Tagged Fitness

Out of Shape at 18, at Risk for Future Diabetes

Photo

Being out of shape at age 18 may increase your risk for eventually developing Type 2 diabetes, regardless of your weight and family history, a new study says.

The study looked at data from more than 1.5 million Swedish men, using tests of muscle strength and aerobic capacity when they were conscripted for military service at age 18, between 1969 and 1997. Their muscle strength had been measured with hand grip and other tests, and their aerobic capacity calculated as they exercised on a stationary bicycle.

With this data in hand, researchers checked the men’s medical records from 1987 to 2012. They found 34,008 cases of Type 2 diabetes over an average 26 years of follow-up. The study is in the Annals of Internal Medicine.

Both low aerobic capacity and low muscle strength at 18 were associated with a higher risk for Type 2 diabetes; poor aerobic capacity was a slightly stronger risk factor. Having both weak muscles and low aerobic capacity more than tripled the risk for future diabetes. The effect was independent of other risk factors — body mass index, family history of diabetes, education and socioeconomic status.

“Early life interventions are really important,” said the lead author, Dr. Casey Crump, a professor of family medicine at the Icahn School of Medicine at Mount Sinai in New York. “Prevention of Type 2 diabetes should begin early in life, and should include both aerobic fitness and muscular strength. This is important regardless of people’s weight.”

For Serious Training, Hold the Carbs at Dinnertime

Photo

Triathletes plunged into the Hudson River for the 12th annual N.Y.C. Triathlon held in 2012.

Triathletes plunged into the Hudson River for the 12th annual N.Y.C. Triathlon held in 2012.Credit Christopher Gregory for The New York Times

Strategically skipping bread, pasta and other carbohydrates at dinner might improve subsequent athletic performance, provided those low-carb meals are combined with the right types of workouts, according to a new sports nutrition study. Its findings undercut some entrenched ideas about how athletes should eat in preparation for spring marathons and other endurance races.

As those of us who are athletes or spend time around them know, diets are a topic of consuming interest for the group, since an athlete’s diet affects how well he or she can train, recover, progress, chisel a physique and compete.

But the ideal sports diet remains elusive. Many dietitians and coaches advocate for heaps of carbohydrates at the training table. Carbohydrates, which break down during digestion into sugar, are the body’s first choice as fuel during exercise. But the body’s reservoir of stored carbohydrates is small, and even if athletes supplement their supply during exercise with sugary drinks or food, prolonged or intense exertion generally incinerates much of the body’s available carbohydrates.

Consequently, some experts suggest that athletic success may depend in part on making the body better able to use fat as a fuel. Even the leanest athlete’s body is girded with the stuff, theoretically providing enough energy for even the longest, hardest workouts. Low-carbohydrate diets will force the body to turn to fat. But working muscles must become used to burning fat, a process that can make exercising on a low-carb diet difficult in the short term. Indeed, athletes on extremely low-carbohydrate diets tend to struggle to finish hard workouts.

So researchers at the French National Institute of Sport, Expertise and Performance in Paris and other institutions began to wonder about the possibilities of modified forms of low-carb diets, and specifically about what they and other scientists call “sleeping low.”

With a “sleep-low” sports diet, an athlete skips carbohydrates at dinner. In the morning, his or her body should have low reserves of the macronutrient, and any ensuing workouts would force the body to turn to fat, its most abundant fuel. In past studies of the technique, however, it has produced mixed results in terms of whether it improves competitive performance.

The authors of the new study, which was published in January in Medicine & Science in Sports & Exercise, suspected that the sleep-low diet needed to be integrated into a broader training plan in order to show desirable results.

To test that possibility, they recruited 21 experienced, competitive triathletes who bravely agreed to have their diets manipulated. The scientists ran their volunteers through a simulated triathlon and other tests of their current fitness and pace.

Half of the athletes were then randomly assigned to eat a standard sports diet, with large helpings of carbohydrates at every meal and after workouts.

