Caffeine pill 'could boost memory; Coffee 'may reverse Alzheimer's'

Caffeine pill 'could boost memory'
BBC News
12 January 2014

Sleep 'cleans' the brain of toxins
Memory 'more consistent with age'
Coffee 'may reverse Alzheimer's'
A US study has raised the possibility that we may one day rely on caffeine to boost memory as well as to wake up.

The research, published in Nature Neuroscience, tested the memories of 160 people over 24 hours.

It found those who took caffeine tablets, rather than dummy pills, fared better on the memory tests.

But experts warned people to remember caffeine could cause negative effects, such as jitteriness and anxiety.

The Johns Hopkins University study involved people who did not regularly eat or drink caffeinated products.

Saliva samples were taken, to check base levels of caffeine, then participants were asked to look at a series of images.

Five minutes later they were given either a 200-milligram caffeine tablet - equivalent to the caffeine in a large cup of coffee, according to the researchers - or a dummy pill.

Saliva samples were taken again one, three and 24 hours later.

The next day, both groups were also tested on their ability to recognise the previous day's images.

Altered images

Twenty-four hours may not sound like a long time, but it is in terms of memory studies. Most "forgetting" happens in the first few hours after learning something.

People were purposely shown a mixture of some of the initial tranche of images, some new - and some that were subtly different.

Being able to distinguish between similar, but not identical items, is called pattern separation and indicates a deeper level of memory retention.

More members of the caffeine group were able to correctly identify "similar" images, rather than wrongly saying they were the same.

"Our study suggests that 200mg of coffee is beneficial to those who do not regularly ingest caffeine”

Prof Michael Yassa Johns Hopkins University

Prof Michael Yassa, who led the study, said: "If we used a standard recognition memory task without these tricky similar items, we would have found no effect of caffeine.

"However, using these items requires the brain to make a more difficult discrimination - what we call pattern separation, which seems to be the process that is enhanced by caffeine in our case."

Only a few previous studies have been carried out into caffeine's effect on long-term memory, and those that have been done generally found little effect.

This study was different because people took the caffeine after, rather than before, they had seen and attempted to memorise the images.

The team now want to look at what happens in the hippocampus, the "memory centre" of the brain, so they can understand caffeine's effect.

Moderation But Prof Yassa said their findings do not mean people should rush out and drink lots of coffee, eat lots of chocolate - or take lots of caffeine pills.

"Everything in moderation. Our study suggests that 200mg of coffee is beneficial to those who do not regularly ingest caffeine.

"But we also show an inverted U-shape dose response suggesting that higher doses may not be as beneficial.

If you take too much caffeine there could be negative consequences for the body”

Dr Ashok Jansari University of East London

"Keep in mind that if you're a regular caffeine drinker this amount may change."

He added: "There are of course health risks to be aware of.

"Caffeine can have side effects like jitteriness and anxiety in some people. The benefits have to be weighed against the risks."

Dr Anders Sandberg from the Future of Humanity Institute at the University of Oxford, said: "The paper demonstrates that giving caffeine after seeing images does improve recognition of them 24 hours later, supporting the idea that it helps the brain consolidate the learning.

"However, there was no straight improvement in recognition memory thanks to caffeine. Rather, the effect was a small improvement in the ability to distinguish new images that looked like old, from the real old images."

He added: "Caffeine may still be helpful for paying attention to what you are studying and hence help your encoding, but the best way of boosting consolidation is sleep - which might be a problem in this case, if you take the caffeine too close to bedtime.

Dr Ashok Jansari, from the University of East London's school of psychology, said caffeine appeared to "sharpen" memory, rather than actually making it better.

He said: "I would definitely not advise that people start taking in as much caffeine as possible since in terms of memory anything above 200mg may not help much and if you take too much caffeine there could be negative consequences for the body."

Coffee 'may reverse Alzheimer's'
BBC News
5 July 2009


A possible treatment for dementia?

Drinking five cups of coffee a day could reverse memory problems seen in Alzheimer's disease, US scientists say.

