in half over a 12-hour period,” Long said. Similarly, when lac-phe-deficient mice were bred and made to race harder on a treadmill, the animals became more self-replete compared to mouse runners with higher levels of lac-phe. Without the molecule, intense exercise stimulated appetite.
Finally, they found an increase in lact-phe in people’s blood if they cycled slowly, lifted weights or during high-intensity intervals. “We found that spring produced the highest lac-phene levels, followed by weight training and then cardio,” Long said.
In other words, vigorous exercise produced more appetite-suppressing molecules than light exercise did.
The study caused a scientific stir and prompted some commentators to speculate. other Papers That lac-phe could eventually be purified for medicinal use, to dull people’s appetites, without the need for strenuous exercise first.
Exercise does not help you ‘get’ food.
But most exercise scientists think that exercise’s effect on hunger is greater than the function of any single molecule. Studies show that exercise has a profound effect on various hormones. In general, moderate or light activity increases levels of the hormone that makes you want to eat more, specifically acetylated ghrelin (or simply ghrelin).
“Exercise-induced suppression of ghrelin is consistent across our studies,” says Tom Hazell, a professor of kinesiology at Wilfred Laurier University in Waterloo, Ontario, who has extensively studied exercise and eating behavior.
as if A new study In a study published last May by his lab, nine middle-aged participants showed meaningfully reduced ghrelin levels after engaging in repetitive, intense, one-minute or 15-second intervals of exercise. The results echo his team’s earlier ones. job, It also found that ghrelin drops shortly after intense exercise and remains low for about two hours.
Interestingly, in some of his group’s studies, human ghrelin levels, in contrast, tracked blood lactate levels in the lac-phe study. As their lactate levels rise, indicating they are working harder, ghrelin drops further, which can reduce hunger.
Many other different body processes and parts also play a role in exercise and appetite, including our brain. In some close animals StudiesFor example, intense exercise temporarily changes the firing of hunger-specific neurons, increasing activity in people that appear to reduce appetite and increasing it in others that control hunger. This process has not yet been demonstrated in humans.
It also remains a mystery how all these systems and processes interact and differ between sexes, between women. Different stages of menstruationBetween the old and the young, heavy and lean, or mice and us.
Basically, “thinking of exercise as a way to ‘get food’ is a bad idea,” says Glen Gesser, a professor of exercise physiology at Arizona State University in Phoenix who studies exercise and weight management.
For one thing, exercise burns fewer calories. “In one study,” he said, “we had subjects eat two donuts, for a total of 520 calories. It took less than five minutes to eat the donuts, but close to an hour or more to burn them off” with exercise.
After all, exercise has its own incalculable rewards, like a Thanksgiving buffet, and tooling one over the other can dull the joys of both.
Still, if you want to slip in a Turkey Day workout and eat less, “high-intensity exercise is the way to go, as is high-intensity interval training,” says Hazell.
Have a fitness question? email YourMove@washpost.com And we will answer your question in the next column.