The others were put on a sleep-low regimen. With this program, the athletes consumed the same amount of carbohydrates over the course of the day as the other group, but in a different sequence. Virtually all of their carbohydrates were consumed at breakfast and lunch, with none at dinner.

At the same time, all of the athletes also began a new training program. In the afternoon, both groups completed a draining, intense interval-training session, designed to increase fitness and deplete the body’s carbohydrate stores. The members of the control group then replenished their carbohydrates at dinner; the sleep-low group did not.

Next morning, before breakfast, the volunteers pedaled for an hour at a moderate pace on stationary bicycles. By this time, the sleep-low group was running on carbohydrate fumes and body fat.

Afterward, all of the athletes sat down to large, carb-rich breakfasts and lunches, meaning that both groups were flush with carbohydrates for the afternoon interval training.

This program continued for four days per week for three weeks. (On the remaining days, the athletes ran, cycled or swam at an easy pace and ate as they chose.)

After three weeks, the athletes in the sleep-low group were grumbling about evening hunger.

But when the researchers now repeated the simulated triathlon, those athletes in the sleep-low group showed notable improvement. Their times on the 10-kilometer running leg at the end of the race were faster by about 75 seconds, or 3 percent, than at the start of the study. The control group had not improved.

The sleep-low volunteers also had lost body fat, while the other athletes had not.

These findings suggest, said Laurie-Anne Marquet, a graduate student at the French National Institute of Sport who led the study, that exercising strenuously in the afternoon, depriving yourself of carbohydrates afterward, training gently the next morning and then swallowing a mound of pancakes might be a useful way to improve endurance and performance. The regimen seemed to have increased the athletes’ ability to access fat as muscle fuel, she said, allowing them to exercise harder during the workouts than the control group and gain additional fitness and speed.

Such a rigorous routine is not for everyone, of course. Those of us not training for a marathon, triathlon or similar event probably would not enjoy or benefit from sleeping low. Even serious athletes should thread the approach into their training cautiously, Ms. Marquet said, beginning a few weeks before a race and easing off in the days just before the event, when they should down carbohydrates at will.

Encouragingly for those tempted by the diet, though, “most of the athletes” in the study, Ms. Marquet said, “have now integrated this strategy into their training.”

Related:

For more fitness, food and wellness news, follow us on Facebook and Twitter, or sign up for our newsletter.

Running for the Wrong Reasons

Excerpted from Jen A. Miller’s new book, “Running: a Love Story: 10 Years, 5 Marathons, and 1 Life-Changing Sport.”

Photo

Credit

When I was 13 years old, Avalon, the shore town I’ve gone to every summer of my life, started a dredging project to widen the beaches. They took sand from the ocean floor and transferred it onto land. It worked, but it also kicked up seaweed. A lot of seaweed. I was determined to swim anyway, but it clung everywhere, catching in the crooks of my elbows, my knees, my hair. I tried to float over it on a boogie board, but it hooked onto the strap that connected the board to my wrist and weighed me down.

That’s what dating Steve was like. In David Carr’s memoir “The Night of the Gun,” he called this kind of relationship a “minuet of misery.” As Stephen dropped deeper into alcoholism, creating and breaking his own rules (it’s not a problem if I only drink on weekends, it’s not a problem if it doesn’t affect my work, it’s not a problem if I’m a little hungover at work), and as his calls became later, more frantic, and more frequent, he pulled me down too.

That first 5K in Medford came eight months into this mess. I had managed to eat enough to maintain that training, skating on the edge of eating too little to be too small, but I plunged over the edge soon after. I kept running after that 5K, but it was for him. I wanted to be as small as possible, and I saw running as a path toward that goal. I had a strength training routine down. I was in the weight room four days a week, lifting 20, 25, 30, 40, 50 pounds at low reps just like Steve said, but I still didn’t look like Jessica Alba from Sin City, who he had on a poster in his basement. “You can look like that,” he said one night as we played pool, Jessica staring down at me as I tried to sink the eight ball. (I didn’t. I scratched.)