The Florida research, carried out on mice, also suggested caffeine hampered the production of the protein plaques which are the hallmark of the disease. Previous research has also suggested a protective effect from caffeine. But British experts said the Journal of Alzheimer's disease study did not mean that dementia patients should start using caffeine supplements. The results are particularly exciting in that a reversal of pre-existing memory impairment is more difficult to achieve Dr Gary Arendash University of South Florida The 55 mice used in the University of South Florida study had been bred to develop symptoms of Alzheimer's disease. First the researchers used behavioural tests to confirm the mice were exhibiting signs of memory impairment when they were aged 18 to 19 months, the equivalent to humans being about 70. Then they gave half the mice caffeine in their drinking water. The rest were given plain water. The mice were given the equivalent of five 8 oz (227 grams) cups of coffee a day - about 500 milligrams of caffeine. The researchers say this is the same as is found in two cups of "specialty" coffees such as lattes or cappuccinos from coffee shops, 14 cups of tea, or 20 soft drinks. When the mice were tested again after two months, those who were given the caffeine performed much better on tests measuring their memory and thinking skills and performed as well as mice of the same age without dementia. Those drinking plain water continued to do poorly on the tests. In addition, the brains of the mice given caffeine showed nearly a 50% reduction in levels of the beta amyloid protein, which forms destructive clumps in the brains of dementia patients. Further tests suggested caffeine affects the production of both the enzymes needed to produce beta amyloid. The researchers also suggest that caffeine suppresses inflammatory changes in the brain that lead to an overabundance of the protein. Earlier research by the same team had shown younger mice, who had also been bred to develop Alzheimer's but who were given caffeine in their early adulthood, were protected against the onset of memory problems. 'Safe drug' Dr Gary Arendash, who led the latest study, told the BBC: "The results are particularly exciting in that a reversal of pre-existing memory impairment is more difficult to achieve. "They provide evidence that caffeine could be a viable 'treatment' for established Alzheimer's disease and not simply a protective strategy. "That's important because caffeine is a safe drug for most people, it easily enters the brain, and it appears to directly affect the disease process." The team now hope to begin human trials of caffeine to see if the mouse findings are replicated in people. They do not know if a lower amount of caffeine would be as effective, but said most people could safely consume the 500 milligrams per day. However they said people with high blood pressure, and pregnant women, should limit their daily caffeine intake. Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: "In this study on mice with symptoms of Alzheimer's, researchers found that caffeine boosted their memory. We need to do more research to find out whether this effect will be seen in people. "It is too early to say whether drinking coffee or taking caffeine supplements will help people with Alzheimer's. Neil Hunt, chief executive of the Alzheimer's Society, said previous research into caffeine had suggested it could delay Alzheimer's disease and even protect against vascular dementia. "This research in mice suggests that coffee may actually reverse some element of memory impairment. "However much more research is needed to determine whether drinking coffee has the same impact in people. "It is too soon to say whether a cup of coffee is anything more than a pleasant pick me up."

Mediterranean diet may protect against diabetes

Mediterranean diet may protect against diabetes
By Andrew M. Seaman
Mon Jan 6, 2014
(Reuters Health)

