The study, conducted by Paul Williams of the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), followed 6,119 men and 2,221 women who maintained their weekly running mileage (to within three miles per week) over a seven-year period. On average, the men and women who ran over 30 miles per week gained half the weight of those who ran less than 15 miles per week.
"To my knowledge, this is the only study of its type," says Williams, a staff scientist in Berkeley Lab's Life Sciences Division. "Other studies have tracked exercise over time, but the majority of people will have changed their exercise habits considerably."
The research is the latest report from the National Runners' Health Study, a 20-year research initiative started by Williams that includes more than 120,000 runners. It appears in the May 3 issue of the journal Medicine and Science in Sports and Exercise.
Guys, even if you run more than 30 miles a week (not gonna do it) you'll still gain more than half a pound annually. Over 40 years that adds up to 32 pounds. Ugh.
Specifically, between the time subjects entered the study and when they were re-contacted seven years later, 25-to-34-year-old men gained 1.4 pounds annually if they ran less than 15 miles per week. In addition, male runners gained 0.8 pounds annually if they ran between 15 and 30 miles per week, and 0.6 pounds annually if they ran more than 30 miles per week.
Is there a level of exercise at which people do not gain weight as they age? If so, what is that level?
Women who ran more than 30 miles a week gained more weight than men who did.
This trend is mirrored in women. Women between the ages of 18 and 25 gained about two pounds annually if they ran less than 15 miles per week, 1.4 pounds annually if they ran 15 to 30 miles per week, and slightly more than three-quarters of a pound annually if they ran more than 30 miles per week. Other benefits to running more miles each week included fewer inches gained around the waist in both men and women, and fewer added inches to the hips in women.
A chart on calories burned in various forms of exercise (also see here and here) suggests these joggers are burning up perhaps 100-120 calories per mile (the possible range is larger depending on weight and other factors). So the 30 mile per week runners might be burning 3000 calories per week or 150,000 calories per year. They burn about 150,000 calories to keep off maybe a pound per year? Maybe only 1% or 2% of the additional calories burned translate into a reduction in fat accumulation. Note I'm doing really rough calculations ignoring body size and other factors. We'd need to see numbers on weight gain of non-runners to make an exact calculation. But the amount of calories one needs to burn is pretty large if the goal is weight control.
The calories burnt running are only part of the story though. The runners probably have more muscle than non-exercisers. So they burn more calories when they are sitting still (muscles use energy even when not doing work). The exercise must increase their appetites almost as much as it increases their calorie burning.
Do the Amish farmers gain weight as they grow old? Or do any other higher exercise groups keep off the weight as they grow older?
Update: Is there some way using less exercise to shift the body into a state where it is less likely to accumulate fat? Maybe. Short high intensity interval training increases the amount of fat burnt in all exercise.
Researchers at McMaster University in Hamilton, Ontario, had the exercisers sprint for 30 seconds, then either stop or pedal gently for four minutes.
Such a stark improvement in endurance after 15 minutes of intense cycling spread over two weeks was all the more surprising because the volunteers were already reasonably fit. They jogged, biked or did aerobic exercise two to three times a week.
Doing bursts of hard exercise not only improves cardiovascular fitness but also the bodyís ability to burn fat, even during low- or moderate-intensity workouts, according to a study published this month, also in the Journal of Applied Physiology. Eight women in their early 20s cycled for 10 sets of four minutes of hard riding, followed by two minutes of rest. Over two weeks, they completed seven interval workouts.
After interval training, the amount of fat burned in an hour of continuous moderate cycling increased by 36 percent, said Jason L. Talanian, the lead author of the study and an exercise scientist at the University of Guelph in Ontario. Cardiovascular fitness ó the ability of the heart and lungs to supply oxygen to working muscles ó improved by 13 percent.
But this research is too small in scale and in time interval to tell us anything about the long term effects of high intensity exercise for short periods of time. Will such a pattern of exercise reduce weight gain with age?
To compare soy peptides with leptin, de Mejiaís graduate student Nerissa Vaughn, with the help of associate professor Lee Beverly, implanted cannulas in the brains of lab rats; they then injected leptin as a positive control. When the scientists could see their model was working, they injected two formulations of hydrolyzed soy protein and soy peptides so the scientists could monitor the effects of each on food intake and weight loss.
Injections were given three times a week for two weeks; during that time, the animals had unlimited access to food and water. Food intake was measured 3, 6, 12, 24, and 48 hours after injection, and the rats were weighed 24 and 48 hours after injection. All rats received the same amount of exercise, and all rats lost weight.
But, after the third injection, de Mejia and Vaughn noticed a significant weight loss in the group of animals that had received one of the soy hydrolysates, even though the animals hadnít changed their eating habits. In this instance, soy protein appeared to have caused weight loss not by reducing food intake but by altering the ratsí metabolism.
The experiment not only showed that soy peptides could interact with receptors in the brain, it also demonstrated that eating less isnít always the reason for weight loss, the researcher said.
While these scientists used injection the press release claims that other research has shown that increased soy consumption is correlated with reduced weight. I've not read that claim before. Does that ring a bell with anyone else? If you are familiar with that research please post a comment.
Update III: A friend who suffers from arthritis says that the long term costs of joint wear from running have to be considered when deciding how to keep off the weight. Many of those who already have bad knees, hips and backs can't go running 30 miles a week without suffering intense pain. But what about the younger ones with still good joints? Do they put themselves at greater risk of knee and hip arthritis if they run 30 miles a week?
Stem cell therapies to replenish aging joint stem cells will some day allow people to avoid osteoarthritis and other joint problems that come with age. If we already had the needed cell therapies then the long term advantage of running would be clearer cut. But in the mean time aerobic exercise in ways that reduce joint impact (e.g. swimming and perhaps exercise cycles?) might make more sense as a way to get the exercise with less wear and tear on the joints.
|Share |||Randall Parker, 2007 May 05 06:17 PM Aging Exercise Studies|