If I do that, if I can look like that, I told myself, it’ll finally flip that switch in him, turn a relationship held together by spider webs into something solid and real. Running burned more calories an hour than any other cardio I could do in the gym. Running needed to be part of my life then so I could show Steve what I was willing to do for him. I didn’t enjoy the miles like I used to. Those days of bounding around Knight Park being serenaded by birds and kids and Little League games were gone. Now I was trapped in the run, like I was trapped with him, trying to use one as the means to an end with the other.

Photo

Credit Marc Steiner

The more I drank, the more I smoked, the less I ate. I vowed to do better with my no-carb, no-fat diet: No more slip-ups. No more carbs at all. And if I did make a mistake — a plate of cheese-covered nachos when out with friends, Saturday sandwiches with Mom — I puked it back up. It wasn’t that different from throwing up after a long night of drinking, right? So what was wrong with getting rid of too much food?

On one cool morning six months before the end, when we hadn’t called or texted or emailed in nearly a week — a new record! — I went for a run. It was a gorgeous, clear day, the first one after the summer heat had finally broken. The world felt wiped clean. Maybe, I thought, that day could be a new start for me too.

I ran straight for Knight Park on my usual 3-mile route. I started feeling that strength again that I had found in training for the 5K, in moving my body forward, one step at a time. But one minute I was looking at the war memorial on the corner of the park and the next I was staring up at the concerned face of a mom and her 2-year-old.

“You O.K.?” she asked as her toddler yelled “Boo-boo! Booboo!” over and over again. “You just went down.” I was 115 pounds, a weight I hadn’t been since middle school.

“Oh, I’m O.K. I didn’t drink any water today,” I lied, and let her help me stand up. My vision started to fade again, so I held on to her shoulder.

“Let me drive you home,” she said.

“No, I’m O.K.,” I said, first to her, then to her son, whose eyes were now wide with terror. I played peek a boo with him until he smiled and offered me his binkie. My vision had stopped graying by then, and I shuffled home.

Excerpted from “Running: A Love Story” by Jen Miller. Available from Seal Press, a member of The Perseus Books Group. Copyright © 2016.

Learning a New Sport May Be Good for the Brain

Photo

Gretchen Reynolds, Phys Ed columnist, tries snowboarding for the first time.

Gretchen Reynolds, Phys Ed columnist, tries snowboarding for the first time.Credit Lynn Tran

Learning in midlife to juggle, swim, ride a bicycle or, in my case, snowboard could change and strengthen the brain in ways that practicing other familiar pursuits such as crossword puzzles or marathon training will not, according to an accumulating body of research about the unique impacts of motor learning on the brain.

When most of us consider learning and intelligence, we think of activities such as adding numbers, remembering names, writing poetry, learning a new language.

Such complex thinking generally is classified as “higher-order” cognition and results in activity within certain portions of the brain and promotes plasticity, or physical changes, in those areas. There is strong evidence that learning a second language as an adult, for instance, results in increased white matter in the parts of the brain known to be involved in language processing.

Regular exercise likewise changes the brain, as I frequently have written, with studies in animals showing that running and other types of physical activities increase the number of new brain cells created in parts of the brain that are integral to memory and thinking.

But the impacts of learning on one of the most primal portions of the brain have been surprisingly underappreciated, both scientifically and outside the lab. Most of us pay little attention to our motor cortex, which controls how well we can move.

“We have a tendency to admire motor skills,” said Dr. John Krakauer, a professor of neurology and director of the Center for the Study of Motor Learning and Brain Repair at Johns Hopkins University in Baltimore. We like watching athletes in action, he said. But most of us make little effort to hone our motor skills in adulthood, and very few of us try to expand them by, for instance, learning a new sport.

We could be short-changing our brains.

Past neurological studies in people have shown that learning a new physical skill in adulthood, such as juggling, leads to increases in the volume of gray matter in parts of the brain related to movement control.

Even more compelling, a 2014 study with mice found that when the mice were introduced to a complicated type of running wheel, in which the rungs were irregularly spaced so that the animals had to learn a new, stutter-step type of running, their brains changed significantly. Learning to use these new wheels led to increased myelination of neurons in the animals’ motor cortexes. Myelination is the process by which parts of a brain cell are insulated, so that the messages between neurons can proceed more quickly and smoothly.