Without cutting back on calories, adopting a Mediterranean diet rich in extra-virgin olive oil may protect people at high risk for heart disease against diabetes, a new study found. Researchers who analyzed data on more than 3,500 people at an increased risk for heart disease found those who were put on a Mediterranean diet were about 30 percent less likely to develop diabetes over the next four years, compared to those assigned to a general low-fat diet. "Randomized trials have shown that lifestyle interventions promoting weight loss can reduce the incidence of type 2 diabetes, however, whether dietary changes without calorie restriction or increased physical activity also protect from diabetes development has not been evaluated in the past," Dr. Jordi Salas-Salvado wrote to Reuters Health in an email. Salas-Salvado is the study's lead author and a professor of nutrition at Rovira i Virgili University and the head of the Department of Nutrition at the Hospital de Sant Joan de Reus in Spain. Previous research, including another study from Salas-Salvado and colleagues, suggested Mediterranean diets may be protective against diabetes (see Reuters Health story of October 14, 2010 here: reut.rs/1i7Rx5W. Mediterranean diets are generally high in vegetables, fiber-rich grains, legumes, fish and plant-based sources of unsaturated fat - particularly olive oil and nuts. They are low in red meat and high-fat dairy, prime sources of saturated fat. In addition to being touted as beneficial to people with heart disease, Mediterranean diets are believed to have components that reduce inflammation throughout the body and may have some impact on diabetes. Type 2 diabetes, sometimes referred to as adult-onset diabetes, is when the body's cells are resistant to insulin or the body doesn't make enough of the hormone, so glucose remains in the bloodstream and can climb to dangerously high levels. Insulin gives glucose - or blood sugar - access to the body's cells to be used as fuel. For the new study, published in the Annals of Internal Medicine, the researchers used data from an existing trial that compared the effectiveness of Mediterranean-style diets to a low-fat diet. Between 2003 and 2009, 3,541 Spaniards ages 55 to 80 were enrolled in the trial. None of the participants had diabetes at the start of the trial, but all had three or more risk factors for heart disease. Those include smoking, being overweight and having high cholesterol. The participants were randomly assigned to adopt one of three diets. One diet consisted of a Mediterranean diet that derived most of its unsaturated fat from extra-virgin olive oil. Another group was assigned a Mediterranean diet that used mixed nuts as its main source of unsaturated fat. The third diet emphasized reducing all fat consumption. None of the diets, however, asked the participants to cut down on how many calories they ate or to increase how much they exercised. After about four years, 273 of the participants had developed diabetes. That included 6.9 percent of participants from the extra-virgin olive oil group, 7.4 percent from the mixed nuts group and 8.8 percent from the reduced-fat group. The researchers caution that the difference in diabetes cases among people on the mixed nuts and reduced-fat diets may have been due to chance. They can't explain why the mixed nuts diet didn't show quite the same benefit as the extra-virgin olive oil diet. But Salas-Salvado said the difference between the two Mediterranean diets could also be a coincidence, because both have additional unsaturated fatty acids that are linked to a reduced diabetes risk. He said cutting calories along with adopting a Mediterranean-style diet would likely reduce risks even further. "These benefits have been observed in participants between 55 to 80 years old at high cardiovascular risk," he said. "Therefore, the message is that it is never too late to switch to a healthy diet like the Mediterranean." SOURCE: bit.ly/SQRXAa Annals of Internal Medicine, online January 6, 2014.

More than two drinks a day could speed memory loss: study

More than two drinks a day could speed memory loss: study
GMA News
January 16, 2014

WASHINGTON - Men who consume more than two alcoholic drinks per day while in middle age may speed up their memory loss in later life by up to six years, said a study Wednesday.

However, there were no differences in memory or mental function between non-drinkers and those who drank less than two drinks, or 20 grams per day, said the findings in the journal Neurology.

For the study, more than 5,000 middle-aged men were interviewed about their drinking habits three times over 10 years.

Then, they underwent memory and other cognitive tests beginning at an average age of 56. These tests were repeated twice over the next 10 years.

"Our study focused on middle-aged participants and suggests that heavy drinking is associated with faster decline in all areas of cognitive function in men," said study author Severine Sabia of the University College London.

The mental abilities of heavy drinkers declined between one-and-a-half to six years faster than those who had fewer drinks per day.

Men who drank 36 grams of alcohol or more per day saw the steepest declines in their memory and brain function.

Some 2,000 women were also included in the study, but there were not enough heavy drinkers among them to analyze their rates of mental decline compared to moderate or non-drinkers.

Neurology is the medical journal of the American Academy of Neurology. — Agence France-Presse

Vitamin E may aid those with mild to moderate Alzheimer's

Vitamin E may aid those with mild to moderate Alzheimer's
Karen Weintraub
USATODAY
December 31, 2013

Vitamin E is far from an Alzheimer's cure, but a new study finds it allowed trial participants to get less help from caregivers and therefore retain more independence longer.

Taking high doses of vitamin E appears to help people in all stages of Alzheimer's disease, a new study suggests.

Research a decade ago showed that vitamin E was helpful in late-stage Alzheimer's disease. Now a study published Tuesday by the Journal of the American Medical Association finds the benefits extend to people with mild to moderate forms of the disease.

"This looks very promising," said lead researcher Mary Sano, director of the Alzheimer's Disease Research Center at the James J. Peters VA Medical Center, and the Icahn School of Medicine at Mount Sinai, both in New York City.

Vitamin E is far from a cure, only somewhat improving functional activities such as planning and organizing, the study found. But it did allow trial participants, who were studied for an average of more than two years, to get less help from caregivers and therefore retain more independence longer.

"It's not something where you must do this, it's going to make all the difference," said Rachelle Doody, director of the Alzheimer's Disease and Memory Disorders Center at Baylor College of Medicine in Houston. But Doody, who was not involved in the current study, said she thinks it's worthwhile for most Alzheimer's patients, in consultation with their doctor, to take 2,000 IU of vitamin E per day.

That amount far exceeds the government's recommended dose for healthy adults, which is 22.4 IU or 15 mg per day. There is no indication that high doses of vitamin E help healthy adults, and research shows an increased risk of death with such high doses, particularly for people with congestive heart failure.

That's why Heather Snyder, Director of Medical & Scientific Relations at the Alzheimer's Association, thinks that people with mild to moderate Alzheimer's should wait for more research before jumping to add vitamin E to their pill box.

The new study looked at patients in the Veteran's Affairs system, so they were virtually all male. It's not yet clear, Snyder said, that the benefits of vitamin E will be true for women as well.

It's also unclear why high doses of vitamin E would help people with Alzheimer's, Snyder said, so the Alzheimer's Association is funding research to uncover a possible mechanism. Vitamin E is a so-called antioxidant, meaning it combats the damage that oxygen does to cells. It also stabilizes cell membranes. Perhaps, Doody said, at very high doses, enough vitamin E reaches the brain to protect against the brain cell death that characterizes Alzheimer's. Doody, who has done her own research into Alzheimer's and vitamin E, believes the vitamin is safe and life-extending for people with the memory disease. The new study also examined a drug called memantine, which is already used to treat advanced Alzheimer's, but found no benefit to mild-to-moderate Alzheimer's patients from the drug alone or in connection with high doses of vitamin E. All of the 600 patients in the trial were also prescribed the standard-of-care drugs, called cholinesterase inhibitors, although Sano said she thinks vitamin E will also benefit patients who are not taking those drugs.

Heavy drinking will literally rot your DNA

Heavy drinking will literally rot your DNA
Even occasional heavy drinking can have long-lasting impacts
National Monitor
Ian Lang
January 02, 2014

For some, college wouldn’t be worth attending were it not for the weekend alcohol benders: Week-long bouts of studiousness bookended by weekends of debauchery and heavy drinking. Provided you lay off the sauce more often than not, letting loose a couple of days per week never hurt anyone, right? Wrong. According to a new study, even sporadic instances of heavy drinking can damage DNA.

Coming out of Mexico, the study worked with university students to analyze the effect of weekend alcohol consumption on the lipids comprising cell membrane and its genetic material, i.e. DNA. This is the first study of its kind to examine the effect of alcohol on DNA during the early stages of alcohol abuse. Earlier studies ignored it, likely because they focused on subjects who had consumed alcohol in an addictive manner for some time.

Oddly enough, researcher Adela Rendón was prompted to launch the study when she observed college students acting like college students. While lecturing Clinical Biochemistry on a Monday morning, she noticed that students who had drank over the weekend were inattentive and out of sorts. She suspected that this was due to alcohol consumption and not because “Clinical Biochemistry” sounds like the most boring subject on Earth. She involved the students and went ahead with gathering experts and completing necessary administrative documents.

The eventual aim of the study? Oxidative damage caused by the consumption of alcohol beverages in young people.