Scientists once believed that myelination in the brain occurs almost exclusively during infancy and childhood and then slows or halts altogether.

But the animals running on the oddball wheels showed notable increases in the myelination of the neurons in their motor cortex even though they were adults.

At the same time, other animals that simply ran on normal wheels for the same period of time showed no increase in myelination afterward.

In other words, learning the new skill had changed the inner workings of the adult animals’ motor cortexes; practicing a well-mastered one had not.

“We don’t know” whether comparable changes occur within the brains of grown people who take up a new sport or physical skill, Dr. Krakauer said. But it seems likely, he said. “Motor skills are as cognitively challenging” in their way as traditional brainteasers such as crossword puzzles or brain-training games, he said. So adding a new sport to your repertory should have salutary effects on your brain, and also, unlike computer-based games, provide all the physical benefits of exercise.

These considerations cheered me a few weeks ago when I took to the slopes of my local mountain for a weekend-long crash course in snowboarding. (Crashing, regrettably, is inevitable while learning to shred.) I had wondered if I might be too advanced in years and hardened in the habits of skiing to learn to ride. But the experience was in fact exhilarating and glorious. Learning a new sport or skill when you are old enough to be a parent to your instructor is psychologically uplifting, as well as beneficial for the body and brain. It reminds you that your body can still respond, that it can still yearn for movement and speed.

By the end of the second day, I attempted my first moguls on a snowboard and completed precisely one turn before auguring hindside into the slope and slipping and picking my way down the rest of the run. But one mogul turn was 100 percent more than I had managed before. I now aim to return to the mountain and double that number to two turns, which is how we learn and progress and, with luck, change our minds — both literally and about our limits.

Related:

For more fitness, food and wellness news, follow us on Facebook and Twitter, or sign up for our newsletter.

Ask Well: Why Daily Weight Lifting Can Be Dangerous

Photo

David Abusheik, 18, lifts weights for two hours a day, six days a week at Dolphin Fitness in Fort Hamilton, Brooklyn.

David Abusheik, 18, lifts weights for two hours a day, six days a week at Dolphin Fitness in Fort Hamilton, Brooklyn.Credit Béatrice de Géa for The New York Times

Do you have a health question? Submit your question to Ask Well.

Related:

For more fitness, food and wellness news, follow us on Facebook and Twitter, or sign up for our newsletter.

Which Type of Exercise Is Best for the Brain?

Photo

Credit Getty Images

Some forms of exercise may be much more effective than others at bulking up the brain, according to a remarkable new study in rats. For the first time, scientists compared head-to-head the neurological impacts of different types of exercise: running, weight training and high-intensity interval training. The surprising results suggest that going hard may not be the best option for long-term brain health.

As I have often written, exercise changes the structure and function of the brain. Studies in animals and people have shown that physical activity generally increases brain volume and can reduce the number and size of age-related holes in the brain’s white and gray matter.

Exercise also, and perhaps most resonantly, augments adult neurogenesis, which is the creation of new brain cells in an already mature brain. In studies with animals, exercise, in the form of running wheels or treadmills, has been found to double or even triple the number of new neurons that appear afterward in the animals’ hippocampus, a key area of the brain for learning and memory, compared to the brains of animals that remain sedentary. Scientists believe that exercise has similar impacts on the human hippocampus.

These past studies of exercise and neurogenesis understandably have focused on distance running. Lab rodents know how to run. But whether other forms of exercise likewise prompt increases in neurogenesis has been unknown and is an issue of increasing interest, given the growing popularity of workouts such as weight training and high-intensity intervals.

So for the new study, which was published this month in the Journal of Physiology, researchers at the University of Jyvaskyla in Finland and other institutions gathered a large group of adult male rats. The researchers injected the rats with a substance that marks new brain cells and then set groups of them to an array of different workouts, with one group remaining sedentary to serve as controls.