The activity of the alcohol enzyme dehydrogenase, responsible for metabolizing ethanol into acetaldehyde, acetoacetate and acetone was measured. Oxidative damage is evaluated by a TBARS biochemical test (types that react to barbituric acid), and reflects the lipid peroxidation that affects the membrane due to the impact not only of the ethanol in the blood but also of the acetaldehyde produced by the action of the enzyme on the ethanol. That means there are at least two means by which free radicals are formed and which can damage cell membrane integrity.

Researchers were surprised not because they found results, but by the volume of those results.

“We saw that the ones who drank sustained twice as much oxidative damage compared with the group that did not consume alcohol,” Rendón said. Further examining cells via the “comet test” (used to measure damage to cell DNA), they found that students who drank had 5.3 times the number of damaged cells as those who abstained.

Scientists expect to observe that kind of damage in chronic alcohol abusers, but were surprised to see any damage at all stemming from a comparatively isolated instance of drinking.

“When we talk about youth alcohol abuse, we are referring to youngsters who drink alcohol without having become addicted. Addiction involves a more complex issue socially and psychologically speaking. This is social alcohol abuse,” said Rendón, “but which causes damage in the long term and you have to be aware of that.”

The harmful consumption of alcoholic beverages is a global issue and constitutes a significant health, social and economic problem. According to World Health Organisation data, alcohol is responsible for 2.5 million deaths a year worldwide and drinkers between the ages of 19 and 25 account for 320,000 of them...

Brain scans found seniors with both poor memory and prior head injury have more plaque buildup

Brain scans found seniors with both poor memory and prior head injury have more plaque buildup
WebMD News from HealthDay
By Kathleen Doheny
Dec. 26, 2013

(HealthDay News) -- Older adults with memory problems and a history of concussion have more buildup of Alzheimer's disease-associated plaques in the brain than those who also had concussions but don't have memory problems, according to a new study.v
''What we think it suggests is, head trauma is associated with Alzheimer's-type dementia -- it's a risk factor," said study researcher Michelle Mielke, an associate professor of epidemiology and neurology at Mayo Clinic Rochester. "But it doesn't mean someone with head trauma is [automatically] going to develop Alzheimer's."

Her study is published online Dec. 26 and in the Jan. 7 print issue of the journal Neurology.

Previous studies looking at whether head trauma is a risk factor for Alzheimer's have come up with conflicting results, she noted. And Mielke stressed that she has found only a link or association, not a cause-and-effect relationship.