Some of the animals were given running wheels in their cages, allowing them to run at will. Most jogged moderately every day for several miles, although individual mileage varied.

Others began resistance training, which for rats involves climbing a wall with tiny weights attached to their tails.

Still others took up the rodent equivalent of high-intensity interval training. For this regimen, the animals were placed on little treadmills and required to sprint at a very rapid and strenuous pace for three minutes, followed by two minutes of slow skittering, with the entire sequence repeated twice more, for a total of 15 minutes of running.

These routines continued for seven weeks, after which the researchers microscopically examined brain tissue from the hippocampus of each animal.

They found very different levels of neurogenesis, depending on how each animal had exercised.

Those rats that had jogged on wheels showed robust levels of neurogenesis. Their hippocampal tissue teemed with new neurons, far more than in the brains of the sedentary animals. The greater the distance that a runner had covered during the experiment, the more new cells its brain now contained.

There were far fewer new neurons in the brains of the animals that had completed high-intensity interval training. They showed somewhat higher amounts than in the sedentary animals but far less than in the distance runners.

And the weight-training rats, although they were much stronger at the end of the experiment than they had been at the start, showed no discernible augmentation of neurogenesis. Their hippocampal tissue looked just like that of the animals that had not exercised at all.

Obviously, rats are not people. But the implications of these findings are provocative. They suggest, said Miriam Nokia, a research fellow at the University of Jyvaskyla who led the study, that “sustained aerobic exercise might be most beneficial for brain health also in humans.”

Just why distance running was so much more potent at promoting neurogenesis than the other workouts is not clear, although Dr. Nokia and her colleagues speculate that distance running stimulates the release of a particular substance in the brain known as brain-derived neurotrophic factor that is known to regulate neurogenesis. The more miles an animal runs, the more B.D.N.F. it produces.

Weight training, on the other hand, while extremely beneficial for muscular health, has previously been shown to have little effect on the body’s levels of B.D.N.F., Dr. Nokia said, which could explain why it did not contribute to increased neurogenesis in this study.

As for high-intensity interval training, its potential brain benefits may be undercut by its very intensity, Dr. Nokia said. It is, by intent, much more physiologically draining and stressful than moderate running, and “stress tends to decrease adult hippocampal neurogenesis,” she said.

These results do not mean, however, that only running and similar moderate endurance workouts strengthen the brain, Dr. Nokia said. Those activities do seem to prompt the most neurogenesis in the hippocampus. But weight training and high-intensity intervals probably lead to different types of changes elsewhere in the brain. They might, for instance, encourage the creation of additional blood vessels or new connections between brain cells or between different parts of the brain.

So if you currently weight train or exclusively work out with intense intervals, continue. But perhaps also thread in an occasional run or bike ride for the sake of your hippocampal health.

Related:

For more fitness, food and wellness news, follow us on Facebook and Twitter, or sign up for our newsletter.

Getting People to Exercise Requires the Right Incentive

Photo

Credit Karsten Moran for The New York Times

People will exercise more if you give them money — but only if they are paid in the right way.

For a 13-week study, researchers randomly assigned 281 people to one of four groups. The goal for each person was to achieve 7,000 steps a day, recorded on a smartphone accelerometer.

Those in the first group got $1.40 for each day they reached the goal. In the second group, the reward for success was entry into a lottery with a possible payoff of $100. Those in the third were given $42 the first day of every month, deposited in an online account, and had $1.40 automatically deducted each day they failed to achieve 7,000 steps. A control group received only daily feedback about their performance. The study is in Annals of Internal Medicine.

The control group achieved their goal 30 percent of the time, and the lottery and paid-every-day groups performed statistically no better, at 35 percent. But the group paid upfront, risking a loss every day, succeeded 45 percent of the time.

“There’s a presumption that tracking your activity will help you change your behavior,” said the lead author, Dr. Mitesh S. Patel, an assistant professor at the University of Pennsylvania. “But it typically doesn’t work unless it’s combined with behavior change strategies. Our study shows that the design of the incentive is critical to its success.”

Why We Get Running Injuries (and How to Prevent Them)

Photo

Credit Getty Images

Warm weather is on its way across the country — really, it is, I promise— and so are spring marathons, meaning that many people soon will begin a new or augmented running program. Many also will wind up sidelined by injury. But a new study suggests that being light on your feet could keep most runners healthy.

Running injuries are extremely common, with some statistics estimating that as many as 90 percent of runners miss training time every year due to injury.

But the underlying cause of many of these injuries remains in question. Past studies and popular opinion have blamed increased mileage, excess body weight, over-striding, modern running shoes, going barefoot, weak hips, diet, and rough pavement or trails. But most often, studies have found that the best indicator of a future injury is a past one, which, frankly, is not a helpful conclusion for runners hoping not to get hurt.

So for the new study, which was published in December in the British Journal of Sports Medicine, researchers at Harvard Medical School and other universities decided to look at running injuries, one of the more obvious but surprisingly understudied aspects of running, and to focus their attention, in part, on those rare long-time runners who have never been hurt.

Specifically, they set out to look at pounding, or impact loading, which means the amount of force that we create when we strike the ground. Pounding is, of course, inevitable during a run. But runners with similar body types and running styles can experience wildly different amounts of impact loading, and it hasn’t been clear to what extent these differences directly contribute to injuries.

The researchers recruited 249 experienced female recreational runners, who were chosen in part because they all struck the ground with their heels when they ran. Most runners are heel strikers, and heel striking is believed by many running experts to cause higher impacts than landing near the middle or front of the foot, possibly contributing to an increased risk of injuries. (The scientists focused on a single sex so that they would not have to control for gender in the results.)

The volunteers reported to the biomechanics lab at the Spaulding National Running Center, which is affiliated with Harvard Medical School, where they completed questionnaires about their injury history and then strode along a track equipped with force monitors to determine their impact loads.

Afterward, the scientists asked each volunteer to complete an ongoing, online running diary and injury log.

The researchers tracked the runners for two years.

During that time, more than 100 of the runners reported sustaining an injury that was serious enough to require medical attention. Another 40 or so reported minor injuries, while the rest remained uninjured.

More remarkably, in the minds of the researchers, 21 of the runners not only did not become injured during the two-year study but also had not had a prior injury. They remained long-term running-injury virgins, the athletic equivalent of unicorns.

Intrigued, the scientists decided to compare that small group’s impact loading with the pounding experienced by the seriously injured runners, since, the researchers theorized, the contrast between these groups should provide the most telling data about whether how hard you land affects your risk of being hurt.

The answer was that it does. The never-injured runners, as a group, landed far more lightly than those who had been seriously hurt, the scientists found, even when the researchers controlled for running mileage, body weight and other variables.

That finding refutes the widely held belief that a runner cannot land lightly on her heels.

“One of the runners we studied, a woman who has run multiple marathons and never been hurt, had some of the lowest rates of loading that we’ve ever seen,” said Irene Davis, a Harvard professor and director of the Spaulding center, who led the study. She pounded far less than many runners who land near the front of their feet, Dr. Davis said. “When you watched her run, it was like seeing an insect running across water. It was beautiful.”

The data also, however, contain a more general message for those of us who are not as wispy and whippy in our landings. Consciously think about “a soft landing,” Dr. Davis said. Some runners, especially those with a long history of injuries, might want to experiment with landing closer to the midfoot, she said, since many — but not all — runners naturally land more lightly when they don’t lead with the heel.

Consider, too, slightly increasing your cadence, she said, which is the number of steps you take per minute, a change that also tends to reduce the pounding from each stride. Or you might, as I plan to do, imagine that you are running over eggshells or, even more evocatively, are a water strider, moving gracefully and weightlessly across the pond.

Related:

For more fitness, food and wellness news, follow us on Facebook and Twitter, or sign up for our newsletter.

A Diet and Exercise Plan to Lose Weight and Gain Muscle

Photo

Credit Getty Images

If there is a holy grail of weight loss, it would be a program that allows someone to shed fat rapidly while hanging on to or even augmenting muscle. Ideally, it would also be easy.