In the study, Mielke and her team evaluated 448 residents of Olmsted County, Minn., who had no signs of memory problems. They also evaluated another 141 residents with memory and thinking problems known as mild cognitive impairment. More than 5 million Americans have Alzheimer's disease, according to the Alzheimer's Association. Plaques are deposits of a protein fragment known as beta-amyloid that can build up in between the brain's nerve cells. While most people develop some with age, those who develop Alzheimer's generally get many more, according to the Alzheimer's Association. They also tend to get them in a predictable pattern, starting in brain areas crucial for memory. In the Mayo study, all participants were aged 70 or older. The participants reported if they ever had a brain injury that involved loss of consciousness or memory. Of the 448 without any memory problems, 17 percent had reported a brain injury. Of the 141 with memory problems, 18 percent did. This suggests that the link between head trauma and the plaques is complex, Mielke said, as the proportion of people reporting concussion was the same in both groups. Brain scans were done on all the participants. Those who had both concussion history and cognitive [mental] impairment had levels of amyloid plaques that were 18 percent higher than those with cognitive impairment but no head trauma history, the investigators found. Among those with mild cognitive impairment, those with concussion histories had a nearly five times higher risk of elevated plaque levels than those without a history of concussion. The researchers don't know why some with concussion history develop memory problems and others do not. The research was funded by the U.S. National Institutes of Health, among several other supporters.Brain scans found seniors with both poor memory and prior head injury have more plaque buildup Share this: Font size: AAA WebMD News from HealthDay New guidelines address which patients might By Kathleen Doheny HealthDay Reporter THURSDAY, Dec. 26, 2013 (HealthDay News) -- Older adults with memory problems and a history of concussion have more buildup of Alzheimer's disease-associated plaques in the brain than those who also had concussions but don't have memory problems, according to a new study. ''What we think it suggests is, head trauma is associated with Alzheimer's-type dementia -- it's a risk factor," said study researcher Michelle Mielke, an associate professor of epidemiology and neurology at Mayo Clinic Rochester. "But it doesn't mean someone with head trauma is [automatically] going to develop Alzheimer's." Her study is published online Dec. 26 and in the Jan. 7 print issue of the journal Neurology. Previous studies looking at whether head trauma is a risk factor for Alzheimer's have come up with conflicting results, she noted. And Mielke stressed that she has found only a link or association, not a cause-and-effect relationship. In the study, Mielke and her team evaluated 448 residents of Olmsted County, Minn., who had no signs of memory problems. They also evaluated another 141 residents with memory and thinking problems known as mild cognitive impairment. More than 5 million Americans have Alzheimer's disease, according to the Alzheimer's Association. Plaques are deposits of a protein fragment known as beta-amyloid that can build up in between the brain's nerve cells. While most people develop some with age, those who develop Alzheimer's generally get many more, according to the Alzheimer's Association. They also tend to get them in a predictable pattern, starting in brain areas crucial for memory. In the Mayo study, all participants were aged 70 or older. The participants reported if they ever had a brain injury that involved loss of consciousness or memory. Of the 448 without any memory problems, 17 percent had reported a brain injury. Of the 141 with memory problems, 18 percent did. This suggests that the link between head trauma and the plaques is complex, Mielke said, as the proportion of people reporting concussion was the same in both groups. Brain scans were done on all the participants. Those who had both concussion history and cognitive [mental] impairment had levels of amyloid plaques that were 18 percent higher than those with cognitive impairment but no head trauma history, the investigators found. Among those with mild cognitive impairment, those with concussion histories had a nearly five times higher risk of elevated plaque levels than those without a history of concussion. The researchers don't know why some with concussion history develop memory problems and others do not. The research was funded by the U.S. National Institutes of Health, among several other supporters. The study adds valuable information for experts in the field, said Dr. Robert Glatter, director of sports medicine and traumatic brain injury in the department of emergency medicine at Lenox Hill Hospital, in New York City. Glatter, who is also a former sideline physician for the National Football League's New York Jets, reviewed the new study findings. The study adds valuable information for experts in the field, said Dr. Robert Glatter, director of sports medicine and traumatic brain injury in the department of emergency medicine at Lenox Hill Hospital, in New York City. Glatter, who is also a former sideline physician for the National Football League's New York Jets, reviewed the new study findings.

It seems that four times a week may be the ideal workout schedule

There were, remarkably, almost no differences in fitness gains among the groups. The women working out twice a week had become as powerful and aerobically fit as those who had worked out six times a week. There were no discernible differences in cytokine levels among the groups, either.

However, the women exercising four times per week were now expending far more energy, over all, than the women in either of the other two groups. They were burning about 225 additional calories each day, beyond what they expended while exercising, compared to their calorie burning at the start of the experiment.

The twice-a-week exercisers also were using more energy each day than they had been at first, burning almost 100 calories more daily, in addition to the calories used during workouts.

But the women who had been assigned to exercise six times per week were now expending considerably less daily energy than they had been at the experiment’s start, the equivalent of almost 200 fewer calories each day, even though they were exercising so assiduously.

“We think that the women in the twice-a-week and four-times-a-week groups felt more energized and physically capable” after several months of training than they had at the start of the study, says Gary Hunter, a U.A.B. professor who led the experiment. Based on conversations with the women, he says he thinks they began opting for stairs over escalators and walking for pleasure.

The women working out six times a week, though, reacted very differently. “They complained to us that working out six times a week took too much time,” Dr. Hunter says. They did not report feeling fatigued or physically droopy. Their bodies were not producing excessive levels of cytokines, sending invisible messages to the body to slow down.