A new study describes a workout and diet regimen that accomplishes two of those goals remarkably well. But it may not be so easy.

For most of us, losing weight and keeping it off is difficult. If you consume fewer calories than your body requires for daily operations, it turns to internal sources of fuel. Those sources consist of body fat and lean tissue, meaning muscle. When someone on a diet drops a pound of body mass (a measure that does not include water), much of that pound consists of fat. But about a third or more can be made up of muscle.

The problem with losing muscle is that, unlike fat tissue, muscle burns calories. Having less muscle means a lower resting metabolic rate, so you burn fewer calories throughout the day. Losing muscle may also discourage physical activity, which is important for maintaining weight loss.

So researchers have long been looking for weight loss programs that produce hefty amounts of fat loss but diminish any decline in muscle.

For scientists at McMaster University in Ontario, Canada, that goal seemed to demand a high dose of protein and also plenty of exercise.

As the scientists knew, amino acids in protein help muscle tissue to maintain itself and to grow. Many past studies have suggested that low-calorie but high-protein diets can result in less muscle loss than the same number of calories but less protein.

However, the best dosage of protein in these circumstances has remained unclear, as has the role, if any, for exercise.

So for the new study, which was published in The American Journal of Clinical Nutrition, the McMaster researchers rounded up 40 overweight young men who were willing to commit to an intensive weight-loss program and divided them in half.

All of the young men began a diet in which their daily calories were cut by about 40 percent (compared to what they needed to maintain weight). But for half of them, this consisted of about 15 percent protein, 35 percent fat and 50 percent carbohydrates.

The other 20 volunteers began a diet that mimicked that of the first group, except that theirs swapped the protein and fat ratios, so that 35 percent of their calories came from protein and 15 percent from fat. Over all, their protein intake was about three times the recommended dietary allowance for most people.

The researchers handled that switch by changing the make-up of a supplied drink. In the low-protein group, the beverage contained high-fat milk and no added protein. For the others, it consisted of low-fat milk and a large dollop of whey protein.

All of the men also began a grueling workout routine. Six days a week they reported to the exercise lab and completed a strenuous full-body weight training circuit, high-intensity intervals, or a series of explosive jumps and other exercises known as plyometric training.

The diet and exercise routine continued for four weeks, by the end of which time, “those guys were done,” said Stuart Phillips, who holds a research chair in skeletal muscle health at McMaster University and oversaw the study. “All they could talk about was food.”

The routine had succeeded in incinerating pounds from all of the participants. The men in both groups weighed about 11 or 12 pounds less, on average.

But it was the composition of that weight loss that differed. Unlike most people on low-calorie diets, the men on the high-protein regimen had actually gained muscle during the month, as much as three pounds of it. So in these men, almost all of the 11 or 12 pounds they had lost over all had been fat.

These results strongly suggest that extra protein is advisable during weight loss, Dr. Phillips said, to avoid stripping yourself of muscle.

But exercise is also key, Dr. Phillips continued, particularly weight training, since it is known to build muscle. Even the men on the lower-protein diet lost little muscle mass, he pointed out, which was unexpected and almost certainly due, he and his colleagues concluded, to exercise.

Of course, by the end of the month, none of the men wished to continue. This type of extreme calorie cutting combined with intense exercise “is not a sustainable program in the long term,” Dr. Phillips said. “It’s more a kind of boot camp,” he said, manageable in the short term by people who are very committed and generally very healthy.

He and his colleagues plan to conduct follow-up experiments to find a more realistic and sustainable program. They plan, too, to study female volunteers and play around with the diets’ composition, to establish definitively that it is extra protein and not reduced fat that promotes muscle gains.

In the meantime, for those hoping to become thin but not puny, various apps allow you to determine the percentage of your diet that is composed of protein. If it is below 10 or 15 percent, you might want to shift calories from fat to protein. Renew your gym membership, too.

Related:

For more fitness, food and wellness news, follow us on Facebook and Twitter, or sign up for our newsletter.