Rather, they felt pressed for time and reacted, it seems, by making choices like driving instead of walking and impatiently avoiding the stairs.

Why Four Workouts a Week May Be Better Than Six
By GRETCHEN REYNOLDS
New York Times
February 13, 2013

A common concern about exercise is that if you don’t do it almost every day, you won’t achieve much health benefit. But a commendable new study suggests otherwise, showing that a fairly leisurely approach to scheduling workouts may actually be more beneficial than working out almost daily.

For the new study, published this month in Medicine & Science in Sports & Exercise, researchers at the University of Alabama at Birmingham gathered 72 older, sedentary women, ages 60 to 74, and randomly assigned them to one of three exercise groups.

One group began lifting weights once a week and performing an endurance-style workout, like jogging or bike riding, on another day.

Another group lifted weights twice a week and jogged or rode an exercise bike twice a week.

The final group, as you may have guessed, completed three weight-lifting and three endurance sessions, or six weekly workouts.

The exercise, which was supervised by researchers, was easy at first and meant to elicit changes in both muscles and endurance. Over the course of four months, the intensity and duration gradually increased, until the women were jogging moderately for 40 minutes and lifting weights for about the same amount of time.

The researchers were hoping to find out which number of weekly workouts would be, Goldilocks-like, just right for increasing the women’s fitness and overall weekly energy expenditure.

Some previous studies had suggested that working out only once or twice a week produced few gains in fitness, while exercising vigorously almost every day sometimes led people to become less physically active, over all, than those formally exercising less. Researchers theorized that the more grueling workout schedule caused the central nervous system to respond as if people were overdoing things, sending out physiological signals that, in an unconscious internal reaction, prompted them to feel tired or lethargic and stop moving so much.

To determine if either of these possibilities held true among their volunteers, the researchers in the current study tracked the women’s blood levels of cytokines, a substance related to stress that is thought to be one of the signals the nervous system uses to determine if someone is overdoing things physically. They also measured the women’s changing aerobic capacities, muscle strength, body fat, moods and, using sophisticated calorimetry techniques, energy expenditure over the course of each week.

By the end of the four-month experiment, all of the women had gained endurance and strength and shed body fat, although weight loss was not the point of the study. The scientists had not asked the women to change their eating habits.

There were, remarkably, almost no differences in fitness gains among the groups. The women working out twice a week had become as powerful and aerobically fit as those who had worked out six times a week. There were no discernible differences in cytokine levels among the groups, either.

However, the women exercising four times per week were now expending far more energy, over all, than the women in either of the other two groups. They were burning about 225 additional calories each day, beyond what they expended while exercising, compared to their calorie burning at the start of the experiment.

The twice-a-week exercisers also were using more energy each day than they had been at first, burning almost 100 calories more daily, in addition to the calories used during workouts.

But the women who had been assigned to exercise six times per week were now expending considerably less daily energy than they had been at the experiment’s start, the equivalent of almost 200 fewer calories each day, even though they were exercising so assiduously.

“We think that the women in the twice-a-week and four-times-a-week groups felt more energized and physically capable” after several months of training than they had at the start of the study, says Gary Hunter, a U.A.B. professor who led the experiment. Based on conversations with the women, he says he thinks they began opting for stairs over escalators and walking for pleasure.

The women working out six times a week, though, reacted very differently. “They complained to us that working out six times a week took too much time,” Dr. Hunter says. They did not report feeling fatigued or physically droopy. Their bodies were not producing excessive levels of cytokines, sending invisible messages to the body to slow down.

Rather, they felt pressed for time and reacted, it seems, by making choices like driving instead of walking and impatiently avoiding the stairs.

Despite the cautionary note, those who insist on working out six times per week need not feel discouraged. As long as you consciously monitor your activity level, the findings suggest, you won’t necessarily and unconsciously wind up moving less over all.

But the more fundamental finding of this study, Dr. Hunter says, is that “less may be more,” a message that most likely resonates with far more of us. The women exercising four times a week “had the greatest overall increase in energy expenditure,” he says. But those working out only twice a week “weren’t far behind.”